MEKELLE -UNIVERSITY

SCHOOL of MECHANICAL and INDUSTRIAL ENGINEERING

DEPARTMENT of MECHANICAL ENGINEERING
THESIS on
DESIGN of SOLAR COOLING SYSTEM for AIR HANDLING UNITS
of GMARMENT ROOM’S AC SYSTEM

PREPARED BY:
G/HANNES TENSAY EIT /UR 1460/03
KINDALEM TESFA EIT/UR 1963/03

ADVISOR NAME
Mr. YACOB G/ YOHANS
JUNE, 2015G.C

Purpose: the purpose of the thesis will design solar cooling system for air handling unit of
magarment room’s AC system with cooling capacity of411.93TR (1350KW) with an effect
single absorption chillers that must be done under daily changing condition.

I. Abstract
 DESIGN of SOLAR COOLING SYSTEM for AIR 2015
HANDLING UNITS of GARMENT ROOMS’ AC SYSTEM

Modern cooling system (solar vapour absorption refrigeration system) has many
applications not only air handling unit of MAGARMENT room’s air conditioning system
but it is applicable for other status such as preserving medicine, blood and the most
important application, the preservation of food. It helped most foods keep at room
temperature spoil rapidly. Nearly half of the vaccines in developing countries go to waste
every year due to temperature spoilage, according to the World Health Organization. In our
country Ethiopia too, these problems are seen visibly. They can be eradicated or reduced by
using solar technology for remote applications as well as industrial factories. To solve this
problem, we designed a solar cooling system (absorption refrigerator) for Magarment
room’s AC system. This work contains the general introduction, problem statement,
objectives, scope of the study, significance the study expected outcome of the thesis in the
first chapter.
In the second chapter, literatures related to our work are revised.

The third chapter elaborates selection of solar cooling system components and their
criteria’s such as condenser, evaporator expansion valve, heat exchanger, the accessory like
rectifier and housing and solution pump (bubble pump).

The fourth chapter includes conceptual design such as the basic earth sun angle geometry,
design processing of parabolic trough thermal collector and conceptual thermal analysis of
the cycle is given in the form of table.

Fifth chapter contains design analysis to use ammonia water solution as a working fluid
pairs( binary mixture).The component design includes solar collector only, but the rest
components such as the generator, air-cooled heat exchangers condenser, evaporator and
absorber), valves, piping are selected components. This chapter is also included the cooling
load calculation and its data in the form of tables which gathered from garment rooms in
Quiha.

The sixth chapter includes conclusion and recommendation of the study

II. Acknowledgement

G/HANNES T. And KINDALEM T. Page ii

 DESIGN of SOLAR COOLING SYSTEM for AIR 2015
HANDLING UNITS of GARMENT ROOMS’ AC SYSTEM

First and foremost, we would like to thank our Lord Jesus Christ for he has made us do this
research (thesis) in a success way.

Secondly, we would like to pass our gratitude to our advisor Mr. Yacob Gebreyohanns for
his continuous support, patience, help, suggestion and courage he has given us for the
successful completion of the thesis. As a mentor he taught us a lot more than the thesis at
hand. We would like to extend our sincerely appreciation and we then want to thank all
mechanical engineering G.C students for their moral and material help and advice as friends.

Thirdly we would like to express our appreciation for our friends, Emuru, Yabsra bekele
andTeame Gebru and Merhatu Girmay who gave us their accessory.

Next, we would like to express our thanks to our family for their encouragement and support
throughout the study.

III. Acronym (Abbreviation)

A Absorber

G/HANNES T. And KINDALEM T. Page iii

 DESIGN of SOLAR COOLING SYSTEM for AIR 2015
HANDLING UNITS of GARMENT ROOMS’ AC SYSTEM

AC Air conditioning

AFM Air flow rate

Al aluminium

ASHRAE American Society of Heating, Refrigerating and Air Conditioning Engineers

C Condenser

CLTD Cooling Load Temperature Difference for glass in 0c

CLTDcorr Cooling Load Temperature Difference correction glass in 0c

CLF Cooling load factor

COP Coefficient of Performance

Cu Copper

CPEV Constant pressure expansion valve

E Evaporator

EV Expansion valve

G Generator

PS Solution pump

PTSC parabolic trough solar collector

HXE Heat exchanger

RSHF Room sensible heat gain factor

TEV Thermostatic expansion valve

VAR S Vapour Absorption refrigeration system

VCRS Vapour Compression Refrigeration System

Contents
I.Abstract............................................................................................i

G/HANNES T. And KINDALEM T. Page iv

 DESIGN of SOLAR COOLING SYSTEM for AIR 2015
HANDLING UNITS of GARMENT ROOMS’ AC SYSTEM

II.Acknowledgement.........................................................................ii
III.Acronym (Abbreviation)...........................................................iii
List of table........................................................................................x
IV.List of figure...............................................................................xii
Introduction.......................................................................................1
1. 1Back ground of the study...........................................................................1
1.2Problem statement.......................................................................................2
1.3 Objective of the project..............................................................................2
1.3.1 General objective.........................................................................................2
1.3.2 Specific objective of the project...................................................................3
1.4 Methodology..............................................................................................3
1.5 Significance of the project.........................................................................4
1.6 Scope of the project...................................................................................5
1.7 Expected outcome of the project................................................................5
Literature review...............................................................................6
2.1 Solar energy...............................................................................................6
2.1.1 Devices for solar thermal collections...........................................................6
2.1.2 Application of solar energy in cooling system.............................................7
2.1.2 Instrument for measuring solar radiation.....................................................8
2.1.3Types of instrument......................................................................................9
2. 2Solar cooling system................................................................................10
2.2. 1Thermal (work driven system)...................................................................10
2.2.2 Electricity (Photovoltaic) driven system....................................................10
2.2.3 Active solar cooling technique:..................................................................13
2.2.4 Passive solar cooling techniques...............................................................13
2.2.5 Intermittent cooling type............................................................................14
2.2.6 Continuous cooling type............................................................................14
2.2.7Solar vapours absorption cooling (refrigeration) system............................14
2.2.8 Compression refrigeration system..............................................................22
2.3 Working fluid for absorption refrigeration systems.................................24

G/HANNES T. And KINDALEM T. Page v

 DESIGN of SOLAR COOLING SYSTEM for AIR 2015
HANDLING UNITS of GARMENT ROOMS’ AC SYSTEM

2.4 Properties of absorbent &refrigerant solution..........................................25

2.4.1 Properties of refrigerants............................................................................25
2.4.2 Properties of absorbents.............................................................................26
2.4.3 for absorbent refrigerant combination........................................................26
Selection of components for solar absorption cooling system.....30
3.1 Condenser................................................................................................30
3.2Types of condensers..................................................................................31
3.2.1Air cooled condenser..................................................................................31
3.2.2Water cooled condenser..............................................................................31
3.2.3 Evaporative condenser...............................................................................32
3.3 Expansion valve.......................................................................................35
3.4 Types of expansion valves.......................................................................35
3.4.1Capillary tube.............................................................................................35
3.4.2Thermostatic expansion valve (TEV).........................................................36
3.4.3 Constant pressure expansion valve (CPEV)...............................................37
3.5 Evaporator................................................................................................37
3.6Types of evaporators.................................................................................38
3.5.1 Direct expansion finned tube.....................................................................38
3.5.2 Shell and tube............................................................................................38
3.7 Heat exchanger.........................................................................................39
3.9 Types of heat exchangers.........................................................................39
3.9.1 Shell and tube heat exchanger....................................................................39
3.9.2 Plate heat exchanger..................................................................................39
3.10 Selecting criteria’s for heat exchangers.................................................40
3.11Absorber..................................................................................................40
3.12 Solution pump (bubble pump)...............................................................40
3.13 Generator................................................................................................41
3.12 Rectifier..................................................................................................42
3.13 Housing:.................................................................................................43
3.14 Piping selection......................................................................................43
3.15 solar thermal collectors..........................................................................45

G/HANNES T. And KINDALEM T. Page vi

 DESIGN of SOLAR COOLING SYSTEM for AIR 2015
HANDLING UNITS of GARMENT ROOMS’ AC SYSTEM

3.15.1 Flat plate collector...................................................................................45

3.15.2 The parabolic dish system........................................................................46
3.15.3the parabolic trough collector...................................................................48
Absorber cover...................................................................................................52
Thermal and Conceptual design analysis.......................................54
4.1Thermal analyses......................................................................................54
4.1.1 Governing equations..................................................................................54
4.1.2 Phases of the refrigerant and absorbent in the cycle..................................54
4.2 Conceptual design analysis......................................................................57
4.2.1 Basic earth sun angles................................................................................57
4.2.4 Daily extraterrestrial radiation on the horizontal surface...........................63
4.2.5 Beam radiation...........................................................................................64
4.2.6 Important parameters used for designing of parabolic trough solar collector
equipment...........................................................................................................64
Design analysis.................................................................................66
5.1Solar radiation data...................................................................................66
5.2Basic sun -earth angle calculation.............................................................66
5.2.1 Monthly average daily solar radiation (H) & daily average hourly solar
radiation.............................................................................................................. 69
5.2.2Daily average solar radiation on horizontal surface..............................70
5.2.4 Daily average solar radiation on tilted surface...........................................74
5.2.5 Daily average Beam radiation on tilted surface (DABRTS)......................74
5.3 Sizing of parabolic trough solar collector................................................75
5.3.1 Specification..............................................................................................75
5.4Data collection and thermal cooling load calculation for garment building in
Quiha..................................................................................................................80
5.4.1 Basic Information......................................................................................80
5.4. 2Cooling load calculation............................................................................85
5.4.3 Other thermal analyses...............................................................................98
5.6 Design summary....................................................................................106
Conclusion and recommendation................................................108

G/HANNES T. And KINDALEM T. Page vii

 DESIGN of SOLAR COOLING SYSTEM for AIR 2015
HANDLING UNITS of GARMENT ROOMS’ AC SYSTEM

6.1Conclusion..............................................................................................108
6.2 Recommendation...................................................................................109
Bibliography..................................................................................110
Appendices.....................................................................................113
Appendix-A-1..............................................................................................113
Appendix- A-2.............................................................................................114
Appendix- B-1.............................................................................................115
Appendix-B-2..............................................................................................115
Appendix-B-3..............................................................................................116
Appendix- B-4.............................................................................................117
Appendix- B-5.............................................................................................118

List of table
Table general characteristics of methods for radiant energy measurement..................8

G/HANNES T. And KINDALEM T. Page viii

 DESIGN of SOLAR COOLING SYSTEM for AIR 2015
HANDLING UNITS of GARMENT ROOMS’ AC SYSTEM

Table 2.2 comparison b/n VAR&VCR......................................................................24

Table 3.1types of condensers.................................................................................34

Table 4.1 absorption refrigeration calculation........................................................54

Table 4.2 mass and energy balance of each components.......................................56

Table 5.1 labour workers and office of garment rooms..............................................82

Table 5.2 working lights........................................................................................82

Table5.3 working machines.....................................................................................82

Table 5.4 sample rooms........................................................................................83

Table 5.4 for satellite store, pattern &design room quality office, marketing room,

Production area, general items store.......................................................................83

Table 5.6 windows.................................................................................................84

Table 5.7 walls...........................................................................................................84

Table 5.8 doors......................................................................................................85

Table 5.9 heat gain through glasses........................................................................89

Table 5.10 solar transmission.................................................................................90

Table 5.11 heat gain through doors..........................................................................92

Tale 5.12 place, NO of people................................................................................92

Tale 5.13 room, lights.............................................................................................93

Table 5.14 main rooms..............................................................................................94

Tale 5.15 sample rooms..............................................................................................95

Table 5.16 summary of cooling load calculation.....................................................97

Table 5.17 thermodynamic analysis summary..........................................................106

Table 5.18 dimensional designs output summary...................................................107

Table A-6-1water liquid –vapour saturation..........................................................116

Table A-8-1 ammonia liquid -vapour saturation...................................................117

G/HANNES T. And KINDALEM T. Page ix

 DESIGN of SOLAR COOLING SYSTEM for AIR 2015
HANDLING UNITS of GARMENT ROOMS’ AC SYSTEM

Table A-8-2 ammonia super heated........................................................................118

IV. List of figure

Figure2.1 solar cooling path......................................................................................14

G/HANNES T. And KINDALEM T. Page x

 DESIGN of SOLAR COOLING SYSTEM for AIR 2015
HANDLING UNITS of GARMENT ROOMS’ AC SYSTEM

Fig.2.2 the work flow and components of VARS......................................................18

Figure 2.3 process of vapour compression refrigeration system................................27
Figure 2.4 solar system cooling process....................................................................27
Figure3.1natural convection condenser.....................................................................40
Figure 3.2 capillary tube............................................................................................41
Figure 3.3 flat plate collectors...................................................................................48
Figure 3.4 parabolic dish collector............................................................................49
Figure 3.5 parabolic trough collectors.......................................................................51
Figure 4.1diagram of solar absorption refrigeration..................................................56
Figure 4.2 definitions of latitude, hour angle and solar declination...........................60
Figure 4.3declination angle of the sun.......................................................................60
Figure 4.4 day number recommended average day for each month...........................61
Figure 4.5 apparent daily path of the sun across the sky from sun rise to sun set......62
Figure 4.6 azimuth and altitude for northern latitude................................................64
Figure 5.1cross section of a parabolic trough with circular receiver.........................79
Figure 5.2 rim angle diagram....................................................................................81

CHAPTER-ONE

G/HANNES T. And KINDALEM T. Page xi

 DESIGN of SOLAR COOLING SYSTEM for AIR 2015
HANDLING UNITS of GARMENT ROOMS’ AC SYSTEM

Introduction

1. 1Back ground of the study

Cooling system an apparatus employed to keep the temperature of a structure or device
from exceeding limits imposed by needs of safety and efficiency. If overheated, the oil in a
mechanical transmission loses its lubricating capacity, while the fluid in a hydraulic
coupling or converter leaks under the pressure created. In an electric motor, overheating
causes deterioration of the insulation. The pistons in an overheated internal-combustion
engine may seize (stick) in the cylinders. Cooling systems are employed in automobiles,
industrial plant machinery, nuclear reactors, and many other types of machinery (For a
treatment of cooling systems used in buildings).

The cooling agents customarily employed are air and a liquid (usually water or a solution
of water and antifreeze), either alone or in combination. In some cases, direct contact with
ambient air (free convection) may be sufficient; in other cases, it may be necessary to
employ forced-air convection, created either by a fan or by the natural motion of the hot
body. Liquid is typically moved through a continuous loop in the cooling system by a pump.

Cooling is the process of removing heat from an area or a substance and is usually done by
an artificial means of lowering the temperature, such as the use of ice or mechanical
refrigeration.

In the olden days around 250 years B.C Indians, Egyptians etc. were producing ice by
keeping water in the porous pot open to cold atmosphere during the night period. The
evaporation of water in almost cool dry accompanied with irradiative heat transfer in the
clear night caused the formation of ice even the ambient temperature was above the freezing
temperature. Farther more, the East Indian were able to produce refrigeration by dissolving
salts in water as early as 4th century.

The use of evaporative cooling is another application used in the olden days. The cooling
of water in the earthen pots for drinking purpose is the most common example where
evaporation of water through the pores of the earthen pot is accompanied with cooling of
water. The aforesaid method of the production of cooling was feasible for commercial use
due to very small amount of ice production [26].

Commercial refrigeration and air conditioning account for over 17% of the nation’s energy
consumption in USA, there is a clear opportunity to increase the efficiency of refrigeration

G/HANNES T. And KINDALEM T. Page xii

 DESIGN of SOLAR COOLING SYSTEM for AIR 2015
HANDLING UNITS of GARMENT ROOMS’ AC SYSTEM

cycles. Today, most solar refrigeration devices on the market use absorption refrigeration to
achieve the cooling effect. These absorption devices are typically in the range of 30-40%
thermal efficiency and require massive heat transfer rates at high temperatures.

The use of vapour absorption refrigeration systems (VARS) in the solar thermal sector is a
new idea with minimal available research. Our team research is to design and analyse of a
single effect solar vapour absorption system dual piston compressor to implement in VAR.
We wanted to determine the thermodynamic efficiency of the system and the economic
feasibility of creating a VAR cycle using our generator, absorber and pump. Our motivation
was to create an economical refrigeration system using thermal vapour absorption instead of
the traditional mechanical or electrical vapour compression system. This system could be
used for air conditioning or refrigeration, so there is a large market for widespread use of
this sustainable system. Refrigeration and air condition [26].

1.2Problem statement

Without access and enough amount of energy many challenges are faced to communities of
developing countries. The unequal distribution of electricity supply in MAGARMENT as
well as between the urban and rural community was seen to be the main cause for non-
fulfilment of high demand of newer technological innovations in competition. There also
many circumstances where people do not have access to electricity or gusto power a
refrigeration system. For this reason, people are not able to store food as they would if they
had electricity. The need for cooling (refrigerating) for air handling unit of MAGARMENT
rooms, preserving food and other spoiling commodities like in villages is the main concern.
The use of household vapour compression refrigeration is limited due to lack of electricity
supply and unavailability of refrigerant without considerable side effect. In addition to this,
many of the vaccines used to control diseases require cold temperatures for preservation.
Without a reliable power infrastructure, developing countries often lack the resources for
keeping these vaccines cool in the long-term, hampering the ability to adequately protect
citizens.

1.3 Objective of the project

1.3.1 General objective

G/HANNES T. And KINDALEM T. Page xiii

 DESIGN of SOLAR COOLING SYSTEM for AIR 2015
HANDLING UNITS of GARMENT ROOMS’ AC SYSTEM

The general objective of this project is to design a solar cooling system (driven absorption
refrigerator) for air handling unit ofMagarment room’s of AC with cooling capacity
of411.93TR to be used not only in Magarment rooms but also in remote areas for which
after few developments is going to be a multipurpose refrigerator that is to be used for air
conditioning for good living condition, for preserving foods, for preserving vaccines
(medicines) and ice making for selling (commercial purpose).

The machine is supposed to be cost effective, robust or healthy so that it is going to be

accessible for everyone in need.
1.3.2 Specific objective of the project

To design an absorption refrigerator which is driven by solar energy uses air for condenser
cooling, equipped with solution pump and capable of reconditioning air in MAGARMENT
so as employers to work without confusing, to make the company profitable, additionally
preserving vaccines and related medicals which are used in rural health care centre or
clinics. It utilizes passive solar energy and can be built from available materials in nearby in
our country Ethiopia. Therefore, the specific objectives of our project are

 To provide comfortable condition not only for the labours that have done in
MAGARMENT rooms but also it provides better living process for people who have
lived in remote areas.
 To design and analyse solar thermal collector more detail and select the rest
components of solar absorption and refrigeration system in some way
 To have understanding installation of the project
 To increase operational life and provide continuous power supply
 In order to reduce greenhouse gas emission and pollution of the environment by
using solar vapour absorption refrigeration system
 To minimize maintenance and operational cost using solar vapour absorption
refrigeration system

1.4 Methodology
For this thesis the method that we used to design solar cooling system specially solar
absorption cooling system is;-

 Reading different literature review.

 Collecting and analyzing solar data from the information site.

G/HANNES T. And KINDALEM T. Page xiv

 DESIGN of SOLAR COOLING SYSTEM for AIR 2015
HANDLING UNITS of GARMENT ROOMS’ AC SYSTEM

For designing, the refrigeration system we have used:

 Text books
 Internet
 Soft copies and hard copies of different reviews
 Using interview method
 And etc.

The current design of the refrigerator is based on the weather of Mekelle, which could be
best for determining capacity and demand of target places of MAGARMENT Tixtile factory
for air conditioning handling units. Mekelle is located in Tigray, Ethiopia at an altitude of
13.40N and latitude of 150E.
1.5 Significance of the project

The study of this project has so many significances. Some of these advantages are:-

A) For us who deal with the design of the refrigerating machines. It helped us to know more
about how absorption cooling system (refrigerator) operates, working principle, how to
apply solar energy not only for air handling of MAGARMENT rooms AC system but
refrigeration and food preservation, recommended vaccine temperatures and what
refrigerants to use for such an application.
B) For those who want to deal with it will be a good guidance and good reference for
further research works.
C) It motivate us to have understanding what types of components we should use for
designing selecting and analysing of solar cooling system’s components (solar absorption
and refrigeration system’s components).
Energy is one of the current issues of the Country. In the remote area people use non-
renewable energy to facilitate daily activity. In order to improve this problem solar energy is
the most significance.
There is also a large energy demand in the Country and to full fill this demand the
government is working on different sources of energy. The result from the study explores
solar energy as a sustainable alternative for large scale air cooling, water heating and power
generation and it is a step forward to reduce dependency on imported oils.
The study benefits different industries in reducing the cost related to fuel and other high cost
energy sources. This in turn develops the energy alternatives for the industry as well as the

G/HANNES T. And KINDALEM T. Page xv

 DESIGN of SOLAR COOLING SYSTEM for AIR 2015
HANDLING UNITS of GARMENT ROOMS’ AC SYSTEM

Country. In addition, this research can be used as a reference for further study in the area for
researchers to do their project work
1.6 Scope of the project

The scope of this project work is limited to the design, the thermal solar collector only
because the department is unable to provide us with money for manufacturing and
developing the prototype nevertheless; this work includes the selection of the remaining
other components of the solar cooling system such as evaporator, generator, condenser,
expansion valve, solution pump and absorber in the circuit of the solar vapour refrigeration
cycle.

1.7 Expected outcome of the project

 The absorption refrigerator which is driven by solar energy uses air for condenser
cooling, equipped with solution pump and capable of cooling the air handling units
of MAGARMENT rooms, and it is possible up reserving vaccines and related
medicals which are used in rural health care centre or clinics is designed.
 Provided comfortable and better environmental conditions for the employers who
have done in garment houses
 The working principle of solar cooling system (solar absorption refrigeration system
is extended to understand not only for us but also for other academics- researchers.
 All components and parameters of solar absorption and refrigeration systems
without solar collector are selected, but solar collector is sized(designed) and
analysed.
 The operational life and continuous power supply are increased and provided
respectively.
 The greenhouse gas emission and pollution of the environment by using solar
vapour absorption refrigeration system is reduced.
 The maintenance and operational cost is minimized.

CHPTER-TWO

Literature review

G/HANNES T. And KINDALEM T. Page xvi

 DESIGN of SOLAR COOLING SYSTEM for AIR 2015
HANDLING UNITS of GARMENT ROOMS’ AC SYSTEM

2.1 Solar energy

Solar energy is one of the most available forms of\energy on the Earth’s surface, besides; it
is very promising and generous. The earth’s surface receives a daily solar dose of 10E plus 8
KW-hr, which is equivalent to 500 000 billion oil barrels that is one thousand times any oil
reserve known to man. The solar energy is collector area dependent, and is a diluted form of
energy and is available for only a fraction of the day. Also, its availability depends on
several factors such as latitude and sky clearness suggested by Duffie& Beckman in 1980
[2].

At the same time, its system requires high initial cost. But on the other hand, it has some
attractive features such as its system requiring minimum maintenance and operation cost,
and it does not have negative effects on the environment. Important feature of solar energy
is its ability to satisfy rural areas where conventional energy systems might be not suitable
or uneconomical. Solar energy is being invested in many forms. The first form is the most
familiar and that is using it for supplying domestic hot water for residences which is the
most worldwide spread form of solar energy use. Another form is the photovoltaic, and
these are special cells that transfer solar energy to electric ones. Also, some power plants are
now present that produce electricity from solar energy (e.g. US Pilot Power Plant of 516
degree Celsius average temperature and the Japanese experiment stations of 1MW power
output. Some other applications of solar energy being investigated are its use for cooling
and heating of buildings. A lot of research is being conducted for this purpose especially in
countries where there is high availability of solar energy just like in India. Solar energy is
abundant in summer months where there is no heating load, but instead cooling is required.
Solar air-conditioning has the advantage of both the supply of the sunshine and the need for
refrigeration reaching maximum levels in the same season. As a result, solar air-
conditioning is the particularly attractive application for solar energy.

2.1.1 Devices for solar thermal collections

In order to evaluate the potential of solar energy for the different solar cooling systems, a
classification has been made by the scientists Best and Orgetain1998. It is based on the two
main concepts – solar thermal technologies for the conversion of solar heat into hot water,
and the solar cooling technologies for the cold production.

 Flat plate collectors

G/HANNES T. And KINDALEM T. Page xvii

 DESIGN of SOLAR COOLING SYSTEM for AIR 2015
HANDLING UNITS of GARMENT ROOMS’ AC SYSTEM

 Dish type concentrating collectors

 Linear focusing concentrators (parabolic trough collector)
 Photovoltaic

2.1.2 Application of solar energy in cooling system

a) Refrigeration and air conditioning

A very promising application is refrigeration. Refrigeration encompasses household
refrigerators, space cooling air conditioning of buildings etc. but the best concentrate
attention on one particular possible device, a machine for making ice. This is for several
reasons, both technological and socio-economic. For one thing, converting the solar
radiation into ice solves the problems of intermittency and storage. Ice can be stored for
months. In addition, it is transportable. An ammonia-water cycle is contemplated. Several
icemakers and refrigerators using this cycle and solar energy input have been built [12].
b) Solar Drying
The use of solar energy for crop drying was known to have a long history as in case of farm
harvest drying in plough fields (farm lands) but in case of fruit drying such as
tomatoes and bananas (fruits with high moisture content) is still at grass root level. For our
country Ethiopia, the researches on solar dryers are preceding good to be used at both green
houses and home.
There are two known types of driers. These are:
 The natural convection dryers work based on the principle that the air
density difference causes pressure differences so that the hot air at the
collector side is pushed away and replaced by the cold moisturized or
ambient air.
 The forced convection dryers use fan as a means for creating pressure
difference between the hot and cold air so that increase the overall efficiency
of the system.
c) Solar cooking
Cooking is an activity that must be carried out almost on a daily basis for the sustenance of
life. An enormous amount of energy is then expended regularly on cooking; cooking may
be classified in four major categories based on the required range of temperature. These
are:-
1. Baking 85-90 ℃
2. Boiling 100-130℃

G/HANNES T. And KINDALEM T. Page xviii

 DESIGN of SOLAR COOLING SYSTEM for AIR 2015
HANDLING UNITS of GARMENT ROOMS’ AC SYSTEM

3. Frying 200-250 ℃
4. Roasting 300℃
Solar cooking offers an effective method for utilizing solar energy for meeting a
considerable demand for cooking energy and hence protecting the environment i.e. it is
pollution free, efficient and in exhaustible. The followings are some commonly used solar
cookers.
 Box type solar cookers
 Concentrating solar cookers
 Parabolic solar cookers
 Panel type solar cookers
d) Solar water distillation and heaters
Applying solar energy for water purification or distillation water heating for showering
and cleaning purposes is based on the principle that a heat transfer fluid will get heated
using solar energy and this heat is used to boil water to some required temperature for
separating from residues (in case of distillation) and for Warming(in case of heating) [28].
2.1.2 Instrument for measuring solar radiation

The major problem in measuring solar radiation is not only the choice of an acceptable
reference scale but also materialization of the absolute scale by asset of basic absolute
radiometers. Absolute measurement refers measured quantity by means of unique laws of
physics and constants of physics directly to the fundamental units of LTM system obtained
by the use of absolute instruments.

Table 2.1 general characteristics of methods for radiant energy measurement

Effect used Wave length Sensitivity Linearity Selectivity
Calorimetric All wave Low Very good Absent
Length
Thermoelectric 5 Good Good Absent
Photoelectric 2 High Poor High
Photographic 1.2 High Bad High
Visual 0.4−o .75 High Bad High

2.1.3Types of instrument

The instruments which are used for measuring different radiation parameters are:-

2.1.3.1.Pyrheliometer: -an instrument for the measurement of the global solar radiation
received from the entire hemisphere when fitted with a shading ring. It measures the diffuse

G/HANNES T. And KINDALEM T. Page xix

 DESIGN of SOLAR COOLING SYSTEM for AIR 2015
HANDLING UNITS of GARMENT ROOMS’ AC SYSTEM

radiation and when mounted with its sensor facing dawn wards. It measures reflected solar
radiation which when expressed a function of global radiation. It is consists of a black
surface which heats up when exposed to solar radiation. Its temperature increases until the
rate of heat gain by solar radiation equals the rate of heat lose by convection, conduction and
radiation.
2.1.3.2Pyranometer: - is an instrument measuring for an intensity of direct solar radiation at
normal incident. In contrast to pyrheliometer, the black observer plat with hot junction of
thermopile attached to it is located at the base of the tube.
2.1.3.3Pyrheliometer: -an instrument for the measurement of the net flux of long-wave
radiation through a horizontal surface during the night.
2.1.3.4Pyradiometer: -an instrument for the measurement of the net flux of dawn wards and
upward total radiation (short-wave &long-wave radiation) through horizontal surface.
Commercially available pyranometers primarily have thermopile, silicon cell or bimetallic
strip sensors. Thermopiles are calorimetric sensors. Silicon cells are quantum detectors and
bimetallic strips are calorimetric sensors that depend upon the thermal expansion of metals
[3,5].
Types of pyrheliometer

To measure solar radiations there are a number of instruments that are used for measuring
solar radiations in which grouped under the pyrheliomers. These are:

Abbot silver disc pyrheliometer: -this instrument was designed by abbot in 1902at
Smithsonian institute and was used as secondary standard for radiation measurement. The
sensitive element is a blackened sliver disc in which its diameter is being 3.8cmand 0.7cm
thickness. The disc has a hole, bored radially into its edge in to which is inserted the bulb of
a sensitive mercury in glass thermometer. A thermal contact between silver disc and
thermometer bulb is maintained by using mercury.

Linke-Fussnerpyrheliometer (actinometer):- is one of the most convenient instruments that

are used for the measurement of direct (beam) radiation at normal incident with or without
filters. It is designed in1913 by Like-Fussner. The main body of this instrument composed
of six massive copper ring which are contoured on the inside of the tube to produce a set of
radiation diaphragms for decreasing internal reflections for defining the acceptance angle of
the instrument and liking turbulent air current inside the instrument thus securing a stability
and good sensitivity.

G/HANNES T. And KINDALEM T. Page xx

 DESIGN of SOLAR COOLING SYSTEM for AIR 2015
HANDLING UNITS of GARMENT ROOMS’ AC SYSTEM

Eppley normal incident pyrheliometr (NI):-NI has found a wide acceptance in many parts
of the world. It is designed by Eppley in1923. The latest model of NI pyrheliometer uses a
thin silver disc with 9mm in diameter as receiver which is coated with parson optical black
lacquer.

Moll-gorezynski:-pyranometer this instrument is designed by doctor W.J moll of university

of Utrecht in 1924.

Photovoltaic silicon pyranometer:- invented in 1954 at bell laboratory which is being

available a new and power full transducers capable of producing the electrical signal which
is proportional to the intensity of the solar radiation. These solar cells can be used for the
measurement of global and diffuse radiation.

2. 2Solar cooling system

The solar cooling technologies are mainly classified into two main groups depending on the
energy supply. These are: - a thermal/work driven system and electricity (Photovoltaic)
driven system. Each group can be classified as the following:

2.2. 1Thermal (work driven system)

 Absorption refrigeration cycle
 Adsorption refrigeration cycle
 Chemical reaction refrigeration cycle
 Desiccant cooling cycle
 Ejector refrigeration cycle

2.2.2 Electricity (Photovoltaic) driven system

Photovoltaic power systems are generally classified according to their functional and
operational requirements, their component configuration, and how the equipment is
connected to other power sources and electrical loads. The two principal are grid connected
or utility interactive system and standalone system.

As (Wincher ,1997) explained that stand alone PV systems are designed to operate
independent of the electric utility grid and are generally designed and sized to supply certain
DC and/or AC electrical loads. These types of system may be powered by a PV array only,
or may use wind, an engine generator or utility power as an auxiliary power source what is
called a PV hybrid system. The type of standalone PV system is direct coupled system

G/HANNES T. And KINDALEM T. Page xxi

 DESIGN of SOLAR COOLING SYSTEM for AIR 2015
HANDLING UNITS of GARMENT ROOMS’ AC SYSTEM

where the DC output of PV module or array is directly connected to a DC load since is no

electrical storage device, like battery in direct coupled systems, the load only operates
during sun light hours. The following are some classifications of PV system.
 Vapour compression refrigeration cycle
 Thermo-electric refrigeration cycle
 Stirling refrigeration cycle

The solar-powered cooling system generally comprises three main parts:

 The solar energy conversion equipment,

 the refrigeration system,
 The cooled object (e.g. a cooling box).

A number of possible “paths” from solar energy to the “cooling services” are shown in
Figure 1.

Figure 2.1: Solar cooling path

In Figure1above, the absorption system appears to be one of the most promising methods.
The absorption cycle is similar in certain respects to the electrically driven vapour
compression machines. A refrigeration cycle is operated with the condenser, expansion
valve, and evaporator if low-pressure vapour from the evaporator can be transformed into

G/HANNES T. And KINDALEM T. Page xxii

 DESIGN of SOLAR COOLING SYSTEM for AIR 2015
HANDLING UNITS of GARMENT ROOMS’ AC SYSTEM

high-pressure vapour rand delivered to the condenser. The vapour compression system uses
a compressor for this task. The absorption system first absorbs the low pressure vapour in an
appropriate absorbing liquid. Of Embodied in the absorption process is the conversion of
vapour into liquid, and since the most industrial processes use a lot of thermal energy by
burning fossil fuel to produce steam or heat for the purpose. After the processes, heat is
rejected to the surrounding as waste. This waste heat can be converted to useful refrigeration
by using a heat operated refrigeration system, such as an absorption refrigeration cycle.
Electricity purchased from utility companies for conventional vapour compression
refrigerators can be reduced. The use of heat operated refrigeration systems help reduces
problems related to global environment, such as the so called greenhouse effect from CO2
emission from the combustion of fossil fuels in utility power plants. Another difference
between absorption systems and conventional vapour compression systems is the working
fluid used. Most vapour compression systems commonly use chlorofluorocarbon
refrigerants (CFCs), because of their thermo physical properties. It is through the restricted
use of CFCs; due to depletion of the ozone layer that will make absorption systems more
prominent. However, although absorption systems seem to provide many advantages,
vapour compression systems still dominate all market sectors. In order to promote the use of
absorption systems, further development is required to improve their performance and
reduce cost. As an alternative to heat generated from power plants solar energy can be used
in urbanized community. However, for rural communities in developing countries it is the
best source of energy. There are several important reasons for considering solar energy as an
energy resource to meet the needs of developing countries.

 First, most of the countries called developing are in or adjacent to the tropics and
have good solar radiation available.
 Secondly, energy is a critical need of these countries but they do not have widely
distributed readily available supplies of conventional energy resources.
 Thirdly, most of the developing countries are characterized by arid climates,
dispersed and inaccessible populations and a lack of investment capital and are thus
faced with practically insuperable obstacles to the provision of energy by
conventional means, for example, by electrification. In contrast to this solar energy
is readily available and is already distributed to the potential users.
 Fourthly, because of the diffuse nature of solar energy the developments all over the
world have been in smaller units, which fit well into the pattern of rural economics.

G/HANNES T. And KINDALEM T. Page xxiii

 DESIGN of SOLAR COOLING SYSTEM for AIR 2015
HANDLING UNITS of GARMENT ROOMS’ AC SYSTEM

Solar cooling technologies are broadly characterized as either passive or active depending
on the way they capture, convert and distribute sunlight.

2.2.3 Active solar cooling technique: - use photovoltaic panels, pumps, and fans to
convert sunlight into useful outputs. Active solar technologies increase the supply of energy
and are considered supply side technologies.

2.2.4 Passive solar cooling techniques: - technologies reduce the need for alternate
resources and are generally considered demand side technologies. Passive solar techniques
include selecting materials with favourable thermal properties, designing spaces that
naturally circulate air, and referencing the position of a building to the Sun

The applications of solar energy which successful today are

(1) Heating and cooling of residential building.

(2) Solar water heating

(3) Solar drying of agricultural and animal products

(4) Solar distillation on a small community scale.

(5) Salt production by evaporation of seawater or inland brines.

(6) Solar cookers

(7) Solar engines for water pumping

(8)Food refrigeration

(9) Bio conversion and wind energy which are indirect source of solar energy

(10) Solar furnaces

(11) Solar electric power generation

Also solar energy operated air conditioners and refrigerators are now widely used and are of
two types. These are:

2.2.5 Intermittent cooling type

Cooling produced discontinuously is known as intermittent cooling (intermittent
refrigeration) is simpler in operation, portable that is why, such an intermittent cooling are

G/HANNES T. And KINDALEM T. Page xxiv

 DESIGN of SOLAR COOLING SYSTEM for AIR 2015
HANDLING UNITS of GARMENT ROOMS’ AC SYSTEM

most suitable. In this cooling process, there are two separator operations; these are re-
generation and re-cooling taking place at different times. Here, generator and absorber units
are combined and refrigerant/rich absorbent solution is heated which formed rich refrigerant
vapour and condensed stored in condenser/evaporator units [8].
2.2.6 Continuous cooling type
The cooling process produced continuously is also known as continuous absorption cooling
(refrigeration) process. For most application, continuous cooling is required such as cooling
of building where energy source would be solar collector storage auxiliary heat system. This
system is more reliable where refrigeration and regeneration takes place simultaneously
producing a continuous cooling effect [8].
2.2.7Solar vapours absorption cooling (refrigeration) system

An absorption-generation process replaces the compressor. Now, instead of compressing a

vapour between the evaporator and the condenser as in a vapour compression refrigeration
cycle, the refrigerant is absorbed by a secondary substance, called an absorbent, to form a
liquid solution. The liquid solution is then pumped to the higher pressure. The early
development of an absorption cycle dates back to the 1700’s. It was known that ice could be
produced by an evaporation of pure water from a vessel contained within an evacuated
container in the presence of sulphuric acid. In1810, ice could be made from water in a
vessel, which was connected to another vessel containing sulphuric acid. As the acid
absorbed water vapour, causing a reduction of temperature, layers of ice were formed on the
water surface. The major problems of this system were corrosion and leakage of air into the
vacuum vessel. In 1859, Ferdin and Carrie introduced a novel machine using
water/ammonia as the working fluid. This machine took out a US patent in 1860. Machines
based on this patent were used to make ice and store food. It was used as a basic design in
the early age of refrigeration development. Cess is akin to condensation, heat must be
rejected during the process. In the 1950’s, a system using lithium bromide/water as the
working fluid was introduced for industrial applications. A few years later, double-effect
absorption system was introduced and has been used for a high performance heat [28].

G/HANNES T. And KINDALEM T. Page xxv

 DESIGN of SOLAR COOLING SYSTEM for AIR 2015
HANDLING UNITS of GARMENT ROOMS’ AC SYSTEM

Fig.2.2 the work flow and components of VARS

To reach at the status of the refrigeration technology so many studies and researches has
been done. These studies come up with different working fluid pairs and cycles. Each of
them has their positive side and limitations. Some of the well-known studies and researches
are compiled in literature review documents. In case of solar absorption refrigeration,
although so many reviews were found, some of them are listed below.
A) Single-effect absorption system
Single effect absorption refrigeration system is the simplest and most commonly used
design. There are two design configurations depending on the working fluids used. High
temperature heat supplied to the generator is used to evaporate refrigerant out from the
solution (rejected out to the surroundings at the condenser) and is used to heat the
solution from the absorber temperature (rejected out to the surroundings at the
absorber).Thus, irreversibility is caused as high temperature heat at the generator is wasted
out at the absorber and the condenser. In order to reduce this irreversibility, a solution heat
exchange is introduced The heat exchanger allows the solution from the absorber to be
preheated before entering the generator by using the heat from the hot solution leaving the

G/HANNES T. And KINDALEM T. Page xxvi

 DESIGN of SOLAR COOLING SYSTEM for AIR 2015
HANDLING UNITS of GARMENT ROOMS’ AC SYSTEM

generator. Therefore, the COP is improved as the heat input at the generator is reduced.
When volatility absorbent such as water/NH3 is used, the system requires an extra
component called “a rectifier”, which will purify the refrigerant before entering into the
condenser.
B) Absorption heat transformer
This system uses heat from an intermediate temperature reservoir as the driving heat
(normally from industrial waste heat).The system rejects heat out at a low temperature level
(normally to the surroundings).The useful output is obtained at the highest temperature level.
The use of an absorption heat transformer allows any waste heat to be upgraded to a higher
temperature level without any other heat input except some work required circulating the
working fluid. This cycle has similar components as a single effect absorption cycle. The
difference is that an expansion device installed between the condenser and the evaporator is
substituted by a pump.
C) Multi-effect absorption refrigeration cycle
Double-effect absorption refrigeration cycle was introduced during 1956 and 1958. High
temperature heat from an external source supplies to the first-effect generator. The
vapour refrigerant generated is condensed at high pressure in the second-effect
generator. The heat rejected is used to produce addition refrigerant vapour from the solution
coming from the first effect generator. This system configuration is considered as a series-
flow-double-effect absorption system.
A double-effect absorption system is considered as a combination of two single effect
absorption systems whose COP value is COP single. Several types of multi-effect
absorption cycle have been analysed such as the triple effect absorption cycle and the
quadruple-effect absorption cycle. However, an improvement of COP is not directly linked
to the increment of number of effect. It must be noted that, when the number of effects
increase, COP of each effect will not be as high as that for a single-effect system. Moreover,
the higher number of effect leads to more system complexity. Therefore, the double-effect
cycle is the one that is available commercially.
D) Absorption refrigeration cycle with GAX
GAX represented for generator/absorber heat exchanger or sometimes is also called DAHX,
which stands for disrober/absorber heat exchanger. Higher performance can be achieved
with a single-effect absorption system. Referring to the parallel-flow-double effect
absorption system mentioned earlier, the system consists of two single-effect cycles working
in a parallel manner. The concept of GAX is to simplify this two stage- double-effect

G/HANNES T. And KINDALEM T. Page xxvii

 DESIGN of SOLAR COOLING SYSTEM for AIR 2015
HANDLING UNITS of GARMENT ROOMS’ AC SYSTEM

absorption cycle but still produce the same performance. The idea of GAX was introduced
in 1911by Altenkirch and Tenckhoff. An absorber and a generator may be considered as a
counter-flow-heat exchanger at the absorber,
Weak-refrigerant solution from the generator and vapour refrigerant from the evaporator
enter at the top section. Heat produced during the absorption process must be rejected
out in order to maintain ability to absorb the refrigerant vapour.
E) Absorption refrigeration cycle with an absorber-heat-recovery
The use of a solution heat exchanger improves the system coefficient of performance
(COP). Rich-refrigerant solution from the absorber can be preheated before entering the
generator by transferring heat from hot solution coming from the generator. By introducing
an absorber-heat-recovery, temperature of the rich refrigerant solution can be further
increased. Similar to the GAX system, the absorber is divided into two sections. Heat is
rejected out at a different temperature. The lower temperature section rejects heat out to the
surroundings as usual. This system was studied theoretically by using various working
fluids; water/NH3 and LiNO3/NH3. The cycle with an absorber-heat-recovery was found to
have 10% improvement in coefficient of performance (COP).
F) Half-effect absorption refrigeration cycle
It must be noted that, any absorption refrigeration system can be operated only when the
solution in the absorber is richer in refrigerant than that in the generator. When the
temperature increases or the pressure reduces, the fraction of refrigerant contained in the
solution is reduced, and vice versa. When the generator temperature is dropped, the solution
circulation rate will be increased causing the COP to drop. If it is too low, the system can be
no longer operated. The half-effect absorption system was introduced for an application
with a relatively low-temperature heat source. The system configuration is the same as the
double-effect absorption system using water/NH3except the heat flow directions are
different. High temperature heat from an external source transfers to both generators. Both
absorbers reject heat out to the surroundings.
G) Combined vapour absorption-compression cycle
This system is usually known as an absorption-compression system.
The condenser and the evaporator of a conventional vapour-compression system are
replaced with a restorer (vapour absorber) and a desorbed (vapour generator). For given
surrounding temperature and refrigerating temperature, the pressure differential across the
compressor is much lower than a conventional vapour-compression system. Thus, the COP
is expected to be better than a conventional vapour compression system. Altenkirch did the

G/HANNES T. And KINDALEM T. Page xxviii

 DESIGN of SOLAR COOLING SYSTEM for AIR 2015
HANDLING UNITS of GARMENT ROOMS’ AC SYSTEM

first investigation in 1950 and proposed a potential for energy saving. The cycle can
be configured as a heat pump cycle. The first experimental results of an
absorption/compression cycle with direct desorbed/ absorber heat exchanger was presented
by Groll and Radermacher. A combined cycle proposed by Caccoilaet al. employing two
combinations of working Fluids i.e. refrigerant (NH3)/ absorbent (H2O) and H2O/KHO. The
rectifier is absent and also the highest-pressure is decrease.
This is a modified plant from a two stage-solution circuit proposed by Raneand
Radermacher.
H) Sorption-desorption cycle
Altenkirch introduced the idea of a sorption-desorption cycle in 1913. The cycle employs
two solution circuits instead of only one. The condenser and evaporator section of a
conventional single-effect absorption system is replaced with are sorted and adsorbed
respectively. This Provides more flexibility in the cycle design and operations. The solution
loops concentrations can be varied allowing adjustment of the component temperatures
and pressures to the application requirement. can be varied allowing adjustment of the
component temperatures and pressures to the application requirement.
I) Dual-cycle absorption refrigeration
The concept of a dual-cycle absorption system is similar to a parallel-double-effect
absorption system. However, this system consists of two completely separated cycles using
different kinds of working fluid. Hanna et al. invented a dual-cycle absorption refrigeration
and heat pump. This system consists of two single-effect absorption cycles using water/NH3
and LiBr/water. The
NH3 system is driven by heat obtained from an external heat source. The heat reject from its
absorber and condenser is used as a driving heat for the LiBr/water system. The LiBr/water
system rejects heat out to the surrounding at the condenser and the absorber as
usual. The cooling effect can be obtained from both evaporators.
J) Combined ejector-absorption refrigeration cycle
An ejector can be used to improve performance of absorption refrigeration system. One
notable approach was devised by Kuhlenschmidt. The aim is to develop an absorption
system using working fluid based on salt absorbent, capable of operating at low evaporator
temperatures and employing an air-cooled absorber. This system employs two-stage
generators similar to that used in a double effect absorption system. However, in contrast
to a conventional double-effect absorption system, the low-pressure vapour refrigerant
from the second-effect generator is used as a motive fluid for the ejector that entrains

G/HANNES T. And KINDALEM T. Page xxix

 DESIGN of SOLAR COOLING SYSTEM for AIR 2015
HANDLING UNITS of GARMENT ROOMS’ AC SYSTEM

vapour refrigerant from the evaporator. The ejector exhaust is discharged to the absorber,
causing the absorber pressure to be at a level higher than that in the evaporator.
K) Osmotic-membrane absorption cycle

This system was proposed by Zerweck in1899. The system consists of a condenser and an
evaporator as usual. Rich-refrigerant solution in the absorber and weak-refrigerant solution
in the generator are separated from each other by using an osmotic membrane. The osmotic
membrane allows only the refrigerant to pass. Thus, the refrigerant from the absorber can be
transferred to the generator by an osmotic diffusion effect through the membrane without
any mechanical pump.
L) Self-circulation absorption system using LiBr/water
Even if the prime energy for an absorption refrigeration system is in the form of
heat, some electricity still required to drive a circulation pump. Some absorption
refrigeration systems do not require any circulation pump. In such a system, working fluid
is circulated naturally by a bubble pump.
Yazaki Inc. Of Japan introduced a self-circulate absorption refrigeration system based on a
single-effect system using LiBr/water. Using water as a refrigerant, differential pressure
between the condenser and the evaporator is very low and can be maintained by using the
principle of hydrostatic-head. The solution from the absorber can be circulated to the
generator by a bubble pump. The weak-refrigerant solution returns gravitationally back to
absorber. With the effect of the bubble pump, the solution is boiled and pumped at the same
time. Smith and Khahra carried out a study of performance of CH- 900-B Yazaki absorption
water chillier operated using propane gas. Eriksson and Jernqvist developed a 10 kW self-
circulation absorption heat transformer using NaOH/water (sodium hydroxide/water).

M) Diffusion absorption refrigeration system (DAR)

DAR is another type of self-circulate absorption system using water/NH 3. As NH3 is the
working fluid, differential pressure between the condenser and the evaporator is too large to
be overcome by a bubble-pump. The concept of DAR was proposed by Platen and
Munters students at the Royal Institute of Technology, Stockholm. An auxiliary gas is
charged to the evaporator and the absorber. Therefore, no pressure differential in this
system and the bubble-pump can be used. The cooling effect is obtained based on the
principle of partial pressure. Because the auxiliary gas is charged into the evaporator and the
absorber, the partial pressure of ammonia (NH 3) in both evaporator and absorber is kept low

G/HANNES T. And KINDALEM T. Page xxx

 DESIGN of SOLAR COOLING SYSTEM for AIR 2015
HANDLING UNITS of GARMENT ROOMS’ AC SYSTEM

enough to correspond with the temperature required inside the evaporator. The auxiliary gas
should be non-condensable such as hydrogen or helium which is used as control system.
The working fluid in an absorption refrigeration system is a binary solution
consisting of refrigerant and absorbent. The left side or refrigerating components
(condenser, expansion valve and evaporator) contain liquid refrigerant while the right
side or regeneration components (absorber, generator and solution pump) contains
liquid refrigerant contain a binary solution of absorbent/refrigerant. In following diagram
the solution in the left side will absorb refrigerant vapour from the right side causing
pressure to reduce. While the refrigerant vapour is being absorbed, the temperature of the
remaining refrigerant will reduce because of its vaporization. This causes refrigeration
effect to occur inside the right side component i.e. the evaporator. At the same time,
solution inside the right side becomes more dilute because of the higher content of
refrigerant absorbed. This is called the “absorption process”. Normally, the absorption
process is an exothermic process. Therefore, it must reject heat out to the surrounding in
order to maintain its absorption capability.
Whenever the solution cannot continue with the absorption process because of saturation of
the refrigerant, the refrigerant must be separated out from the diluted solution. Heat is
normally the key for this separation process. It is applied to the right side on the absorber in
order to dry the refrigerant from the solution. The refrigerant vapour will be condensed by
transferring heat to the surroundings. With these processes, the refrigeration effect can
be produced by using heat energy.
However, the cooling effect cannot be produced continuously, as the process cannot be
done simultaneously. Therefore, an absorption refrigeration cycle is a combination of these
two processes. As the separation process occurs at a higher pressure than the absorption
process, a pump (solution pump or bubble pump) is required to circulate the solution. The
work input for the pump is negligible relative to the heat input at the generator. Therefore,
the pump work is often neglected for the purposes of analysis.

2.2.7.1 Components of solar absorption and refrigeration system

The main components of solar cooling system (solar absorption and refrigeration system)
are:-
o Generator (located on high pressure side).
o Condenser (located on high pressure side).
o Expansion valve (throttling valve or metering device)

G/HANNES T. And KINDALEM T. Page xxxi

 DESIGN of SOLAR COOLING SYSTEM for AIR 2015
HANDLING UNITS of GARMENT ROOMS’ AC SYSTEM

o Heat exchanger
o Absorber (located on low pressure side)
o Evaporator (located on low pressure side)
o Solution pump
o Solar collector
o Rectifier

2.2.7.2 Working principle SARS

A Simple operated solar absorption refrigeration system is first H 2O heated in solar collector
array is passed through a heat exchanger (generator) where it transferred heat to a solution
mixture of the absorbent &refrigerant, which is rich in refrigerant. Refrigerant vapour is
boiled off at high pressure& temperature and goes to the condenser where it condensed in to a
high pressure liquid. The high pressure liquid is throttled to allow pressure and temperature in
an expansion valve& passes through the evaporator coil. Here, the refrigerant absorbed heat in
the absorber and cooling is therefore, obtained in the space [12].

2.2.7.3 Phase of absorption cooling cycle

The cooling can be described in three phases. These are:

1. Evaporation: Liquid refrigerant evaporates in a low partial pressure environment,
thus extracting heat from the surrounding (e.g. from the refrigeration system. Due to
the low pressure, the low temperature needed for evaporation is lower.
2. Absorption: the new gaseous refrigerant is absorbed by another liquid like (e.g. salt
solution) reducing its partial pressure in the evaporator and allowing more
refrigerant to evaporate.
3. Regeneration: The refrigerant saturated liquid is heated, causing vapour.

2.2.8 Compression refrigeration system

This system is also referred to as mechanical refrigeration or electrical refrigeration “either

which works mechanically or electrical system. Dry saturated working fluid (refrigerant) is
compressed isentropic ally or in a reversible adiabatic to the condenser pressure at the
compressor. Since the refrigerant undergoes a change of phase during the cyclic process, it
is said to be a phase change cycle. The refrigerant is then condensed in a heat exchanger
giving saturated liquid. Then isentropic expansion takes place in order for bringing the

G/HANNES T. And KINDALEM T. Page xxxii

 DESIGN of SOLAR COOLING SYSTEM for AIR 2015
HANDLING UNITS of GARMENT ROOMS’ AC SYSTEM

temperature and pressure of the refrigerant to evaporator pressure and temperature. At the
evaporator, it evaporates by giving the refrigerating effect of the required item. After
evaporation, it enters the compressor again thus completing the cycle. The vapour-
compression–refrigeration in which refrigerant under goes phase changes, is one of the
many refrigeration cycles and is the most widely used method for air conditioning of
buildings and automobile. It is also used in domestic and commercial refrigerator, large
scale warehouses for frozen storage of food& meats, refrigerated truck and railroad cars, and
host of other commercial and industrial services. The compression refrigerant cycle uses a
circulating liquid refrigerant as the medium which absorbs and removes heat from the space
to be cooled and subsequently rejects [3].

Components of vapour compression refrigeration system are:-

 Compressor
 Condenser
 Evaporator
 Thermal expansion valve (throttling valve or metering device)
 Fan used for sucking warm air from the surrounding to the condenser refrigerant
to evaporate out. This happens at significantly higher pressure at which the
refrigerant is then condensed through a heat exchanger to replenish the supply
of liquid refrigerant in the evaporator.

Figure 2.3 process of vapour compression refrigeration system

G/HANNES T. And KINDALEM T. Page xxxiii

 DESIGN of SOLAR COOLING SYSTEM for AIR 2015
HANDLING UNITS of GARMENT ROOMS’ AC SYSTEM

Figure 2.4 solar system cooling process

Table 2.2comparison s between vapor absorption system (VAR) and vapor

compression system(VCR)
VAR VCR
Operation operated on thermal energy which is Operated on mechanical or electrical energy
cheaper than mechanical and which is expensive in its cost (operated on
electrical energy(operated on heat) work)
Moving the only moving parts in VAP is a A No of moving parts such a compressor is a
Parts pump quite small in size than one in which its size quite larger than size of
compressor pump, its cost is therefore high
Noise less noise is formed High noise is formed
Vibration less or no Vibration formed High vibration is formed
Vapor TO heating the generator is Degree of super heated is governed by suction
Quality of slightly super-heated& is controlled state of vapor. In practice TO of leaving
refrigerant heat exchanger provided after Generator is 340k (67℃ ) against about420k
generator (147℃ ) in case of compression system. VAR
requires smaller condenser than VCR.

capacity of absorption is controlled Capacity of compression system decreases

Vapor- by adjusting the steam or generator rapidly with reduced evaporator pressure
pressure TO even if evaporator TO falls
The cop of VAR is usually much The cop of VCR is usually much higher in
COP lower in magnitude, but the low value magnitude
of former is not much important since
it uses waste energy
Maintenanc since the only moving parts are Regular maintenance is required

G/HANNES T. And KINDALEM T. Page xxxiv

 DESIGN of SOLAR COOLING SYSTEM for AIR 2015
HANDLING UNITS of GARMENT ROOMS’ AC SYSTEM

e pumping equipments its maintenance

is much less than VCR
Waste of- less waste of refrigerant High waste of refrigerant
Refrigerant
Space small units of absorption system is Large units of compression system is rather
rather bulky than large units of bulky than small units of VCR system
absorption system

[Source of Manohar Prasad, refrigeration and air conditioning text book, second edition
2003, 3]
Vapour Absorption system is an attractive method for utilizing low grade energy directly for
cooling. This is an important advantage as against the conventional vapour compression
system which operates on high grade energy. Another important feature of this system is
that it does not use any moving component, except a very small liquid pump [28].

2.3 Working fluid for absorption refrigeration systems

A survey of absorption fluids provided by Marcriss suggests that, there are some 40
refrigerant compounds and 200 absorbent compounds available. The most common working
fluids are Water/NH3 and LiBr/water.

Since the invention of an absorption refrigeration system, water/NH3 has been widely used
for both cooling and heating purposes. Both NH3 (refrigerant) and water (absorbent) are
highly stable for a wide range of operating temperature and pressure. NH 3 has a high latent
heat of vaporization, which is necessary for efficient performance of the system. It can be
used for low temperature applications, as the freezing point of NH 3 is -770C. Since both NH3
and water are volatile, the cycle requires a rectifier to strip away water that normally
evaporates with NH3. Without a rectifier, the water would accumulate in the evaporator and
offset the system performance. Disadvantages include its high pressure, toxicity, and
corrosive action to copper and copper alloy. However, water/NH3 is environmental friendly
and of low cost.
The use of LiBr/water for absorption refrigeration systems began around 1930. Two
outstanding features of LiBr /water are non-volatility absorbent of LiBr (the need of a
rectifier is eliminated) and extremely high heat of vaporization of water (refrigerant).

G/HANNES T. And KINDALEM T. Page xxxv

 DESIGN of SOLAR COOLING SYSTEM for AIR 2015
HANDLING UNITS of GARMENT ROOMS’ AC SYSTEM

However, using water as a refrigerant limits the low temperature application to that above
00C. As water is the refrigerant, the system must be operated under vacuum conditions. At
high concentrations, the solution is prone to crystallization. It is also corrosive to some
metal and expensive.
Although LiBr/water and water/NH3 have been widely used for many years and their
properties are well known, R22 and R21 have been widely suggested because of their
favourable solubility with number of organic solvents.
Performance of absorption refrigeration systems is critically (or fundamentally) dependent
on the chemical and thermodynamic properties of the working fluid mixture [26, 3].
The main properties of working fluids are listed as follow.
2.4 Properties of absorbent &refrigerant solution

2.4.1 Properties of refrigerants:

 Should be nontoxic
 High solubility with refrigerant.
 Remain in liquid form
 The positive vapour of refrigerant permits a boiling points at 2℃ to -45℃&
condensation at 40℃
 High enthalpy of vaporization
 Low specific heat
 Low molecular weight
 High affinity for absorbent at low TO and low affinity at high TO
 should have high Chemical stability,
 should be non-corrosive

2.4.2 Properties of absorbents:

In order to get good performance of solar absorption refrigeration system the following
characteristics are desirable.

 High boiling point

 Low viscosity
 Low specific heat
 Should have Chemical stability
 Should be non-toxic

G/HANNES T. And KINDALEM T. Page xxxvi

 DESIGN of SOLAR COOLING SYSTEM for AIR 2015
HANDLING UNITS of GARMENT ROOMS’ AC SYSTEM

2.4.3 for absorbent refrigerant combination

In order get good performance of solar absorption refrigeration system the following
characteristics are desirable:

 It should have high degree of negative deviation from Rout’s law

 The mixture should have low specific heat and low viscosity
 They should give noncorrosive mixture
 They should yield a solution with as small heat of dilution as is compatible with
other properties
 The elevation of boiling (the difference in boiling point between the pure refrigerant
and the mixture at the same pressure) should be as large as possible.
 Transport properties that influence heat and mass transfer, e.g., viscosity, thermal
conductivity and diffusion coefficient should be favourable [source from.

Lithium bromide-water (Li Br-H2O)

Advantage

 Lithium bromide acted as an absorbent is non-volatile. Hence used for avoiding

rectifying requirement
 Water which acts as refrigerants has high latent heat of vaporization
 Lithium bromide- water comparatively simpler to operate at high coefficient of
performance
 Requiring less pumping power
 Lithium bromide-water is non-toxic& non flammable
 It has the highest coefficient of performance (COP) compared to other single stage
absorption units at the same cycle temperatures.
 A basic generator is sufficient due to the non-volatility of absorbent(Li Br) allowing
only water vapour to be driven off the generator

Disadvantage

 Used only for air conditioning application, since water freezes at 0℃

 The solution is corrosive

G/HANNES T. And KINDALEM T. Page xxxvii

 DESIGN of SOLAR COOLING SYSTEM for AIR 2015
HANDLING UNITS of GARMENT ROOMS’ AC SYSTEM

 The system works only under high vacuum condition in condenser and evaporator
 The system requires water cooled condenser
 Very expensive
 Crystallization due to high pressure in generator low pressure in evaporator

Aqueous ammonia (ammonia-water solution) absorption system (NH3-H2O)

Advantage:-

 It is widely available
 Has very huge negative deviation from Roult’s law
 Has lower mar weight
 High heat of vaporization of refrigerant
 Water which acts as absorbent has very high affinity for ammonia
 Non expensive
 Used for air conditioning system, for preserving food
 NH3 is non-ideal solution etc.

Disadvantage

 Rectifying system is required since water is volatile

 Required pumping of working fluids from the absorber pressure to generator
pressure
 NH3 cannot be employed in a direct expansion evaporator coil and requires a
separate chilled water loop.

At this moment the amount of ammonia-water vapour absorption system is used most
widely in domestic refrigerator and industrial units because of the following important
points.

 NH3 is highly soluble in water

 Solubility of ammonia decreases as water TO increase and increases as water TO
decreases
 The amount of ammonia that will go in to solution with water decreases as
pressure decreases at constant TO
 The amount of ammonia that will go in to solution with water increases as pressure
increases at constant TO
 The weight of the solution decreases as more ammonia is added

G/HANNES T. And KINDALEM T. Page xxxviii

 DESIGN of SOLAR COOLING SYSTEM for AIR 2015
HANDLING UNITS of GARMENT ROOMS’ AC SYSTEM

 The vapour pressure of ammonia-water solution is less than that of pure ammonia
at the same TO
 Heat is generated during the formation of ammonia-water solution.
Properties of ammonia

 Liquid in nature
 It is available as refrigerant b/c it has low boiling point
 Non ideal
 More soluble in water
 No detectable
 Low in cost
 Its boiling point is -33℃ at normal atmospheric pressure
 Has low specific volume
 Has high density
 Is flammable
 Has some toxicity
 Has low molecular weight since it is normally used in refrigerant form
 Has high enthalpy of vaporization
 Has excellent chemical stability
 Has low viscosity

Properties of water

 Liquid in nature
 Available as refrigerant and absorbent
 It’s boiling and freezing point at normal atmospheric pressure is 100℃and 0℃
respectively.
 It is volatile in nature
 Has low viscosity
 Has low specific heat of vaporization
 Low in cost if it is used as refrigerant
 It is high solubility refrigerant when lithium -bromide is used as absorbent
 Has good chemical stability
 It is corrosive when it react with oxygen
 It is non flammable
 Naturally, it is non-toxic

G/HANNES T. And KINDALEM T. Page xxxix

 DESIGN of SOLAR COOLING SYSTEM for AIR 2015
HANDLING UNITS of GARMENT ROOMS’ AC SYSTEM

Lithium –bromide

o It is solid in nature which is salt

o Available as absorbent
o It is non-ideal solution
o It is non volatile
o Non flammable, but expensiv

CHAPTER-THREE

Selection of components for solar absorption cooling system

As we have been discussed in above definition there are a number of solar cooling systems.
The main common types are:

 Solar photo voltaic system

 Solar absorption refrigeration system
 Compression refrigeration system

Selection criteria’s

 Manufacturing system
 Operation
 Environmental friendly
 Reliability maintainability
 Cost effectively etc.
 Thermally working system

G/HANNES T. And KINDALEM T. Page xl

 DESIGN of SOLAR COOLING SYSTEM for AIR 2015
HANDLING UNITS of GARMENT ROOMS’ AC SYSTEM

Therefore; solar absorption refrigeration is the most common solar cooling system which
satisfied the above criteria’s.

3.1 Condenser

Condenser is an important component of any refrigeration system. In a typical refrigerant

condenser, the refrigerant enters the condenser in a superheated state. It is first de-
superheated and then condensed by rejecting heat to an external medium. The refrigerant
may leave the condenser as a saturated or a sub-cooled liquid, depending upon the
temperature of the external medium and design of the condenser.

Refrigeration cycle: The high pressure superheated gas is cooled in several stages in the
condenser.

Functions of condenser

 The condenser removes and dissipates heat from the compressed vapour to the
surrounding water to condense the refrigerant vapour to a liquid.
 Condenser is heat exchanger.
 Function of condenser is to get rid of heat absorbed previously and liquefy the
refrigerant.
 The vapour refrigerant condenses back to liquid at constant pressure.

3.2Types of condensers

There are three types of condensers these are:

 Air cooled condenser

 Water cooled condenser
 Evaporative condenser

3.2.1Air cooled condenser

As the name implies, in air-cooled condensers air is the external fluid, i.e., the refrigerant
rejects heat to air flowing over the condenser. Air-cooled condensers can be further
classified into natural convection type or forced convection type

In air cooled condenser, heat is rejected (removed) by air using either natural circulation or
forced circulations.

G/HANNES T. And KINDALEM T. Page xli

 DESIGN of SOLAR COOLING SYSTEM for AIR 2015
HANDLING UNITS of GARMENT ROOMS’ AC SYSTEM

3.2.1.1 Materials used to made air cooled condenser

Steel tubing, Copper tubing& Aluminium tubing

These types of condenser provided with time to improve air side heat transfer.

The refrigerant flows inside the tube and the air outside the tube

3.2.2Water cooled condenser

In water cooled condensers water is the external fluid. Depending upon the
construction, water cooled condensers can be further classified into:

1. Double pipe or tube-in-tube type 2. Shell-and-coil type, 3 Shell-and-tube type

Double Pipe (tube-in-tube type)

Double pipe condensers are normally used up to 10 TR capacities. In these condensers the
cold water flows through the inner tube, while the refrigerant flows through the annulus in
counter flow. Headers are used at both the ends to make the length of the condenser small
and reduce pressure drop. The refrigerant in the annulus rejects a part of its heat to the
surroundings by free convection and radiation. The heat transfer coefficient is usually low
because of poor liquid refrigerant drainage if the tubes are long.

Shell-and-coil type

These condensers are used in systems up to 50 TR capacities. The water flows through
multiple coils, which may have fins to increase the heat transfer coefficient. The refrigerant
flows through the shell. In smaller capacity condensers, refrigerant flows through coils
while water flows through the shell. When water flows through the coils, cleaning is done
by circulating suitable chemicals through the coil.

Shell-and-tube type

This is the most common type of condenser used in systems from 2 TR up to thousands of
TR capacity. In these condensers the refrigerant flows through the shell while water flows
through the tubes in single to four passes. The condensed refrigerant collects at the bottom
of the shell.

The coldest water contacts the liquid refrigerant so that some sub cooling can also be
obtained. The liquid refrigerant is drained from the bottom to the receiver. There might be a

G/HANNES T. And KINDALEM T. Page xlii

 DESIGN of SOLAR COOLING SYSTEM for AIR 2015
HANDLING UNITS of GARMENT ROOMS’ AC SYSTEM

vent connecting the receiver to the condenser for smooth drainage of liquid refrigerant. The
shell also acts as a receiver. Further the refrigerant also rejects heat to the surroundings from
the shell. The most common type is horizontal shell type.

3.2.3 Evaporative condenser

In evaporative condensers, both air and water are used to extract heat from the condensing
refrigerant. Evaporative condensers combine the features of a cooling tower and water-
cooled condenser in a single unit. In these condensers, the water is sprayed from top part on
a bank of tubes carrying the refrigerant and air is induced upwards. There is a thin water
film around the condenser tubes from which evaporative cooling takes place. The heat
transfer coefficient for evaporative cooling is very large. Hence, the refrigeration system can
be operated at low condensing temperatures (about 11 to 13 K above the wet bulb
temperature of air). The water spray counter current to the airflow acts as cooling tower. The
role of air is primarily to increase the rate of evaporation of water. The required air flow
rates are in the range of 350 -500 m3/h per TR of refrigeration capacity.

Evaporative condensers are used in medium to large capacity systems. These are normally
cheaper compared to water cooled condensers, which require a separate cooling tower.
Evaporative condensers are used in places where water is scarce. Since water is used in a
closed loop, only a small part of the water evaporates. Make-up water is supplied to take
care of the evaporative loss. The water consumption is typically very low, about 5 percent of
an equivalent water cooled condenser with a cooling tower. However, since condenser has
to be kept outside, this type of condenser requires a longer length of refrigerant tubing,
which calls for larger refrigerant inventory and higher pressure drops. Since the condenser is
kept outside, to prevent the water from freezing, when outside temperatures are very low, a
heater is placed in the water tank. When outside temperatures are very low it is possible to
switch-off the water pump and run only the blowers, so that the condenser acts as an air
cooled condenser.

Materials used to make water cooled condenser

 Shell is made of steel

 Tube is made of either copper or aluminium
 Tube is made of either copper or aluminium

G/HANNES T. And KINDALEM T. Page xliii

 DESIGN of SOLAR COOLING SYSTEM for AIR 2015
HANDLING UNITS of GARMENT ROOMS’ AC SYSTEM

Table 3.1 types of condenser

Types of condensers
Air cooled Water cooled Evaporative
condenser(ACC) condenser(WCC) condenser(EC)
Advantage: -it is sufficient& free cold -uses water rather than air -reduces water
surface since water conducts more Pumping-
-easy to install heat than air and chemical treatment
-used for reducing -it is smaller in size than with refrigerant-
environmental pollution ACC condenser system
-low maintenance cost -can operate at lower -needs less labor than
depends on application condensing TO than EV&ACC ACC
-uses air as cooling -consumes less energy per -more energy saving-
medium hose power than ACC(save than both ACC&WCC
-requires no water energy) -requires less fan power
-adequate supply of fresh -lower condensing- than ACC
air required pressure than ACC&EV -can operate at lower
-condensing air will not -WAC is more compact- than condensing TO than
freeze ACC ACC
-no need for mechanical -keeps the head pressure low -there is no down time
room -less noise and vibration requirement for annual
-condenser pumps not -cost effective cleaning
needed -needs the least labor -easy to maintain than
-install cost is the lowest -better control over WCC depending on
of all condensing pressure applications
-cooling tower not needed -higher efficiency than ACC -it is environmentally-
-larger tonnage capabilities benefit
than ACC -highly effective than
-refrigeration containment both ACC & WCC
-indoor placement
Usually have a longer life
than ACC

Types of condensers
Air cooled Water cooled Evaporative
condenser(ACC) condenser(WCC) condenser(EC)
Disadvantage: -generally the least -water -impurities in the vapor
efficiency compared to velocity(cavitations inside may cause corrosion
both WCC and EV the condenser tube - higher in cost compare
-life span is not as long damage condenser the rest
-usually have the most -at low operating TO
operating noise condensing medium&
-as water condenses it Condensate may freeze
has the risk of freezing -additional maintenance
at low operating TO costs
- change in air TOmay -water treatment cost
causes the condensing -mechanical room needed

G/HANNES T. And KINDALEM T. Page xliv

 DESIGN of SOLAR COOLING SYSTEM for AIR 2015
HANDLING UNITS of GARMENT ROOMS’ AC SYSTEM

pressure fluctuate - illegal in some areas

-requires space to because of high water
breathe and good usage
ventilation -uses high amount of
-under counter units water if not used with a
can draw floor dust in cooling tower
to refrigeration system
while modular units
must cool using hotter
air higher up

The condenser will be used to reject heat from the vaporized refrigerant to thesurrounding.
In conjunction with the raised pressure in the system after desorption, the condenser plays a
crucial role in completing the cycle so the process can repeat.

Selection criteria

 Cooling load
 Refrigerant used
 Source and temperature of available cooling fluid
 Quantity of refrigerant being circulated
 Condenser location
 Required operating pressure
 Maintenance consideration

Based on these criteria’s air-cooled condenser is found to fit for this case.

Heat transfer process in air-cooled condenser

1. De super heating
2. Condensing
3. Sub cooling

A 10% in decease in initial ∆T will give 8% increase in capacity

Material selection

The vast availability of steel in various shapes and sizes in remote regions around the world
makes steel a viable option for each component. The disadvantage of this readily available
material is its relatively poor heat transfer properties.

G/HANNES T. And KINDALEM T. Page xlv

 DESIGN of SOLAR COOLING SYSTEM for AIR 2015
HANDLING UNITS of GARMENT ROOMS’ AC SYSTEM

 Copper, Steel& Aluminium

The corrosive and deteriorative effects of ammonia over copper makes steel ideal for use in
Ammonia-water refrigeration systems. Steel AISI 1010 is the found to fit for the preset
requirements.

3.3 Expansion valve

An expansion valve is a device used for reducing or lowering the temperature and pressure
and pressure of a given fluid to the required once.

3.4 Types of expansion valves

3.4.1Capillary tube

A capillary tube is a small bore that provides restriction between the outlet of the condenser
and inlet of the evaporator by reducing the outlet of the condenser and inlet of the
evaporator by reducing the pressure. The capillary tube produces a refrigerant pressure drop
proportional to the square of the fluid velocity, which increases as the specific volume of the
refrigerant increases it is sometimes soldered to the outer surface of the suction line for heat
exchanger purpose.

Functions of Capillary tube

 The capillary tube has the function of transporting the working liquid from the
condenser to the evaporator.
 The small diameter and long length of the tube produces a large pressure drop. It is a
constant-restriction type expansion device.
 It controls the flow of refrigerant into evaporator.

They are simple, inexpensive and have no moving parts.

G/HANNES T. And KINDALEM T. Page xlvi

 DESIGN of SOLAR COOLING SYSTEM for AIR 2015
HANDLING UNITS of GARMENT ROOMS’ AC SYSTEM

Figure 3.2 capillary tube

3.4.2Thermostatic expansion valve (TEV)

The TEV is the automatic valve that maintains proper flow of the refrigerant in the
evaporator as per the load inside the evaporator. It is one of the most commonly used
throttling devices in the refrigerator and air conditioning systems. If the load inside the
evaporator is higher it allows the increase in flow of the refrigerant and when the load
reduces it allows the reduction in the flow of the refrigerant. This leads to highly efficient
working of the compressor and the whole refrigeration and the air conditioning plant

The thermostatic expansion valve has a moving plug, which controls the area available for
flow. .this valve performs following functions.

I. Throttling action: thermostatic expansion valves separate the high pressure &
low-pressure sides of the system. This pressure difference between the
condenser and evaporator permits throttling.
II. Modulation action : valve feeds the evaporator with liquid refrigerant at the
proper rate all times .if too much refrigerant passes the evaporator not all will
change into vapour and if too low refrigerant enters the evaporator there will
be not enough liquid to absorb heat at evaporator ,reducing the system
capacity
III. Controlling action: the valve responds to load changes at the evaporator.
IV. Reduce the pressure of the refrigerant from the condenser pressure to the
evaporator pressure
V. Keep the evaporator active: The thermostatic expansion valve allows the
flow of the refrigerant as per the cooling load inside it.
VI. Allow the flow of the refrigerant as per the requirements. It allows the flow
of the refrigerant to the evaporator as per the load on it.

3.4.3 Constant pressure expansion valve (CPEV)

The CPEV operates using evaporator valve discharge pressure. It controls mass flow rate
of the refrigerant entering the evaporator and maintains a constant evaporator pressure .it
should have an adjustable pressure range to provide the required evaporator pressure .it
normally is suitable only for constant pressure application.

G/HANNES T. And KINDALEM T. Page xlvii

 DESIGN of SOLAR COOLING SYSTEM for AIR 2015
HANDLING UNITS of GARMENT ROOMS’ AC SYSTEM

3.5 Evaporator

The evaporator transfers heats from the fluid or being cooled to the boiling refrigerant.
Various types of refrigerants are commercially available. The evaporator is the element of
the system that is contained within the cold volume. Good heat transfer between it and its
surroundings are essential to its function. But most importantly, it must be designed such
that it can withstand the vacuum pressures it will experience.

Refrigeration cycle

Functions of Evaporator:

 Evaporator is a device in which the refrigerant is boiled by extracting heat from

surrounding medium.
 It is the cooling unit, and some time called the cooling coil, freezing coil etc.
 The liquid refrigerant from expansion valve enters into evaporator coil at a
temperature below the temperature of evaporator.
 It extracts heat from evaporator and produces coldness Low pressure liquid
refrigerant in evaporator absorbs heat and changes to a gas.

3.6Types of evaporators
A. Direct expansion finned tube (Shell-and-Coil type evaporator)
B. Shell and tube C. Flooded Evaporator D. Double pipe type evaporator

E. Plate Surface Evaporators F. Plate type evaporators

G. Baud lot type evaporators

From the above types of evaporators, direct expansion finned tube & Shell and tube are the
most common.

3.5.1 Direct expansion finned tube

Extended surface coil or simply coil consists of rows of tubing through which the
refrigerants flows and over which the air flows.

These types can be with both natural convection and forced convection air movements thus
can be used for liquid-gas and gas-gas pairs.

3.5.2 Shell and tube

G/HANNES T. And KINDALEM T. Page xlviii

 DESIGN of SOLAR COOLING SYSTEM for AIR 2015
HANDLING UNITS of GARMENT ROOMS’ AC SYSTEM

Shell and tube: has a metallic shell through which water being flows through. This type uses
liquid-liquid, liquid-gas and gas-gas pairs.

Selection criteria’s

 Heat transfer requirements

 Economical effective Cost
 Physical size
 Physical drop characteristics like freezing point
 Maintenance

For this evaporator selection the one that meets the listed criteria’s mentioned above is
direct expansion finned tube type with natural convection is selected because the forced
convection type need fan& pump for fluid movement(air & water).

3.7 Heat exchanger

Is a device built for efficient heat transfer from one media to another. There are not only
used in heating application, but such as space heaters, but are also used in cooling
applications, such as refrigerators, and air conditioners.

3.8 Classifications of heat exchangers based on the direction of liquids flow

Parallel flow: both fluid involved move in the same direction, entering and exiting the
exchanger side by side.

Cross flow: the fluid paths run perpendicular to one another.

Counter current: the fluid paths flow in opposite directions, with each exiting where the
other enters. They tend to be more effective than other types of exchanger.

3.9 Types of heat exchangers

 Shell and tube heat exchanger

 Plate heat exchanger
 Regenerative heat exchanger

G/HANNES T. And KINDALEM T. Page xlix

 DESIGN of SOLAR COOLING SYSTEM for AIR 2015
HANDLING UNITS of GARMENT ROOMS’ AC SYSTEM

The most common types of heat exchangers which are used in heating and cooling system
are shell and tube and plate heat exchangers.

3.9.1 Shell and tube heat exchanger

is one type of counter flow heat exchanger which consists of series of tubes. One set of this
tube contains fluid that must be heated cooled. The second fluid runs over the tubes that are
being heated or cooled so that it can either provide the heat or absorb the heat required.

3.9.2 Plate heat exchanger

is another type of heat exchanger composed of multiple, thin, slightly separated plates that
have very large surface are small as and fluid flow passage for heat transfer. It is most used
in refrigerating and air conditioning application and it is the most effective comparing to the
other type heat exchangers.

3.10 Selecting criteria’s for heat exchangers

In order to achieve optimum process operations, it is essential to use the right of process
equipment in any given process. The following criteria’s can help in selecting the type of
EXHS best suited for a given process.

 Applications (i.e sensible vapour or liquid, condensing or boiling)

 Operating pressure and temperature(including start up shut down, normal and
process up set conditions)
 Fouling characteristics of the fluid (i.e tendency to foul due to temperature and
suspended solid )
 Parches cost
 Installation cost
 Operating cost(pumping and fan)
 Maintenance cost

Based on these criteria’s plate heat exchanger is found to fit for this case

3.11Absorber

After passing through the generator, the super heated refrigerant NH 3 and the absorbent H2O
are separated by rectifier. If any of the H 2O under goes phase change (to steam), it needs an
extra component called a rectifier. In any way the mixture enters the rectifier and get

G/HANNES T. And KINDALEM T. Page l

 DESIGN of SOLAR COOLING SYSTEM for AIR 2015
HANDLING UNITS of GARMENT ROOMS’ AC SYSTEM

pressurized so as to help the super heated NH 3 escape easily and the weak ammonia solution
to return to the absorber for absorption purpose through the heat exchanger and pressure
reducing valve( expansion valve). The absorber is the component where the weak ammonia
solution separated from the vapour refrigerant at the heat exchanger is accumulated and
absorbs the evaporated refrigerant (the refrigerant after giving refrigeration effect) so that it
will keep circulating through the cycle. The strong solution in which it is exists from
absorber to solution pump. The absorber should be capable of holding the flow of
refrigerant and weak refrigerant solution from evaporator and respectively. It consists of a
bundle of tubes, which are cooled by water or air.

3.12 Solution pump (bubble pump)

Solution pump is a device that is used raise liquid from one location to other higher location
without mechanical energy; instead, it utilized thermal energy to power this change in
position by increasing the buoyancy of the fluid, it is moving.

A single pressure absorption cycle does not require mechanical work to pump fluid from the
absorber to the higher-pressure generator. However, the single pressure cycle does require a
mechanism to lift the fluid from the generator to the absorber against gravity and friction. A
bubble pump, or vapour-lift pump, is used for this task because it requires only thermal
energy input as the driving force, which is the same as that required to drive the absorption
cycle.

In a bubble pump, heat addition creates vapour, thereby increasing the buoyancy of the fluid
causing it to rise through a vertical tube under two-phase flow conditions. Airlift pumps
have been used for decades in the oil industry that run on the same principles, however
instead of bubbles forming from the phase change involved with boiling the liquid, air is
injected into the flow, creating the same buoyancy effect.
While two-phase vertical flow and airlift pumps have been studied since the early part of the
last century, no references studying the design optimization of a bubble pump are found in
the open literature. The best-suited model is used to carry out parametric studies and to
optimize for maximum efficiency under various operating conditions. Optimum efficiency
is defined as the liquid pumped per unit of bubble pump heat input. The results show there is
an optimum bubble pump tube diameter for a given set of operating conditions.

G/HANNES T. And KINDALEM T. Page li

 DESIGN of SOLAR COOLING SYSTEM for AIR 2015
HANDLING UNITS of GARMENT ROOMS’ AC SYSTEM

Despite there being no need to pump the fluid to a much higher pressure to create a change
in saturation temperature, a mechanism is needed to move the fluid through the cycle against
flow friction and gravity. To eliminate the need for a mechanical input, a heat driven bubble
pump is used for this purpose.
While many pump use mechanical means by which to move a fluid (either liquid or air).
This pump is very important for our project because of the following criteria’s. It is
1. Simple in construction with few moving components
2. Reliable in its failure
3. Simple to maintain and cost effective in maintenance
4. Low cost in manufacturing
5. In general it is effective in its cost
3.13 Generator

A generator is needed in the absorption cycle to separate the refrigerant vapour from the
liquid solution before the refrigerant enters the condenser. This involves heat transfer from a
relatively high-temperature source. The refrigerant then flows to the condenser, while the
absorbent is throttled back to the lower pressure as it falls to the absorber [28].

They are able to completely avoid the need for electric power, along with its associated
central power plant and electric distribution infrastructure and instead rely on a direct
thermal energy source.
This helps avert the need to wastefully convert heat to work and then back to heat. They also
use environmentally benign fluids, an increasingly important issue as several manmade
refrigerants are phased out over the next few years. Additionally, they are portable, reliable,
operate silently and are inexpensive to build. However, with relatively low refrigeration
COP’s, they have limited applications. When used for heating, both cycles can achieve
efficiencies over 100%. In this situation, when competing against direct-fired heating
devices, the low COP is less of an issue [28, 2].
For the separation of the working fluids i.e. the refrigerant from the absorber it needs heat
(thermal energy). This energy can be given from many sources. Of these to mention few
coal, fossil fuels, petroleum and crude oil, geothermal energy, electrical energy and solar
energy .the availability and cost of these energy sources vary from place to place based on
the available natural resources of the specific location.

G/HANNES T. And KINDALEM T. Page lii

 DESIGN of SOLAR COOLING SYSTEM for AIR 2015
HANDLING UNITS of GARMENT ROOMS’ AC SYSTEM

For the design of the refrigerator, the heat energy source is the solar energy given from the
sun. Solar radiation is an integral part of different renewable energy resources, in general,
and, in particular, it is the main and continuous input variable from the practically
inexhaustible sun.

Solar energy is expected to play a very significant role in the future especially in developing
countries, but it also has potential in developed countries. The material presented in this
book has been chosen to provide a comprehensive account of solar energy modelling
methods. For this purpose, explanatory background material has been introduced with the
intention that engineers and scientists can benefit from introductory preliminaries on the
subject both from application and research points of view. For the proper utilization of the
energy, different mechanisms of tracking are used based on the total energy demand.

3.12 Rectifier

In case when the temperature of the absorber rises above 100 0c, then steam is generated and
this steam, instead of flowing to the absorber, goes up together with the vapour ammonia
through liquid-liquid heat exchanger. If this passes the bubble pump, it will condense on the
condenser thus enters the evaporator in a liquid water-ammonia mixture. This mixture of
liquid water with ammonia causes refrigeration effect to drop thus, reducing the overall
efficiency of the cycle. For this reason the steam should be separated from the vapour
ammonia. Rectifier is used for separating the two working fluids. The rectifier is selected
based on the flow rate i.e. how much m3of steam should be handled at given time [6].

3.13 Housing:
For good support of the refrigerating components and providing good heat transfer area
between air and the working fluid the housing is used. It can be made from wood or metals.

3.14 Piping selection

The piping system is required to join the different components at continuities, branches,
cornering or bending so that they are assembled to form one unit. Piping allows fluids to
flow in the required direction at a determined flow rate.

Cause and Effect of Pressure Drop

G/HANNES T. And KINDALEM T. Page liii

 DESIGN of SOLAR COOLING SYSTEM for AIR 2015
HANDLING UNITS of GARMENT ROOMS’ AC SYSTEM

Pressure drop occurs during fluid flow because of frictional forces within the fluid and
frictional forces between the moving fluid stream and the stationary pipe walls. The amount
of pressure drop depends on a number of variables, including:
 Type of flow e.g., laminar, turbulent, etc.
 Physical properties of fluid, e.g., viscosity, density, etc.
 Pipe characteristics, e.g., diameter, roughness, etc.
 Velocity of flow in pipe
Pressure drop increases in proportion to the length of pipe. Pressure drop is also increased
by anything, which disturbs the flow, such as valves, tees, elbows and other fittings. In
refrigerant piping, some pressure drop occurs in both vapour and liquid lines. These
pressure drops can have a significant impact on system performance. The effect of these
pressure drops must be anticipated and compensation made in the total design.
System design for minimum pressure drop.
Pressure loss results in:
a. decrease in thermal capacity
b. increase power requirements
Refrigerant being piped does not change state.

A Suction line must:

 Return refrigerant from the evaporator to the absorber at minimum system capacity.
 Prevent oil draining from an active to an inactive evaporator when more than one
evaporator is used in a single system.
 Minimize line sweating from condensation.
 Prevent unnecessary heat gain into the refrigerant.
The Hot Gas Discharge line must:
 Prevent backflow of liquid refrigerant to the thermal compressor during low capacity
or shutdown.
 Dampen or eliminate line vibration and noise caused by gas pulsations
 The Liquid line must prevent:
 Formation of flash gas upstream of the metering device.
 Heat gain to the refrigerant.
The refrigerant Condensate line must:
Provide sewer-type flow; that is, free draining of liquid refrigerant in one direction, while
refrigerant vapor flows adjacent to the liquid in the other direction.
The Hot Gas Defrost line must:

G/HANNES T. And KINDALEM T. Page liv

 DESIGN of SOLAR COOLING SYSTEM for AIR 2015
HANDLING UNITS of GARMENT ROOMS’ AC SYSTEM

 Maintain sufficient refrigerant flow rate. The velocity determined at saturated

conditions will result in a conservative line size.
 Be properly sized to handle the calculated needed hot gas load, this is based
on twice the evaporator flow rate.
 Prevent condensed liquid refrigerant from backflow to the thermal
compressor units while on defrost or shutdown.
Piping final selection:-
Before selecting from a Nomo graph or a standard table you must know the following facts:
 The system refrigerant type
 System design capacity
 Saturated Suction Temperature (SST)
 Saturated Condensing Temperature (SCT)
 Maximum allowable pressure drop for each refrigeration line
 Minimum allowable velocity for each refrigeration line
For this design, it is found that the following pipes should be used. Threaded galvanized
steel is the material of the pipes.

3.15 solar thermal collectors

3.15.1 Flat plate collector

Flat plate collectors developed by Hotel and Wilier since1950s, is one of the most common
type of solar collector. It consists of:

1. Dark flat plate absorber

2. Transparent cover that reduce heat losses
3. Heat transport fluid, air antifreeze or water to remove heat from absorber
4. Heat insulating backing.

The flat plate collectors are based on two important principles: a black base that absorbs the
solar radiation better than any other colour and a glass lid that is needed to keep the heat in.
Its surface should be located perpendicularly to the solar radiation direction for the
maximum solar energy gain. Here the sun’s rays go through the glass cover and the air layer
to warm up the black metal plate, which in turn warms the water. Unfortunately, the
ordinary metal plate is also warmed up. The heat insulation lagging keeps most of the heat
inside the sandwich. With the heat in the water ammonia solution, it has now to be moved to

G/HANNES T. And KINDALEM T. Page lv

 DESIGN of SOLAR COOLING SYSTEM for AIR 2015
HANDLING UNITS of GARMENT ROOMS’ AC SYSTEM

where good use can be made of it. Its operation is based on the simple fact that hot water
ammonia solution will rise to settle above a quantity of water ammonia solution at lower
temperature.
As the collector heats up, the super-heated ammonia and heated water in it rises out at the
upper pipe and pushes its way into the top of the tank or the bubble pump. This heat-induced
circulation is completed as the water, being pushed down the bubble pump, comes round the
bottom and back into the collector. Among the different types of solar collectors, the most
primitive is unglazed panels, which are most suitable for swimming pool heating where it is
not necessary for the collectors to raise the temperature of the water to more than a few
degrees above ambient air temperature, so heat losses are relatively unimportant.
In practice, most often the collectors do not move, and therefore, they must be located such
that during one day the maximum amount of solar radiation can be converted into solar
energy. For this reasons, fixed collectors must be located to face south (north) in the
northern (southern) hemisphere. This implies that for given latitude there is a certain angle
which yields the maximum solar energy over the year. As a practical rule, for low latitudes
the angle of the collector is almost equivalent to the angle of latitude, but increases by 10° at
40°N and 40°S latitudes. All these arrangements are for flat-surfaced collectors. Typical
temperatures that can be achieved by flat plate collectors vary between 40°C and 120°C [8].

Advantages of flat plate collector

1) Will absorbs energy coming from all directions above absorbers(both beam and
diffusion solar radiations)
2) Received more solar energy than two point solar collector
3) It is more effectively in cost than two point solar collector
4) Since tracking is not required it may be firmly fixed to mounting structure

Disadvantage

1) Due to lack of tracing mechanism, it has greater cosine losses

2) Gives total energy falls on fixed surface that tracks one or two axis
3) Gives less output energy than others and gives less efficiency
4) Its change of TO is maximum
5) Gives less output TO and high in put TO

G/HANNES T. And KINDALEM T. Page lvi

 DESIGN of SOLAR COOLING SYSTEM for AIR 2015
HANDLING UNITS of GARMENT ROOMS’ AC SYSTEM

Figure 3.3 flat plate collectors

3.15.2 The parabolic dish system

A parabolic dish system, or solar dish, as they are sometimes known, is composed of a
single structure supporting a parabolic dish covered in mirrors that reflect light on to a solar
receiver located at the focal point of the dish. Solar dishes are being developed mainly for
electricity generation and, therefore, the solar receiver is combined with the energy
conversion element which is usually a thermal engine, such as a Sterling engine or a Bray
ton cycle engine. It one of the most power full collector which concentrates sun light at a
single focal point via one or more parabolic dish arranged in a similar fashion to a reflecting
telescope focus straight or dish antenna focuses radio waves. Parabolic dish system consists
of a parabolic shaped point focus concentrator in the form of a dish that reflects solar
radiation on a receiver mounted at the focal point (the power conversion unit).this system
produces small amount of power electricity (3kwattto25kwatt) compared to the other
concentrating solar power technology. There are two key phenomena to understand in order
to comprehend the design of a parabolic dish. One is that the shape of the parabola is
defined such that incoming rays which are parallel to the dish axis will be reflected towards
the focus no matter where on the dish they arrive. The second key is that the light rays from
the sun arriving at the earth’s surface are almost completely parallel [5,8].

Advantage

 Good efficiency: by concentrating sunlight current system can get better

efficiency than simple solar cells.
 Very high temperature reached (up to300℃): conversion efficiency approaching
30 percent has been achieved.

G/HANNES T. And KINDALEM T. Page lvii

 DESIGN of SOLAR COOLING SYSTEM for AIR 2015
HANDLING UNITS of GARMENT ROOMS’ AC SYSTEM

 A larger area can be covered by using relative in expensive mirror rather than
using expensive solar mirror
 The solar parabolic dish stiriling engine system has only a very minimal water
requirement. The engine air cooled so no cooling water is needed.
Disadvantage

 Concentrating system requires sun tracking to maintain sun light focus at the
collector.
 Inability to provide power in diffused light condition.
 Heat to electricity conversion requires moving parts and those results in maintenance

Figure 3.4 parabolic dish collector

3.15.3the parabolic trough collector

This is the simplest form of CSP system, where the solar collector field is composed of rows
of trough shaped solar collector elements, usually mirrors, with an integral receiver tube.
They are parabolic in one dimension only and form a long parabolic shape. The collectors
are usually installed in rows and the total solar field is composed of several parallel rows.
The collectors are connected to a single motor, controlled by a solar tracking control system,
which ensures that the maximum amount of sunlight enters the concentrating system
throughout the day. The solar receiver is a black-coated, vacuum glass tube containing the
heat transfer fluid, either oil or water. The concentrated sunlight heats the heat transfer fluid,
which can then be used to generate electricity using a turbine and an electrical generator.

Generate high-pressure superheated steam. The superheated steam is then fed to a bubble
pump to be pumped itself for better circulation. The spent steam is condensed in a standard

G/HANNES T. And KINDALEM T. Page lviii

 DESIGN of SOLAR COOLING SYSTEM for AIR 2015
HANDLING UNITS of GARMENT ROOMS’ AC SYSTEM

condenser and returned to evaporator via gravity advantage on putting it by height

difference to be transformed back into steam. Condenser cooling is provided by natural
convection air cooling system. In the evaporator, the main target of the project or the
refrigeration effect takes place. Historically, parabolic trough plants have been designed to
use solar energy as the primary energy source to produce electricity. The plants can operate
at full rated power using solar energy alone given sufficient solar input. During summer
months, the plants typically operate for 10 to 12 hours a day at full-rated electric output.
However, to date, all plants have been hybrid solar/fossil plants; this means they have a
backup fossil-fired capability that can be used to supplement the solar output during periods
of low solar radiation. The fossil backup can be used to produce rate dielectric output during
overcast or night-time periods.[8,5]

Advantages of parabolic trough solar collector (PTSC)

Comparing with the other types of solar collectors, PTSC is the most concentrating solar
power technology being developed in order to increase fluid temperature and thus the most
efficient for solar plant conversion of solar power to electricity. Solar parabolic trough
system is the most developed and commercially tested solar power technology up to
350Mwpower can be generated. The advantages of PTSC over the other solar thermal
collectors are listed below.

 With low cost can gave high thermal efficiency up to 80.

 Produce high steam generating electricity with conventional Rankine steam cycle
which is readily hybridized; that it can be set up to use a fossil fuel typically
natural gases.
 Sound created by this collector is smallest enough.
 Provides high temperature
 Reduces the need for using heat transfer medium for heating the working fluid
pairs
 High energy generation is as possible.
The parabolic solar collector is the most suitable for use in an integrated solar combined
cycle system with potential to reduce the cost and to increase over all solar to electric
efficiency.

G/HANNES T. And KINDALEM T. Page lix

 DESIGN of SOLAR COOLING SYSTEM for AIR 2015
HANDLING UNITS of GARMENT ROOMS’ AC SYSTEM

Figure 3.5 parabolic trough collectors

1. Reflector material (Mirror) 2. collector plate

3. Support plate 4. Absorber tube

5. Bearing support

Selection criteria’s

The selection of solar thermal collector is based on the following criteria’s

These are:

a. Durability
b. Maintainability
c. Environmental safety
d. Cost effectively
e. Change in temperature and so on

Therefore; Comparing with the other types of solar collectors, parabolic trough is the best
and most concentrating solar power technology being developed in order to increase fluid
temperature and thus the most efficient for solar plant conversion of solar power to
electricity. It is also agreed with the above criteria’s

Two types of solar water heating systems are available. These are:

Direct or open loop systems, in which potable water is heated directly in the collector.

Indirect (or closed loop systems), in which potable water is heated indirectly by a heat
transfer fluid that is heated in the collector and passes through a heat exchanger to transfer
its heat to the domestic or service water. In this project then, we have selected way of that

G/HANNES T. And KINDALEM T. Page lx

 DESIGN of SOLAR COOLING SYSTEM for AIR 2015
HANDLING UNITS of GARMENT ROOMS’ AC SYSTEM

the solar water heater system works is based on the Indirect (or closed loop systems) in
which the ammonia is heated indirectly by a heat transfer fluid that is heated in the collector
and passes through a heat exchanger to transfer its heat and to cool it in order perform
whether domestic application or to give important services for other applications.

In order to do so the design of Parabolic Trough collector is necessary to meet the main
objective of this project. The input temperature of the parabolic trough collector is estimated
to 50℃& the output temperature is reached up to 400℃(which is an expected out let
temperature).

Material Selection

The following are the basic materials needed to construct the parabolic trough collectors.

 Aluminium sheet(3.3mm in thickness)

 Absorber tube (Receiver)
 Support frames
 Mirrors
 Absorber cover
Aluminium sheet

It is apart that reflects solar rays back to the focus in which the base will be aluminium sheet
formed in parabolic structure and attaching the mirrors over it.

Aluminium is chosen because of its:

 excellent resistance of corrosion,

 excellent sound and heat insulation,
 surfaces smoothness, superior weather,
 excellent bending process,
 easy to maintain
 Super peeling strength
 better thermal conductivity and
 Lighter in weight because while designing this devise it should be noted that cost
effective with good efficiency. The thickness (ranging from2mmto6mm), width
(ranging from1220mm 1600mm) and length (2400m-6000mm) of aluminium sheet
are from standard.

G/HANNES T. And KINDALEM T. Page lxi

 DESIGN of SOLAR COOLING SYSTEM for AIR 2015
HANDLING UNITS of GARMENT ROOMS’ AC SYSTEM

Absorber tube Materials for absorber

1) Cu 2. Al 3.Steel

Criteria’s

i. high melting point

ii. good yielding stress
iii. cost effective
iv. less energy consumption
v. which is strong

Absorbers for parabolic trough are mostly selected to be copper because they have the
ability to capture the energy collected or locally made material like steel can be used painted
black to increase its performance. But for this particular purpose copper is used as absorber
on the trough. Therefore; copper is the best one.

Materials for reflecting (mirrors)

Mirrors (are one types of reflecting materials) in a cube form are cut in small pieces
attaching on the parabolic aluminium sheet structure to reflect the solar radiation from the
sun coming to the trough to the absorber tube at the focal length. The area of the mirror is
the same as the area of the parabolic shape of aluminium sheet.

For reflecting system, high quality and good secular reflectance properties are required to
achieve good result and to insure long life of the system.

In order to give effective accumulation the following criteria should be fulfilled

Criteria’s

a. Dust and contamination should be removed b. Stability of reflective coating

d. Environmental effective c. Cost effective

Varieties of mirrors in use for reflecting system

1) The glass reflector 3.Metalized plastic film (in general aluminized)

2) Polished aluminium surface 4.Metallic surface(stain less steel)

Therefore; from the above mirrors the most important is polish aluminium surface and
(reflects 80-85).

G/HANNES T. And KINDALEM T. Page lxii

 DESIGN of SOLAR COOLING SYSTEM for AIR 2015
HANDLING UNITS of GARMENT ROOMS’ AC SYSTEM

Types of glasses: Soda lime, Lead alkali Borosilicate, Alumina silicate & Sliver

In this case, sliver is the metallic reflecting which coating that is commonly applied and is
used on the second surface mirror (glass) [8].

Absorber cover
The cover used for this collector is that to reduce the convective heat losses from the hot
steel pipe. It is made of glass cube with a frame to support each other.

Function of absorber cover

 To transmit maximum solar energy in to the absorber

 To minimize up ward heat loss from the absorber
 To shield the absorber plate from direct exposure to weathering

Material selection

The transparent plastic materials used for constructing cover plate are:

I. Acrylic polycarbonate plastic

II. Plastic film of Tedlar and Mylar
III. Commercial plastic like lexan
IV. Temper glass

Criteria’s: The most critical factor selecting for cover plate materials are based on the
following criteria’s

a. Durability e. Non-degradability
b. Solar energy transmittance f. Economical cost
c. Maintainability g. Reduction in weight
d. Must be environmental friendly.
Based on these listed criteria’s temper glass is the most important in which it is
helped for constructing the cover plate.

G/HANNES T. And KINDALEM T. Page lxiii

 DESIGN of SOLAR COOLING SYSTEM for AIR 2015
HANDLING UNITS of GARMENT ROOMS’ AC SYSTEM

CHAPTER-FOUR

Thermal and Conceptual design analysis

4.1Thermal analyses
4.1.1 Governing equations

The thermodynamic analysis of vapour absorption cycle is based on the following equations
that can be applied to any parts of the system. The available equations are given in the form
of tables.

Table 4.1 absorption-refrigeration calculation

Absorption refrigeration system calculation
Material balance(partial mass Mass balance Energy balance
balance)
∑ Ṁ =0 ∑ XṀ =O ∑ Q−m∗h=0
˙
Mass of weak solution
∑ ( Ṁw + D−F )=0
Quality of rich solution( ƒ )
F
ƒ=
D
quality of weak solution(y)
ƒ=1+ y
Coefficient of performance(COP)

G/HANNES T. And KINDALEM T. Page lxiv

 DESIGN of SOLAR COOLING SYSTEM for AIR 2015
HANDLING UNITS of GARMENT ROOMS’ AC SYSTEM

Qe
COP=
Qg

The governing equations for the complete absorption refrigeration cycle are given by
examining the balances of mass, energy and momentum for the different components in the
cycle.
A thermodynamic simulation of a solar absorption refrigeration cycle has been carried out.
The binary mixture considered in the present equation is H2O– NH3(water ammonia). This
simulation was performed in order to investigate the effect that the generator temperature
has over COP and mass flux on a single absorption refrigeration system that uses solar
energy as a primary source.

4.1.2 Phases of the refrigerant and absorbent in the cycle

The circuit diagram

The solar absorption refrigeration with a solution pump for refrigerant circulation is shown
in the schematic diagram below A-absorber
1. PS- solution pump, 4. C-condenser

2. EV-expansion valve 5. G-generator

3. EXH-heat exchanger (Regenerator) 6.A-Absorber

G/HANNES T. And KINDALEM T. Page lxv

 DESIGN of SOLAR COOLING SYSTEM for AIR 2015
HANDLING UNITS of GARMENT ROOMS’ AC SYSTEM

Figure 4.1diagram of solar absorption refrigeration

A typical single-effect absorption refrigeration cycle consists of four basic components, an

evaporator, an absorber, a generator and a condenser. The cooling cycle starts at the
evaporator, where liquefied refrigerant boils and takes some heat away with it from the
evaporator, which produces the “cold” desired in the refrigerated space. The refrigerant
vapour releases its latent heat as it is absorbed by a liquid absorbent in the absorber.

The flow in the pipes is assumed one- dimensional and no diffusion of heat occurs in the
flow direction. In addition, there is no heat loss from generator to the surroundings nor heat
gain by the evaporator from the surroundings and the expansion process in the valve is
assumed to occur at constant enthalpy. In the above figure shown, there are seven
fundamental states. These are:

State1: exit from generator and inlet to the rectifier (supper heated ammonia)

State 2: exit from rectifier and inlet to condenser saturated liquid ammonia)

State 3: exit from condenser and inlet to expansion valve (enthalpy is constant)

State 4: exit from expansion valve and to evaporator (cooling is taking place)

State 5: exit from evaporator and inlet to absorber (heat rejection in to the surrounding is
taking place)

G/HANNES T. And KINDALEM T. Page lxvi

 DESIGN of SOLAR COOLING SYSTEM for AIR 2015
HANDLING UNITS of GARMENT ROOMS’ AC SYSTEM

State 6: exit from absorber in to the generator (recycling process is taking place)

State 7: exit from heat exchanger and inlet to the absorber (weak solution cooling system is
taking place)

Mass balance and Energy balance

As shown in the above diagram the equivalent mass and energy of the working fluid in the
components is given by the table below

Table 4.2 mass and energy balance of each component

M. balance E. balance P=P Sat(T)

C ṁ2=ṁ3= ṁ ∑ QC =m ( h2−h3 ) =0 Pc=Psat ( Tc )

Qc=ḿ ( h 2−h 3 )

EV ṁ 3=ṁ 4 =ṁ
h3 =h4

E ∑ ṁe − ṁ4=0 Qe =ṁ4 ( h4 −h3 ) Pe=P sat ( Te )

ṁ3=ṁ4 =ṁ

A ∑ Q a+ ṁ ( 1+ λ ) h6 −ṁh 5−λ ṁ h7=0 pa= psat (T )

ṁ ss =m ws + ṁ 4= y ṁ 4 + ṁ 4 =( 1+ λ ) ṁ 4 Q =−ṁ ( 1+ λ )+ ṁh + λ ṁh
a 5 7

Where,

ṁ ws =¿Mass flow rate of weak

solution

y=circulationratio

ṁ=¿ Mass flow rate of refrigerant

Material balance (refrigerant
mass balance)

∑ ( ξ ss∗ṁss− ṁ4−( 1−ξ̇ ws )∗ṁws )=0

ξ ss˙ ṁss =ṁ+ ( 1+ ṁws )

G/HANNES T. And KINDALEM T. Page lxvii

 DESIGN of SOLAR COOLING SYSTEM for AIR 2015
HANDLING UNITS of GARMENT ROOMS’ AC SYSTEM

ξ ws
y=
ξ ss −ξws

PS ṁ5=ṁss = ṁ6 Work is negligible

∑ (ṁ7−ṁ1−ṁ8 )=0 Q g=ṁ NH × h1+ y ṁ NH h8−ṁ NH (1+ y)h7

3 3 3

G ṁ 7= ṁ1 + ṁ8

HEX ṁ 5=ṁ6= ṁ7 Energy is not mandatory to use

NB Heat cannot be destroyed or lost. However, it can be transferred from one body or
substance to another or to another form of energy. Since heat is not in itself a substance, it
can best be considered in relation to its effect on substances or bodies. When a body or
substance is stated to be cold, the heat that it contains is less concentrated or less intense
than the heat in some warmer body or substance used for comparison.

4.2 Conceptual design analysis

4.2.1 Basic earth sun angles

For calculating solar radiation and designing the solar device particularly parabolic trough
device, the knowledge of suns path in the sky on the various days in a year at a particular
place is a fundamental pre-request.

For complete specification of the suns position in the sky at the particular time we make use
of two angles, namely solar altitude angle & azimuth angle.

For most solar energy collector applications, a reasonable and accurate prediction of where
the sun will be in the sky at a given time of day and year is necessary to consider in the
design. In the Ptolemaic sense, the sun is constrained to move with 2 degrees of freedom on

G/HANNES T. And KINDALEM T. Page lxviii

 DESIGN of SOLAR COOLING SYSTEM for AIR 2015
HANDLING UNITS of GARMENT ROOMS’ AC SYSTEM

the celestial sphere; therefore, its position with respect to an observer on earth can be fully
described by means of two astronomical angles, the solar altitude (α) and the solar azimuth
(z). The following is a description of each angle, together with the associated formula.

Declination angle (δ)

Declination angle the angle between the sun earth centre line and the projection of this line
on the equatorial plane or it is the angular distance of the sun’s rays north (or south) of the
equator north declination designated as positive. It is an angular displacement of the sun
from the plane of the earth’s surface (equator). The variation of the solar declination
throughout the year is shown in Figure the declination (δ) in degrees for any day of the year
(N).As we in the figure below point O on the surface of the earth whose centre at O.

Figure 4.2 definitions of latitude, hour angle and solar declination

As shown in Figure above the declination angle (δ) in degrees for any day of the Year (N)
can be calculated by the following mathematical expression.

360 × ( N +284 )
δ =23.45 ° sin … … … … … … … … … … … … … … .4 .2 .1
365

Where, N is any day of the year

1 ≤ N ≤ 365

G/HANNES T. And KINDALEM T. Page lxix

 DESIGN of SOLAR COOLING SYSTEM for AIR 2015
HANDLING UNITS of GARMENT ROOMS’ AC SYSTEM

Figure 4.3declination angle of the sun

Figure 4.4 day number recommended average day for each month

Latitude (L)

Latitude is the angular location north or south of the equator, north positive -90°≤ɸ≤90° or it
is the angle between the axis and the reflected beam at the focus of the parabola or is the
angle made by the radial line, joining the given location to the Centre of the earth, with its
projection on the equatorial plane. The value taken for Mekelle is L= 13.48⁰.

Hour angle( h )

The angular displacement of the sun east or west of the local meridian due to rotation of the
earth on its axis at 15° per hour, morning negative, afternoon positive or it is a point on the
earth’s surface is defined as the angle through which the earth would turn to bring the

G/HANNES T. And KINDALEM T. Page lxx

 DESIGN of SOLAR COOLING SYSTEM for AIR 2015
HANDLING UNITS of GARMENT ROOMS’ AC SYSTEM

meridian of the point directly under the sun. The hour angle can be obtained from the
apparent solar time (AST) that is:

h=( AST −12 ) … … … … … .3 .7.3

Where,

AST is apparent solar time

Solar Altitude angle( α )

Altitude angle is defined as the angle in vertical plane between the sun’s rays and the
horizontal projection of the sun’s rays. The solar altitude angle is the angle between the
suns ray and a horizontal plane as shown on the following figure.

Figure 4.5 apparent daily path of the sun across the sky from sun rise to sun set

π
α +∅= … … … … … … … … … … … … … … … … … … …..4.2.2 a
2

sinα=cos ∅=sinL × sinδ+ cosLcosδcosh … … … … 4.2 .2 b

Where,

δ =¿ Is declination angle

h=¿ Is hour angle

L=¿Is the solar latitude angle, defined as the angle between a line from the Centre of the
earth to the site of interest and the equatorial plane?

G/HANNES T. And KINDALEM T. Page lxxi

 DESIGN of SOLAR COOLING SYSTEM for AIR 2015
HANDLING UNITS of GARMENT ROOMS’ AC SYSTEM

Zenith angle( θz )

Zenith angle is an angle between the sun’s rays and a line perpendicular to the horizontal
plane at point O. The solar altitude is related to the solar Zenith angle ( ∅ ) Rays and the
vertical. And it is given by the following mathematical expression.

Analysis:

Mathematical expression:

θ z=90° −α … … … … … … … … … … …..4.2.3 c

cosZ =sinlsinδ + coslcosδcosh

θ z=cos−1 ( sin Lsin δ +cos L cos δ cos h ) … … … … … … … … ..4.2.3 d

NB – Vl ues at north of the equator are positive and those south are negative

Solar Azimuth angle( Z )

Azimuth angle is the angle in the horizontal plane measured from south (northern
hemisphere) to the horizontal projection of the sun’s rays. The solar azimuth angle is the
angular displacement from south of the projection of beam radiation on the horizontal plane,
displacement east of south are negative and west of south are positive., westward is
designated as positive. Mathematical expression is as follows.

Analysis

Mathematical expression:

sinh × cosδ
sinZ=
cosα

Z=sin −1 ( sincosL cosα δ ) … … … … … … … … … ..4.2.4

Surface Azimuth angle ( Zs )

It is the angle between the normal to the surface from true south, west ward is designated as
Positive. Thus surface azimuth angle is in between -90°&90°depending on the solar azimuth
angle.

G/HANNES T. And KINDALEM T. Page lxxii

 DESIGN of SOLAR COOLING SYSTEM for AIR 2015
HANDLING UNITS of GARMENT ROOMS’ AC SYSTEM

If Z> 0° , Zs=90 °
If Z< 0° , Zs=−90°

Figure 4.6 azimuth and altitude for northern latitude

4.2.2 Intensity of Extraterritorial radiation

Besides to the total energy in the solar which solar constant it is useful so as to know the
spectral distribution of the extra-terrestrial radiation that is the radiation that would be
received in the absence of atmosphere. Solar radiation received on the surface at the limit of
the earth’s atmosphere and radiation measured on the plane normal to the radiation on the
Nthday of the year.

4.2.3 Extraterrestrial radiation on the horizontal plane( I ' )

At any point of time the extra-terrestrial radiation on the horizontal plane is given by

I ' =Icosθz … … … … … … … … … … … … … … … .4 .2.5 a

cosθz =cosLcosδ × h × sinlsinδ … … … … …..4.2.5 b

( N ×360 )
(
I =I '' × 1+ 0.033 cos
365 ) … … … … … …..4.2.5 c

Where

G/HANNES T. And KINDALEM T. Page lxxiii

 DESIGN of SOLAR COOLING SYSTEM for AIR 2015
HANDLING UNITS of GARMENT ROOMS’ AC SYSTEM

N is the day of the year1 ≤ N ≤ 360

I =¿Extraterrestrial solar radiation at normal incident

I ' =¿Extraterrestrial radiation on the horizontal plane

L=¿ Latitude angle

δ =¿ Inclination angle

h=¿ Hour angle

4.2.4 Daily extraterrestrial radiation on the horizontal surface( Ho )

24 ' ' N × 360
Ho=
π (
× I × 1+0.033 cos
365 )
× ( cosLcosδsinh +hs× sinlsinδ ) … … 4.2 .6

h s=−tan L tan δ … … … … … … … … … … … … … … … … … … … … … … … … … … 4.2.7

Where,

I =¿Mean solar constant

I '=¿= Extraterritorial radiation measured on the plane normal to the radiation on the N TH
day of the year.

Day length( n )

2 hs 2 −1
n= = cos (−tan L tan δ ) … … … … … … … … … … … … … … … … ..4.2.8
15 15

Solar energy flux constant:

Measurement indicated that the energy flux received from the sun outside the earth’s
atmosphere is constant. Since in December21 mean solar constant is maximum=1390w/m 2
and in June21 mean solar is minimum =1339w/m2 (maximum wave length in summer).

Then take mean constant value of I =1367 w /m².

4.2.5 Beam radiation ( I b)

Solar radiation received at the earth’s surface without change of direction i.e. in the line with
the sun is known as beam radiation or direct radiation.

G/HANNES T. And KINDALEM T. Page lxxiv

 DESIGN of SOLAR COOLING SYSTEM for AIR 2015
HANDLING UNITS of GARMENT ROOMS’ AC SYSTEM

Beam radiation tilt factor ( Rb )

For purposes of solar process design and performance calculation, it is often necessary to
calculate the hourly radiation on a tilted surface of a collector from measurement or
estimates of solar radiation on a horizontal surface. The most commonly available data are
total radiation for hours or days on the horizontal surface. Whereas the need is for beam and
diffuse radiation on the plane of a collector. The geometric factor R b, the ratio of beam
radiation on the tilted surface to that on a horizontal surface at any time, can be calculated
exactly by the appropriate use of equation.

Rb is the ratio of the beam radiation (or direct radiation) on a tilted surface (W/m2) to beam
radiation on a horizontal surface (W/m2) and it is given by:

I bt
Rb= … … … … … … … … … … … … … … … … … … … 4.2.9 e
Ib
Rb =√ ¿¿ ¿ ………………………………………………4.2.9f

Where,

Rb=¿ Beam radiation tilt factor

I bt =¿ Beam radiation on a tilted surface

I b=¿Beam radiation on a horizontal surface

4.2.6 Important parameters used for designing of parabolic trough solar

collector equipment

The parameters that are used for sizing of parabolic trough are listed in the form of table
below.

Table 4.3parameters of parabolic solar collector

Main parameters of parabolic trough

G/HANNES T. And KINDALEM T. Page lxxv

 DESIGN of SOLAR COOLING SYSTEM for AIR 2015
HANDLING UNITS of GARMENT ROOMS’ AC SYSTEM

-Aperture width(Wa) Focal length (f) and rim radius( Rr ¿

2f
Wa=4 × f × tan ( βr2 ) … … … … 4.2 .6 Rr =
1+ cos
βr
… … … … … … … …...4.2.1 7
2
Wa=C × π × D … … … … … … … 4.2 .7
Height of parabola ( Hp)
Aperture Area(A a)
Wa ²
Aa=( Wa−0.03 ) × L… … … 4.2.8 H P= … … … … … … … . 4.2 .18
16× f
Absorber area (Aabs) Optical efficiency (ηo )
Aab =π × D O × L… … … …..4.2. 9
ηo =× ρ × τ × α … … … … … … …..4.2.1 9
Length tube ( Lr )
Lr =Lc + allowance … … … 4.2.10
Thermal efficiency of the collector()
Length of parabolic trough(L)
ηth =Qc /Qs … … … … … … … … ….4 .2 .20
2L
W a= … 4.2 .11
φr φr φr φr U L F R × ( T i −T a )
2 2 2 (
sec + tan +ln sec +tan
2 )
ηth =F R ηO −
C ×Ib
… … . … 4.2.21

γ 1 Concentration ratio ( C )
sec = … … … … … … … … … … 4.2.12
2 γ
cos Aa
2 C= … … … … … … … … … … … 4.2.22
A ab
Diameter of cover tube( Dc ) Acceptance angle(θm )
Dc=D O +GAP … … … … … … 4.2 .13 DO =2× Rr ×sin Θm … … … … … 4.2 .23
Length of cover tube(Lcover)
Lct =Lr −gap … … … … … … 4.2 .14

Heat Transfer in the Receiver (Qd )

Q d =ṁ w∗C P∗( T E −T i) … … ..4.2.1 5

(Source of H.Pgarg, prakasasl, solar energy, principles and applications, university of

Calcutta, 2001, 2)

CHAPTER-FIVE

G/HANNES T. And KINDALEM T. Page lxxvi

 DESIGN of SOLAR COOLING SYSTEM for AIR 2015
HANDLING UNITS of GARMENT ROOMS’ AC SYSTEM

Design analysis
5.1Solar radiation data

The average daily solar radiation at a location in a given month, year extra is often sufficient
for basic system analysis. This data may be presented either as measured on horizontal or
measured with the measuring surface perpendicular to the solar radiation. Most radiation
data is measured from horizontal surface. Typical daily record of global and diffuse
radiation is measured on a clear day. To calculate the average day of the month ‘N’ first let
us determine the value of the date given in the table in appendix B-1 by using mean
statistical data

10.22+ 10.3+ 8.1+9+10+6.6+ 5+4 +7.2+9.55+11.1+ 9.4

Averagehour ( hr )=
12

100.47
average hour= =8.373
12

As we have seen in table-2, appendix-B since the average value of the month that we
calculated in three years is 8.373. It is approached to 8.1. Therefore; the month that we
selected for design consideration is March. Hence, in this design Mekelle has maximum
solar radiation recorded on March 8.373hr. Therefore, i=16 days

For this reason, from the above table the average day of the year is being calculated as

N=i+59

Substitute i=¿16days

N=16 +59=75 days

5.2Basic sun -earth angle calculation

Declination angle (δ)

360 × ( N +284 )
δ =23.45 ° sin
365

Where, N is average day of the year

1 ≤ N ≤ 365 , N =75

Using N value it is easy to calculate the value of the Declination angle (δ)

G/HANNES T. And KINDALEM T. Page lxxvii

 DESIGN of SOLAR COOLING SYSTEM for AIR 2015
HANDLING UNITS of GARMENT ROOMS’ AC SYSTEM

Substitute N=67.373 in the above equation

360 × ( 75+284 )
δ =23.45 ° sin =−2.42°
365

Hour angle( h )

h=( AST −12 ) ×15 °

Where, AST is apparent solar time taken to be 15:00 in which for calculation it is taken as
15:00. Thus taking this value to the above equation we have the value to be

h=( 15−12 )∗15° =45 °

Latitude (L)

Latitude is the angular location north or south of the equator, north positive -90°≤L≤90° or it
is the angle between the axis and the reflected beam at the focus of the parabola.

Altitude angle is defined as the angle in vertical plane between the sun’s rays and the
horizontal projection of the sun’s rays. This angle is being calculated by the following
mathematical analysis.

2h s 2 −1
= cos (−tan L tan δ )
15 15

But n & L are unknowns

Since mekelle is located in Ethiopia at13.48°N& 39.467°E, the angle for design
consideration is being equal to13.48°

Where, n=¿ number of days sun shine hours which is maximum

Maximum number of days sun shine hour (Day length)(n)

2
n= cos−1 (−tan −2.42 tan 13.48 )
15

Where,tan13.48=0.2397,tan−2.42=−0.042

Substitute these values in the above equation and it will be

2
n= tan −1 ( 0.042∗0.2397 )=12
15

G/HANNES T. And KINDALEM T. Page lxxviii

 DESIGN of SOLAR COOLING SYSTEM for AIR 2015
HANDLING UNITS of GARMENT ROOMS’ AC SYSTEM

Solar Altitude angle( α )

Solar altitude angle is an angle determined by the mathematical expression stated in

equation one &two above.

sinα=cos ∅=sinL × sinδ+ cosLcosδcosh

sinα=sin 13.48∗sin (−2.42 )+ cos 13.48 cos (−2.42 ) cos ( 45 )=42.6 °

ZENITH ANGLE( θz )

π
θz= −α =90 °−42.6 ° =47.38 °
2

Solar Azimuth angle( Z ) : solar azimuth angle is an angle that evaluated by the following
mathematical expression

Analysis

sinh × cosδ
sinZ=
cosα

cos(−2.42)∗sin 45
Z=sin−1 =sin−1 ( 0.93549 )=72.46 °
cos 42.6

Surface Azimuth angle ( Zs )

Surface azimuth angle is in between -90°&90°depending on the solar azimuth angle.

If θz> 0 ˚ , Zs=90

If θz< 0 ˚ , Zs=−90

Thus, from the above relation since the value of solar azimuth angle is positive which is
equals to 72.46°, thenZs=90°.

Hour angle in sun set( hs )

The hour angle in sun set is being calculated as

coshs=−tanLtanδ=−tan 13.48 tan (−2.42 )=89.4 °

Since the hour angle in the sun set is b/n−180 ° ≤ hs ≤ 180 ° , hs=89.41 ° it is therefore safe
and the latitude angle that we used for design consideration is the best.

G/HANNES T. And KINDALEM T. Page lxxix

 DESIGN of SOLAR COOLING SYSTEM for AIR 2015
HANDLING UNITS of GARMENT ROOMS’ AC SYSTEM

5.2.1 Monthly average daily solar radiation (H) & daily average hourly solar
radiation
The monthly average daily solar radiation (Ho): can be calculated by using average daily
radiation (Ho) and the cloudiness index (Kt) which is the ratio of monthly average daily
solar radiation on horizontal surface to the monthly average extra-terrestrial solar radiation.

H
Kt=
HO

24 360 ×75 89.41 π

HO=
π (
×1367 × 1+0.033 cos
365 )(
× cos 13.48 cos (−2.42 ) sin 89.41+
180
sin 13.48 sin (−2.42 ) )
W
H O =10538.26× 1.3175× 0.1=1076.4
m²

Where, the given and calculated values are given below

L=13.48 ° ,hs=89.41 ° ,formonthmarchN =75 days ,δ =−2.42 °

The value of cloudiness index, Kt and Hd /H can be found from the following figure.

Since the sun set hour angle hs equals to89.41, Hd /H can be determined from

Hd
Forh s< 81.4 ° , =1.0 .2832 Kt −2.5557 k t 2+ 0.8448 k t 3, forkt <0.722
H

hs >89.41° , Hd/ H=0.175 , forKt ≥ 0.722

Assumed that K t =0.999

Therefore;

Id
=0.17
H

Now we can calculate the monthly average daily solar radiation using K t =0.999

H=K t × H O

W
H=0.999× 1076.4
m2

W
H=1075.32
m²

G/HANNES T. And KINDALEM T. Page lxxx

 DESIGN of SOLAR COOLING SYSTEM for AIR 2015
HANDLING UNITS of GARMENT ROOMS’ AC SYSTEM

5.2.2Daily average solar radiation on horizontal surface( Ig )

The daily average radiation is the sum of daily average beam radiation and daily average
diffuse radiation. Daily average radiation reaching on the horizontal surface is given by

Ig=Ib+ Id

Now,Ib=Ibncosθz

Ig=Ibncosθz+ Id

But Id is unknown,

Where,

Id=¿Daily average diffuse radiation

W
I =¿Mean solar constant1367
m²

Ig=¿Daily average radiation

θz=¿ Zenith angle or incidence angle=72.46°

The ratio of monthly average daily radiation to daily average hourly radiation is given by:

Ig
Ri=
H

π cosh−coshs
Ri= ( a+ bcosh ) × ⌈ ⌉
24 2 π × hs
coshs( 360 )× sinhs

Where,

H=¿Monthly average daily radiation

Ig=¿Daily average hourly radiation

Id=¿ Daily average hourly diffuse radiation

( 91.44−60 )=0.67
a=0.409+0.5016 sin ( hs−60 )=0.409+0.5016 sin

b=0.6609−0.4767 sin ( hs−60 )=0.6609−0.4767 sin ( 91.4−60 ) =0.427

G/HANNES T. And KINDALEM T. Page lxxxi

 DESIGN of SOLAR COOLING SYSTEM for AIR 2015
HANDLING UNITS of GARMENT ROOMS’ AC SYSTEM

h=¿Hour angle=45°

hs=¿ Hour angle in sun set in radians

π cos 45−cos 89.41

Ri= ( 0.67+ 0.413 cos 45 ) × ⌈ ⌉ =5.32
24 π × 89.41
sin 89.41×( 180 )
× cos 89.41

Ig=H × Ri

w
Ig=1075.32 ×5.32
m2

kw
Ig=5720.72
m²

Since the daily average solar radiation which have been studied in Ethiopia is in between

kw
( 5−6 ) .
m ² day

Thus, the value of Ig which we calculated above is equals to5.72kw/m 2, so that this number
is true.

The ratio of daily average hourly diffuse radiation (hourly global diffuse radiation) to daily
average radiation is given by:

Id
Rd=
Ig

π cosh −coshs
Rd=
24
[ sinh−
2 πhs
(
360 )
coshs ]
π cos 45−cos 89.41
Rd=
24
[ sin 45−
( 2 π × 89.41 )
( 360 )
×cos 89.4 ]
=0.201

Id=Rd × Ig=0.093 ×5720.72=1149.89

kw
I d=1.14989
m2

5.2.3The daily average beam radiation

G/HANNES T. And KINDALEM T. Page lxxxii

 DESIGN of SOLAR COOLING SYSTEM for AIR 2015
HANDLING UNITS of GARMENT ROOMS’ AC SYSTEM

This is solar radiation received at the earth’s surface without change of direction i.e. in the
line with the sun. It is determined by the following mathematical expression

kw
I b=I g −I d =4.57083
m²

Angle of incidence in tilted surface( θt )

An angle of incidence is an azimuth angle in the tilted surface in which it is being

determined by the following mathematical expression

Analysis

cosθt sinδsin ( L−γ ) + cosδcos ( L−γ ) cosh

Rb = =
cosθz sinδsinL+ cosLcosδcosh

−1
θt =cos ( R b × cos θ Z )

But Rb &γ are unknown

In order to find out the value of θt first we have to determine what the beam radiation tilted
factor should be. This beam radiation tilted factor can be determined by the following
formula

Rb =√ ¿¿ ¿

Rb=1.189

θt =cos−1 ( 1.189∗cos 72.46 )=69

The slope angleγ is also determined by

cosθt =sinδsin ( L−γ )+ cosδcos ( L−γ ) cosh

cos θ t=sin δ [ sin L cos γ−cos Lsin γ ] +cos δ [ cos Lcos γ + sin L sin γ ]

cos 69=sin (−2.42 ) ×sin ( 13.48−γ ) +cos (−2.42 ) × cos ( 13.48−γ ) ×cos 45

0.389=−0.024336 cosγ +0.103376 sinγ + 0.6651cosγ−0.1637 sinγ

Using trigonometric identities

1=sin ² γ + cos ² γ

G/HANNES T. And KINDALEM T. Page lxxxiii

 DESIGN of SOLAR COOLING SYSTEM for AIR 2015
HANDLING UNITS of GARMENT ROOMS’ AC SYSTEM

sinγ=√ 1−cos ² γ

Substitute this equation in to the above equation and it will be

0.342=−0.024336 cosγ+ 0.103376 √ 1−cos ² γ +0.6651 cosγ−0.1637 √ 1−cos ² γ

[ 0.342=0.6401cosγ−0.060324 √1−cos ² γ ] ²

Assumed that, c=0.342, b=√ 1−cos ² γ , acosγ

[ c=0.6401 a−0.060324 b ] ²

c²= [0.6401a-0.060324b]²

c 2=0.41 a 2−0.039 ab+0.0364 b2

0.1164964=0.4017 a ²−0.048 ab+b ²

0.3981 cos ² γ−0.048× ( √1−cos ² γ ) × cosγ−0.1132=0

Using quadratic equation

Let,X =cosγ

−b ± √ b 2−4 ac
X=
2a

−0.048± √ 0.048−4 × ( 0.3981× (−.1132 ) )

X=
2× 0.3981

X =0.64278 ∨ X =−0.4887

Since the slope angle on the tilted surface is 0 ≤ γ ≤ 90 ° taking the X values 0.0.64278

γ =cos−1 X=50°

Where,

cos 67.1=0.389 ; sin−2.42=0.994 ; cos 13.48=0.972

cos 45=0.707; sin−2.42=−0.104 ; sin 13.48=0.233

θt =¿Angle of incidence in tilted surface

G/HANNES T. And KINDALEM T. Page lxxxiv

 DESIGN of SOLAR COOLING SYSTEM for AIR 2015
HANDLING UNITS of GARMENT ROOMS’ AC SYSTEM

θz=¿Angle of incidence on horizontal surface (zenith angle)

Rb=¿Tilted factor for beam radiation

L=¿ Latitude angle of the place of north or south of the equator, notes that north positive
and south negative

γ =¿ Slope angle on tilted surface

δ =¿ Declination angle of the sun (North positive and south negative)

h=¿ Solar hour angle from solar noon (Moring positive after noon negative)

5.2.4 Daily average solar radiation on tilted surface ( It )

Very often measuring instrument gives the values solar radiation falling on horizontal
surface but solar equipment (e.g. flat plat collector) for absorbing radiation is tilted at an
angle to horizontal. Therefore, it becomes necessary to calculate the flux which falls on a
tilted surface. This flux is the sum of beam radiation and diffuse radiation.

The flux that is falling on the tilted surface at any instant is the sum of beam radiation,
reflected radiation and diffuse radiation. It is given by

It=I b× Rb+ Id × Rd+ ( Ib+ Id ) × Rr

5.2.5 Daily average Beam radiation on tilted surface (DABRTS)

I bt
Rb =
Ib

kw
I bt =4570.83× 1.189=5.4347
m²

Where,

Ib=¿ A beam radiation on horizontal surface

Ibt=¿A beam radiation on tilted surface

θt =¿Angle of incidence on tilted surface

θz=¿Angle of incidence on horizontal surface (zenith angle)

Rb=¿Tilted factor for beam radiation

G/HANNES T. And KINDALEM T. Page lxxxv

 DESIGN of SOLAR COOLING SYSTEM for AIR 2015
HANDLING UNITS of GARMENT ROOMS’ AC SYSTEM

L=¿ Latitude angle of the place of north or south of the equator, notes that north positive
and south negative

γ =¿ Slope angle on tilted surface

δ =¿ Declination angle of the sun (North positive and south negative)

h=¿ Solar hour angle from solar noon (Moring positive after noon negative)

5.2.6 Daily average diffuse radiation( Id )

Diffuse radiation tilted factor: is the ratio of the diffuse radiation flux falling on the tilted
surface to that falling horizontal surface. This factor can be calculated as

Idt γ 1+cosγ
rd= =cos ²
Id 2 2

1+ cos 50.4
rd= =0.794
2

Reflected radiation( Rr )

1+ cosφ
Since is the radiation shape factor for tilted surface with respect to the sky. It
2

1−cosφ
follows that is the radiation shape factor with respect to surrounding ground.
2

Assumes that the reflection of the beam radiation and diffuse radiation falling on the ground
is diffuse and isotropic, and then the tilted factor of the reflection radiation is being given by

Rr=ρ × ( 1−cosγ
2 )=sin ²
γ
2

Rr=20 × ( 1−cos2 50.4 )=0.0236

Notes that one difficulty with this equation is that the value of the diffuse reflectivity ρis not
known, but the value around 20 is general expected value.

I T =I Bt + I Dt + ( I Bt + I Dt ) × Rr

I T =I b × Rb + I d × R d + ( I b + I d ) × Rr

G/HANNES T. And KINDALEM T. Page lxxxvi

 DESIGN of SOLAR COOLING SYSTEM for AIR 2015
HANDLING UNITS of GARMENT ROOMS’ AC SYSTEM

I T =4570.83 ×1.189+0.794 × 1149.89+ ( 4570.83+1149.89 ) × 0.0236

Kw
I T =6.048
m²

Therefore; the daily average flux in both tilted and horizontal surface respectively is

Kw
I T =6.048
m²

kw
Ig=5.7272
m²

5.3 Sizing of parabolic trough solar collector

5.3.1 Specification

Aperture area( A a) =ranging from1m2to 6m2(which is the most standard)

Expected inlet temperature (T I ) =25℃

Diameter of the receiver tube ( DO ) = ranging from 25mm to 50mm

Thickness of the receiver tube =3mm

Geometric concentration ratio of the receiver tube ranging from 10 to 80

(Source from solar energy and principle of solar thermal collector second edition,
SPSUKHATME in page 203)

Assumption

The heat transfer rate due to convection and conduction in the absorber is negligible
Analysis

Width of aperture¿)

From the diagram below it is noticed that

W a =4∗f ∗tan(Φr /2)

Where,

G/HANNES T. And KINDALEM T. Page lxxxvii

 DESIGN of SOLAR COOLING SYSTEM for AIR 2015
HANDLING UNITS of GARMENT ROOMS’ AC SYSTEM

W a =aperturewidt h
f =¿ focal length of the parabola
φ r=¿¿ rim angle of the parabola ranging from 70 ° to 120 °

Figure 5.1cross section of a parabolic trough with circular receiver

Y2 =4fx where, f=the focal distance (m)

For design analysis, take the rim angle =90o

90
W a =4 f tan =4 f tan 45=4 f , but f is unknown
2
The aperture width (Wa) is also calculated from the following equation

w a=C × π DO

W a =18 ×0.025 π=1.414 m

Length of the collector

Wa
L= ¿
2

Where,

C=¿The concentration ratio ranging from 10to 80 take the value of C = 18(assumption)

DO =¿ Diameters of the absorber tube ranging from 25 to 50mm take the values
DO =25 mm

G/HANNES T. And KINDALEM T. Page lxxxviii

 DESIGN of SOLAR COOLING SYSTEM for AIR 2015
HANDLING UNITS of GARMENT ROOMS’ AC SYSTEM

To get maximum length of the receiver ( L)

∅ r=¿Rim angle taking 90°

90 90
tan =1, sec =1.141
2 2

Substituting these values in the above equation and it will be

L=3 m

Length of receiver tube

In order to determine the length of the receiver which is also the length of the collector
trough plus some allowance is obtained from the total rate of heat transfer energy from the
trough in which the expected logarithmic mean temperature. But the logarithmic mean
temperature is unknown.

The length of the receiver tube is a little longer (10 percent) than the collector length. It is
being determined as

Lr =L+ 10 % × L=3000 mm+ 300 mm=3300 mm

Aperture area ( Aa )

The aperture area is an area that can be determined as

Aa =( W a −0.03 ) × L

Where,

W a =aperture width, DO= Outside diameter of the receiver tube

L=aperture length

Substitute these values and it will be

Aa =( 1.414−0.03 ) × 3 m=4.2 m 2

Absorber area

Aab =π D O L=0.025 × 3× π =0.23 m2

G/HANNES T. And KINDALEM T. Page lxxxix

 DESIGN of SOLAR COOLING SYSTEM for AIR 2015
HANDLING UNITS of GARMENT ROOMS’ AC SYSTEM

Insure that the concentration ratio is equals to18

Aa 4.2
C= = =18.0012
A ab 0.23

Therefore, our selection is safe.

Focal length ( H P ¿

∅r
W a =4 f tan
2

Substitute these values and it is easy to determine the value of focal length

1.414
f= =0.3535 m
4

Height of parabola

At any rim angle the height of the parabola can be calculated by the following formula

W a 1.414 ×1.414
H P= = =0.3535 m
16 f 16 ×0.3535

G/HANNES T. And KINDALEM T. Page xc

 DESIGN of SOLAR COOLING SYSTEM for AIR 2015
HANDLING UNITS of GARMENT ROOMS’ AC SYSTEM

Figure 5.2 rim angle diagram

Since the rim angle that we selected is equal to 90 degree the height of the parabola is being
the same as focal length of the parabola. As we have seen in the above figure as rim angle
increases the height of the parabola increases, but the focal length decreases and as focal
length increases, the shape of the parabola should be flattened.

Rim radius ( Rr )

At rim angle equal to 90°therim radius ( Rr ¿can be calculated by the following formula

2f 2 ×0.3535
Rr = = =0.59 m
φr 90
1+ cos 1+ cos
2 2

Where,90 /2=45 °

Parameters of tube

Diameter of the cover tube ( D glass)

The diameter of cover tube also called glass cover is calculated by the following expression:

The gap between the cover tube diameter and the absorber tube diameter is ranging from
1cm to2cm.

Dc=D O + gap, taking 1.2cm then the diameter of the cover tube is applied by the following
analysis

D glass=25 mm+12 mm=37 mm

The thickness of the cover glass is assumed to be 3mm

The internal diameter of the cover glass d i is then

D glass−3 mm=34 mm

Length of glass cover

The length of the cover plate is the length of the collector plus an allowance (1cmto 12mm)
which is common). Length of the parabolic trough is being calculated above which is not
necessary to calculate it a4 Length of the cover tube (L cover)

G/HANNES T. And KINDALEM T. Page xci

 DESIGN of SOLAR COOLING SYSTEM for AIR 2015
HANDLING UNITS of GARMENT ROOMS’ AC SYSTEM

Lcover =Lr +12 mm

Lcover =3300 mm+12 mm=3312mm

Concentration ratio (C ¿

The geometric concentration ratio is the ratio of affective aperture area to absorber area. It is
given by

Aa 4.1
C= = =18.02
A ab 0.23

Therefore, the concentration ratio that we had assumed in the above calculation is safe.

5.4Data collection and thermal cooling load calculation for garment building in
Quiha

5.4.1 Basic Information

5.4.1.1 Building Location

The Garment building considered in this study is situated in Tigray region , Quiha and
located at latitude and longitude of 13°29′N 39°38′E / 13.483°N 39.633°E at an elevation of
about 2,247 m (7,372 ft) above mean sea level.

5.4.1.2 Climate condition

In Quiha according to recent climate data, it has maximum average temperature of 29 0C and
average minimum temperature of 6.03 0C, and average relative humidity of 56 % with
annual average wind speed of 4.64m/s.

5.4.1.3Design condition

The amount of cooling that has to be accomplished to keep buildings comfortable depends
on the desired indoor conditions and on the outdoor conditions on a given day. These
conditions summer and winter are, respectively, called the “indoor design condition” and the
“outdoor design condition”.

For most of the industrial process, the recommended indoor temperature and relative
humidity are as follows

DBT – 22.78 0C to 26.11 0C, and RH – 50% for summer

G/HANNES T. And KINDALEM T. Page xcii

 DESIGN of SOLAR COOLING SYSTEM for AIR 2015
HANDLING UNITS of GARMENT ROOMS’ AC SYSTEM

DBT – 22.11 0C to 22.22 0C and RH – 20 to 30% for winter

(Source: ASHRAE FUNDAMENTAL HANDBOOK, 1999)

The cooling load of the GARMENT DEARTMENT is based on 23 0C dry bulb temperature
and 50% relative humidity indoor design conditions and the outdoor design is based on
32.440 DBT and relative humidity of 56%.

Data from Garment rooms

Other than the main room, there are seven offices inside of the Garment room. They are
found to the south east direction. These are:

1. Sample room 2.Satellite Store

3. Pattern & design room 4. Quality office

5. Marketing room 6.Production Area

7. General item store

5.4.1.4 Occupants

Table 5.1labourworkers and office of Garment rooms

SN Office Occupancy

Number of males Number of female

1 Main room 113 678

2 Sample room 4 2

3 Satellite Store 0 3

4 Pattern & design room 5 1

5 Quality office 2 0

6 Marketing room 4 3

7 Production Area 4 2

8 General item store 2 0

Table 5.2working lights

SN Rooms Lights

Light type Quantity Rated

G/HANNES T. And KINDALEM T. Page xciii

 DESIGN of SOLAR COOLING SYSTEM for AIR 2015
HANDLING UNITS of GARMENT ROOMS’ AC SYSTEM

power/unit
(watt)

1 Main room Single florescent 258 58

2 Sample room Double florescent 8 58

3 Satellite Store Double florescence 2 58

4 2 58 5 58

5 8 58 1 58

6 Marketing room Double florescent 4 58

7 Production Are Double florescent

8 General item store Double florescent

Table 5.3 Working machines

SN Name Quantity Rated power(w)

1 Single needle lockstitch machine 249 550

2 Double needle chain stitch machine 13 500

3 Double needle look stitch machine 34 520

4 5Toverlock machine 45 530

5 4Toverlock machine 120 550

6 Kinsey machine 10 450

7 Flat lock cylinder machine 75 500

8 Barr tacking machine 10 450

9 Button attach machine 12 450

10 Buttonhole machine 13 450

11 Welting pocket machine 2 520

12 2 needle feed off arm with front puller 6 400

13 3 needle feed off arm with front puller 15 420

14 Blind stitching machine 6 550

15 AMS machine 1 550

16 4 needle with band machine 17 550

17 Belt loop machine 1 500

G/HANNES T. And KINDALEM T. Page xciv

 DESIGN of SOLAR COOLING SYSTEM for AIR 2015
HANDLING UNITS of GARMENT ROOMS’ AC SYSTEM

Table 5.4sample rooms

SN. Name Quantity Rated power (w)

1 Over lock machine 7 750

2 Inter lock machine 8 650

3 Single needle 4 550

4 Computers 4 55

Table 5.5For Satellite Store, Pattern & design room, Quality office, Marketing
room, Production Area &General item store
SN Room

1 Satellite Store

2 Pattern & design room

3 Quality office

4 Marketing room

5 Production Area

6 General item store

Room size

V room=L∗W ∗H=(72∗118∗11)=93456 m3

Table5.6 Windows
SN Room Glass

Sun Quantity Length(m) Height(m) Total

facing Area(
m2)

1 Main room SE 113 0.6 0.5 33.9

NE 60 0.6 0.5 18

NW 75 0.6 0.5 22.5

2 Sample room SE 18 0.6 0.5 5.4

3 Satellite Store SE 6 0.6 0.5 1.8

G/HANNES T. And KINDALEM T. Page xcv

 DESIGN of SOLAR COOLING SYSTEM for AIR 2015
HANDLING UNITS of GARMENT ROOMS’ AC SYSTEM

4 Pattern & design room SE 7 0.6 0.5 2.1

5 Quality office SE 15 0.6 0.5 4.5

6 Production Area SE 12 0.6 0.5 3.6

7 Marketing room SE 6 0.6 0.5 1.8

8 General item store SE 18 0.6 0.5 5.4

Table 5.7 WALLS

SN Room Wall

Sun facing Length(m) Height(m) Area(m2)

1 Main room SE 118 8 944

NE 72 7.1+2.5 2 ( 2.5∗36 )
( 7.1∗72 ) + =601.2
2
NW 118 8 944

2 Sample SE 8 4 32
room

3 Satellite SE 5 4 20
Store

4 Pattern & SE 18 4 72
design room

5 Quality SE 11 4 44
office

6 Production SE 9 4 36
Area

7 Marketing SE 8 4 32
room

8 General item SE 20 4 80
store

Roof size

Area of south east roof= Length*Height =36.12*118=4262m2

Area of North West roof is equal to the area of the south east roof which is 4262m2.

Table 5.8Door
SN Direction door

G/HANNES T. And KINDALEM T. Page xcvi

 DESIGN of SOLAR COOLING SYSTEM for AIR 2015
HANDLING UNITS of GARMENT ROOMS’ AC SYSTEM

Small door Big door

Quantity L H A Quantity L H A

1 SE 2 1.2 2.1 5.04 2 4 4 32

2 NE - - - - 1 4 4 16

3 NW 1 1.2 2.1 2.52 1 4 4 16

5.4. 2Cooling load calculation

5.4.2.1 External cooling load for garment rooms

Heat gain through wall

Q wall = U × A × (CLTD )wallCorrected

Area of the wall through which solar transmits is equal to

Based on the ASRAE fundamental hand book table for CLTD values prepared for fixed
values of inside and outside temperatures for different type of wall and roofs due to this it
needs to correct then;

(CLTD)Corr.=(CLTD+LM)K + (25.550c-TR) + (TM – 29.40c)

 The value of K is =o.65 (white colour)

 The value of Tm will be

¿+Ti
T m=
2

29 ℃ +24 ℃
T m=
2

T m=26.5 ℃

TR=Ti=24 ℃

To find the correction CLTD we use the maximum solar time at the MAAGARMENT &
TEXTILE FACTORY from the metrological agency data it implies at 9:00pm or at 3:00
hours of the solar time and at the angle of 160N latitude.

Direction CLTD K LM T0(0C) Ti(0C) (CLTD)Corre

G/HANNES T. And KINDALEM T. Page xcvii

 DESIGN of SOLAR COOLING SYSTEM for AIR 2015
HANDLING UNITS of GARMENT ROOMS’ AC SYSTEM

SE 16 0.65 -5 29 24 5.8

NE 12 0.65 4 29 24 9.05

NW 7 0.65 3 29 24 5.15

WALL Construction material – hollow block concrete

R=0.18m2K/W, U = 5.56W/m2K

Where,
U- Is overall heat transfer coefficient
R- The resistance of the material
Heat gain through the wall of the main room

 For the south east direction

Area of the wall, A wall heat transferred through it is calculated as

A wall =A total ,wall −A Glass− A Offices− A door =(944−9.3−316−37.05)m 2=581.65 m 2

Q N =U × A ×(CLTD)wall Corr .=5.56 W /m 2 K∗581.65 m2∗5.8 K

Q N =18,757.0492

For the north east direction

Area of the wall, A wall heat transferred through it is calculated as

A wall=A total ,wall −A Glass− A door ¿( 601.2−18−16) m ²=567.2 m ²

Q N¿ U∗A∗(CLTD)wallCorr. ¿ 5.56 W /m 2 K∗567.2m ²∗9.05 K

QN¿ 29.002354 KW for the North West direction

Area of the wall, A wall heat transferred through it is calculated as

A wall=A total ,wall −A Glass− A door ¿( 944−22.5−16)m² ¿ 905.5 m ²

Q N =U × A ×(CLTD)wall Corr .

Q N =5.56 W /m² K ×905.5 m 2× 5.15 K

Q N =25.925 O 89 KW

Heat gain through the wall of the offices

G/HANNES T. And KINDALEM T. Page xcviii

 DESIGN of SOLAR COOLING SYSTEM for AIR 2015
HANDLING UNITS of GARMENT ROOMS’ AC SYSTEM

The offices are found inside of the main room to south east direction. The heat gain by these
offices is only through south east wall direction.

I. For sample room

Area of the wall, A wall heat transferred through is:

A wall=A Total ,wall− A Glass=( 32−5.4)m²=26.8 m ²

QN¿ U∗A∗(CLTD) wall Corr . =5.56W/m2K*26.8m2*5.8K

QN¿ 0.86425 KW
II. For satellite store

Area of the wall, A wall heat transferred through it is:

A wall=A Total ,wall − A Glass ¿( 20−1.8)m²=18.2 m2

QN¿ U × A ×(CLTD)wallCorr .

5.56 W
Q N= 2
× 18.2m 2 × 5.8 K ¿ 0.58914 KW For pattern &design room
m K

Area of the wall, A wall heat transferred through it is:

A wall=A Total ,wall − A Glass ¿(72−2.1) m ², A wall=69.9 m²

Q N =U × A ×(CLTD)wall Corr ¿ 5.56 W /m ² K∗69.9 m ²∗5.8 ¿ 2.25414 W

III. For quality office

Area of the wall, A wall heat transferred through it is:

A wall=A Total ,wall − A Glass

A wall=( 44−4.5)m²=39.5 m²

5.56 W
Q N =U∗A∗(CLTD )Wallcorr = ∗39.5 m 2∗5.8 K
m2 K

Q N =1.208 KW

IV. For production area

G/HANNES T. And KINDALEM T. Page xcix

 DESIGN of SOLAR COOLING SYSTEM for AIR 2015
HANDLING UNITS of GARMENT ROOMS’ AC SYSTEM

Area of the wall, A wall heat transferred through it is:

A wall=A Total ,wall − A Glass

¿(36−3.6)m²=32.4 m 2

Q N=U∗A∗(CLTD)wall Corr . =5.56W /m2 K∗32.4 m2∗5.8 K

Q N =1.044 .83 KW

V. For marketing room

Area of the wall, A wall heat transferred through it is:

A wall=A Total ,wall− A Glass=( 32−1.8)

A wall =30.2m2

Q N =U × A × ¿

Q N =0.9739 KW

VI. For general item room

Area of the wall, A wall heat transferred through it is:

A wall =A Total ,wall− A Glass=( 80−5.4)m ²=74.6 m 2

w
Q N=U × A ×(CLTD)wall Corr . =5.56 × 74.6 m² ×5.8 k=2.4057 KW
m²k

Total heat gain due to walls is calculated by summing up these which we have been
determined above,

QTotal ,wall=83.62 KW

Heat gain through glasses

1. Conductive

Q glass conductive = U * A * (CLTD) glass Corrected

 Material for windows are aluminium and glazing 4 mm clear glass from the
Architectural plan of the building

G/HANNES T. And KINDALEM T. Page c

 DESIGN of SOLAR COOLING SYSTEM for AIR 2015
HANDLING UNITS of GARMENT ROOMS’ AC SYSTEM

w
 The U-factor for aluminium window portable at 4 mm thickness glass is 7.24
m2 k
Source from ASRAE fundamental 1997, table 34, page 28.49 the conduction value
through glass will be
Solar time, h=15hrs and CLTD (0c) =8

Then,

Q glassconduction=U × A ×CLTDglass Corr .

(CLTD)Corr. =CLTD + (25.550c-TR) + (TM – 29.40c)................. (3.2)

(CLTD)glass Corr . =(CLTD) glass−1.35

(CLTD)glass Corr .=8 – 1.35
(CLTD)glass Corr . =6.65 K

Table 5.9Heat gain through glasses

SN Room Sun facing U(W/m2k) CLTDcorr Area(m2) QS(W)

1 Main room SE 7.24 6.65 33.9 1632.15

NE 7.24 6.65 18 866.63

NW 7.24 6.65 22.5 1083.3

2 Sample SE 7.24 6.65 5.4 259.98

room

3 Satellite SE 7.24 6.65 1.8 86.66

Store

4 Pattern & SE 7.24 6.65 2.1 101

design room

5 Quality SE 7.24 6.65 4.5 216.66

office

6 Production SE 7.24 6.65 3.6 173.3

Area

7 Marketing SE 7.24 6.65 1.8 86.66

room

8 General item SE 7.24 6.65 5.4 260

store

G/HANNES T. And KINDALEM T. Page ci

 DESIGN of SOLAR COOLING SYSTEM for AIR 2015
HANDLING UNITS of GARMENT ROOMS’ AC SYSTEM

Total heat gain through window glasses due to conduction,

Q Total ,conduction=4.80 KW
1. Solar Transmission

Q glass solar=A × SC × SCL=A × SHGFmax × SC

Table 3.10 Solar Transmission

Type of glass Thickness SC

No indoor shading Roller Shade light

dark

Single glass regular sheet 4 mm 0.25

1.00 0.59

w
 SHGF max = maximum solar heat gain factor for sun light glass on May at 150N
m2
latitude.

Date Solar time w

(SHGH) max
m2
SE NE NW

May 21 15:00am at noon 146 681 74

Q glass solar= A × SC∗SCL=A × SHGFmax × SC

SN Room Sun SHGF max SC Area(m2) QS

facing

1 Main room SE 146 1 33.9 4949.4

NE 681 1 18 12258

NW 74 1 22.5 1665

2 Sample room SE 146 1 5.4 788.4

3 Satellite Store SE 146 1 1.8 262.8

4 Pattern & design SE 146 1 2.1 306.6

room

5 Quality office SE 146 1 4.5 657

6 Production Area SE 146 1 3.6 525.6

G/HANNES T. And KINDALEM T. Page cii

 DESIGN of SOLAR COOLING SYSTEM for AIR 2015
HANDLING UNITS of GARMENT ROOMS’ AC SYSTEM

7 Marketing room SE 146 1 1.8 262.8

8 General item store SE 146 1 5.4 788.4

Total heat gain through window glasses due to solar transmission,

Q Total ,solartrans . =22.5 KW

Total heat gain through window glasses,

QTotal , glass=Q Total ,conduction+ QTotal, solartrans .

Q Total , glass=27.3 KW

Heat gain through doors

The offices are found inside of the main room. So the heat gain through the doors is
negligible. But we have to calculate the heat gain through doors for the main room.

Q S=U × A × ( CLTD )corr .

The overall heat transfer coefficient U for steel is, U= 1.02w/m2, R=0.98m2oc/w

Table 5.11Heat gain through doors

Direction Area(m2) U( w/m2oc) CLTDCorr ( oC ) QS (W )

SE 37.04 1.02 5.8 219.13

NE 16 1.02 9.05 147.7

NW 18.52 1.O2 5.15 97.3

Total heat gain through doors,

QTotal ,door =0.50 KW

Heat gain through roofs

Q S =U × Ar × CLTDcorr

CLTDcorr =CLTD× ( 25.5−T R ) +(T m −29.5)

CLTDcorr =CLTD−1.35 ℃ , at solar time= 15:MA

G/HANNES T. And KINDALEM T. Page ciii

 DESIGN of SOLAR COOLING SYSTEM for AIR 2015
HANDLING UNITS of GARMENT ROOMS’ AC SYSTEM

T0(0C)= 29, CLTD=23

( CLTD ) Corr .=21.65℃

The overall heat transfer coefficient U for steel is

U =1.02 w/m ²℃

W
Q S ,roof =8524 m 2∗1.02 ∗21.65 ℃
m 2 0c

Q S ,roof =188.235 KW

5.4.2.2 Internal Cooling Loads

a) Heat gain by occupants

Table 5.12Place, NO of people,

Place No. of people SHG(W) LHG(W) QS(W) QL(W)

Main room 440 110 185 48400 81400

Sample room 6 75 55 450 330

Satellite store 3 75 55 225 225

Pattern & design room 6 75 55 450 330

Quality office 2 75 55 150 110

Production area 7 75 55 525 385

Marketing room 6 75 55 450 330

General item room 2 75 55 150 110

Total sensible heat gain due to occupants,

QTotal ,sensible ,occu =50.8 KW

Total latent heat gain due to occupants,

Q Total ,latent ,occu =83.22 KW

b) Heat Gain from Light

Qlight = Total wattage of light * Use factor * Allowance factor *No of light

G/HANNES T. And KINDALEM T. Page civ

 DESIGN of SOLAR COOLING SYSTEM for AIR 2015
HANDLING UNITS of GARMENT ROOMS’ AC SYSTEM

The use factor is the ratio of actual wattage in use to installed wattage. Its value depends
upon the type of use to which room is put. In case of residences, commercial stores and
shops, its value is usually taken as unity, whereas for industrial workshops it is taken below
0.5. The allowance factor is generally used in the case of fluorescent light to allow for the
power used by the ballast. Its value is taken as 1.2.

Table 5.13Rooms, lights

Room Light type NO of light Wattage Use Allowan Q light
factor ce
of light factor (watt)
(watt)

Main room Single florescent 258 58 1 1.2 18026.4

Sample Double florescent 8 58 1 1.2 1113.6

room

Satellite Double 2 58 1 1.2 278.4

Store florescence

Pattern & Double florescent 5 58 1 1.2 696

design room

Quality Double florescent 1 58 1 1.2 139

office

Marketing Double florescent 4 58 1 1.2 556.8

room

Production Double florescent 2 58 1 1.2 278.4

Area

General item Double florescent 8 58 1 1.2 1136

store

Total heat gain due to light,

QTotal ,light =22.224 KW

c) Heat gain through appliance

Q Sensible=Q ¿ × Fu × F r ×(CLF )

Q Latent =Q¿ × F u

For main room

G/HANNES T. And KINDALEM T. Page cv

 DESIGN of SOLAR COOLING SYSTEM for AIR 2015
HANDLING UNITS of GARMENT ROOMS’ AC SYSTEM

Table 5.14main rooms

Name Quantity FU FR Q ¿( Q S (W ) Q L (W )
w)

Single needle lockstitch machine 249 0.34 0.14 550 6518.8 46563

Double needle chain stitch 13 0.41 0.33 500 879.5 2665

machine

Double needle look stitch 34 0.65 0.20 520 2298 11492

machine

5Toverlock machine 45 0.07 0.40 530 667.8 1670

4Toverlock machine 120 0.83 0.37 550 20268 54780

Kinsey machine 10 0.43 0.29 450 561 1935

Flat lock cylinder machine 75 0.57 0.24 500 513 21375

Barr tacking machine 10 0.22 0.12 450 118.8 990

Button attach machine 12 0.69 0.44 450 1639 3726

Buttonhole machine 13 0.45 0.23 450 605.5 2632.5

Welting pocket machine 2 0.56 0.12 520 70 582.4

2 needle feed off arm with front 6 0.50 0.45 400 540 1200
puller

3 needle feed off arm with front 15 0.78 0.37 420 1818.2 4914
puller

Blind stitching machine 6 0.23 0.23 55 174.6 759

0

AMS machine 1 0.79 0.44 55 191.18 4345

0

4 needle waist band machine 17 0.67 0.49 55 3069.6 6264.5

0

Belt loop machine 1 0.45 0.34 50 77 225

0

Sample room

Table 5.15Sample room

Name Quantity FU FR Q ¿ (W ) Q S (W ) Q L (W )

Over lock machine 7 0.25 0.43 750 564.4 1312.5

Inter lock machine 8 0.41 0.11 650 234.5 2132

G/HANNES T. And KINDALEM T. Page cvi

 DESIGN of SOLAR COOLING SYSTEM for AIR 2015
HANDLING UNITS of GARMENT ROOMS’ AC SYSTEM

Single needle 4 0.80 0.23 550 404.8 1760

Computers 4 0.50 0.27 55 30 110

Room Computers

Quantity FU FR Q ¿ (w) Q S (W ) Q L (W )

Satellite Store 0 0.50 0.27 0 0 0

Pattern & design room 3 0.50 0.27 55 22.28 82.5

Quality office 3 0.50 0.27 55 22.28 82.5

Marketing room 5 0.50 0.27 55 37.13 137.5

Production Area 6 0.50 0.27 55 44.55 165

General item store 1 0.50 0.27 55 7.43 27.5

Total sensible heat gain due to appliance,

Q Total ,sensible ,appl =47.38 kw

Total latent heat gain due to appliance

QTotal ,latent ,appl =172 kw

d) Heat gain due to ventilation of air

Ventilation air is the amount of outdoor air required to maintain indoor air quality for the
occupants and make up for air leaving the space due to equipment exhaust, infiltration and
pressurization.

Q sensible=1.08∗CFM∗(T o−T i)

Q Total=4.5 ×CFM ×( H O −H i)

Where:

ACH∗V m 3
CFM =
3600 sec

ACH= is varies about 0.2 to loosely constructed housing 2.0. We select 2 for our design.

G/HANNES T. And KINDALEM T. Page cvii

 DESIGN of SOLAR COOLING SYSTEM for AIR 2015
HANDLING UNITS of GARMENT ROOMS’ AC SYSTEM

ACH∗V m 3 2∗93456 m 3 m3
CFM = = =52.0
3600 sec 3600 sec sec

∆W = humidity ratio of indoor air - humidity ratio of outdoor air or we can get its value by
using psychometric chart.

From psychometric chart:

At Ti = 24 0c and at 50% RH, w i= 0.0094

At To = 29 0c and at 56% RH, w o= 0.0136

Therefore,

m3
Q sensible =1.08∗52 ∗(29−24 )° k
sec

Q sensible =0.280 kw

m3 (
Q sensible =4840∗52 ∗ 0.0136−0.0094 )
sec

Qsensible =1.057 KW

e) Heat gain due to infiltration

The sensible heat transfer rate due to infiltration is given by

Q S =ρairC ×C P × ∆ T

Where;

Kg Kg
ρair =air density ( 3
)=1.205 3
m m

m3
CFM =52.0
sec

KJ
C Pa= specific heat of air¿) = 1.005
Kg° K

∆ T =¿ Indoor temperature – outdoor temperature difference (0K)

G/HANNES T. And KINDALEM T. Page cviii

 DESIGN of SOLAR COOLING SYSTEM for AIR 2015
HANDLING UNITS of GARMENT ROOMS’ AC SYSTEM

Kg m3 KJ
Therefore, Q S =1.205 3
52.0 × 1.005 × 5 0 K ¿ 266.526 KW
m sec Kg

The latent heat due to infiltration is given (Q Lti ¿ by;

Q Lti= AFM × h fg × ∆W

J J
Where; h fg= latent heat of vapor at appropriate air temperature about 2.34 * 10 6 .
Kg Kg

m3
AFM=air flow rate∈
s

Q ¿ 511.056 KW
Therefore; L=52
m3 6
∗2.34∗10 ∗( 0.0136−0.0094 )
Sec

Table 5.16Table: summary of cooling load calculation

Summary of sensible heat( Q S ) and Latent heat ( Q ¿ )

SN. Load source Q S ( KW ) Q ¿ ( KW )

1 Walls 83.62 -

2 Window glasses 27.3 -

3 Doors 0.5 -

4 Roofs 188.24 -

5 Occupancy 50.8 83.22

6 Light 22.224 -

7 Appliances 47.38 172

8 Ventilation 0.28 1.057

9 Infiltration 266.526 511.056

10 Sub total 682.87 767.3

11 Total 1350

5.4.3 Other thermal analyses

5.4.3.1Working fluid for absorption refrigeration systems

G/HANNES T. And KINDALEM T. Page cix

 DESIGN of SOLAR COOLING SYSTEM for AIR 2015
HANDLING UNITS of GARMENT ROOMS’ AC SYSTEM

Performance of absorption refrigeration systems is critically dependent on the chemical and

thermodynamic properties of the working fluid the mixture should be chemically stable,
non-toxic and non-explosive.

 In addition to these requirements, the following characteristics are desirable.

 The elevation of boiling (the difference in boiling point between the pure refrigerant
and the mixture at the same pressure) should be as large as possible. Refrigerant
should have high heat of vaporization and high concentration within the absorbent in
order to maintain low circulation rate between the generator and the absorber per
unit of cooling capacity.
 Transport properties that influence heat and mass transfer, e.g., viscosity, thermal
conductivity and diffusion coefficient should be favorable.
 Both refrigerant and absorbent should be non-corrosive, environmental friendly and
low-cost.

Governing equations

The governing equations for the complete absorption refrigeration cycle are given by
examining the balances of mass, and energy for the different components in the cycle.

A thermodynamic simulation of a solar absorption refrigeration cycle has been carried out.
The binary mixture considered in the present equation is H2O– NH3 (water ammonia). This
simulation was performed in order to investigate the effect that the generator temperature
has over COP and mass flux on a single absorption refrigeration system that uses solar
energy as a primary source.

A typical single-effect absorption refrigeration cycle consists of four basic components, an

evaporator, an absorber, a generator and a condenser. The cooling cycle starts at the
evaporator, where liquefied refrigerant boils and takes some heat away with it from the
evaporator, which produces the “cold” desired in the refrigerated space. The refrigerant
vapour releases its latent heat as it is absorbed by a liquid absorbent in the absorber.

The flow in the pipes is assumed one- dimensional and no diffusion of heat occurs in the
flow direction. In addition, there is no heat loss from generator to the surroundings nor heat
gain by the evaporator from the surroundings and the expansion process in the valve is
assumed to occur at constant enthalpy.

G/HANNES T. And KINDALEM T. Page cx

 DESIGN of SOLAR COOLING SYSTEM for AIR 2015
HANDLING UNITS of GARMENT ROOMS’ AC SYSTEM

In actual air condition, (working fluid like ammonia-water, R12, R2) operating at condenser
temperature of 50oc evaporator temperature of 25oc, absorber temperature of 40oc.

These temperature selections are being used for getting good coefficient of performance.
Heat rejection at this temperature is approximately1.25 to1.35

State 1: exit from generator and inlet to the condenser

Generator is the distillation of vapour from the solution leaving the poor solution for
recycling. The cooling must be done in absorber to remove latent heat of refrigerant.

Notes that Ammonia which is used as a refrigerant in the single effective absorption
refrigeration system is, changed in to dry vapour at a temperature of 90℃ which is known
as super heated vapour.

Super-heated ammonia

T 1=90 ℃ P1 =P sat (Tc =50 ℃ )=20.33 .̄ from appendix B-5,using single interpolation, h 1
can be

50℃ −90 ℃ 1651−h1

=
50℃ −100 1651−4503

h1 =3933 KJ /kg v 1=0.118 mᶾ / kg

State 2: exit from condenser and inlet to expansion valve

T 2=50 ℃ pC =20.33 ¯¿ h f 3=495. 4 KJ /kg , v f =0.00177 m3/kg

kJ
h g=1050 , v =0.066 m3 /kg
Kg g

State3: exit from expansion valve and to evaporator

T3=5℃ p3=5.17 bar

h3=548.6 KJ/kg, v3=0.00158 m3/kg

State 4: exit from evaporator and inlet to absorber

T 4=25 ℃ P5=10.031 ,̄ hf 4=465.4 kJ /kg

h g 4 =2345.6 KJ/kg v g =0.128 m3/kg v f =0.00166 m3 /kg

G/HANNES T. And KINDALEM T. Page cxi

 DESIGN of SOLAR COOLING SYSTEM for AIR 2015
HANDLING UNITS of GARMENT ROOMS’ AC SYSTEM

State 5: exit from absorber and inlet to solution pump

T 5=40 ℃ P5=10.031 ¯¿

State 6: exiting from solution pump and inlet to HEX

State8: Exist from generator and inlet to HXT

kJ
h8 f =376.92 KJ / kg , h8 g=2660.1 KJ / kg , h fg =2282.2
kg

P8=P sat (T =90 ℃)=7.014bar

Energy balance

Heat cannot be destroyed or lost. However, it can be transferred from one body or substance
to another or to another form of energy. Since heat is not in itself a substance, it can best be
considered in relation to its effect on substances or bodies. When a body or substance is
stated to be cold, the heat that it contains is less concentrated or less intense than the heat in
some warmer body or substance used for comparison.

Energy balance and mass balance analysis

At the evaporator

Taking cooling (refrigerating) capacity of 13506kw that has been calculated in the cooling
load analysis.

Energy balance

Given, QL=1350KW

Q L= ṁ 4 ( h4 −h3 )

QL kg
ṁ4 = =0.39
hg 4 −h3 s

Mass balance

Mass flow rate of the refrigerant ammonia across the cycle is

ṁ 4 =ṁ 1=ṁ2 =ṁ 3=0.39 Kg/s

G/HANNES T. And KINDALEM T. Page cxii

 DESIGN of SOLAR COOLING SYSTEM for AIR 2015
HANDLING UNITS of GARMENT ROOMS’ AC SYSTEM

The volume flow rate of ammonia is being calculated as

v NH
˙ 3= ṁ 4 × v 4 =0.39 ×0.128=0.051 mᶾ / s

 Exit from absorber

At the absorber TO=40Oc and Pa=10.046bar, rich solution concentration ratio=0.34

At the generator TO=90Oc and p g=20.33bar, concentration ratio of ammonia vapour leaving
from generator at 90 and 20.33bar is 0.63

The poor solution concentration ratio of ammonia at saturated liquid at pressure =20.33bar
and TO=90Oc is 0.2

(Source: refrigeration and air conditioning 2ndedition page 330)

From total mass balance:

Mass of refrigerant (m) + mass of weak solution( ṁws )= mass of strong solution¿)

ṁ ss=ṁ+ ṁws

Quality of rich solution ( f )

The quality of rich solution is determined by

F ξ −ξ 0.63−0.2
f= = V L= =3.07 ≈ 3
ṁNH ξ a−ξ L 0.34−0.2
3

Where,

F=¿Mass handled by the pump

f =¿Fraction factor absorption

Quality of weak solution ()

F
¿ −1=f −1=3.0−1=2.0
ṁNH
3

Mass of strong and weak solution

In order to calculate mass of weak and strong solution we should first determine circulation
ratio(y).

G/HANNES T. And KINDALEM T. Page cxiii

 DESIGN of SOLAR COOLING SYSTEM for AIR 2015
HANDLING UNITS of GARMENT ROOMS’ AC SYSTEM

❑ws ❑L 0.2
y= = = =0.465
❑ ss−❑ws ❑V −❑L 0.63−0.2

Where,

❑ws=mass fraction of weak solution

❑ss= mass fraction of strong solution

y=circulation ratio

Mass of weak solution is then calculated by

kg
ṁ ws = y × ṁNH =0.465 ×0.39=0.181
3
s

Mass of strong solution is analyzed by

kg
ṁ ss =ṁ+ ṁws =0.39+0.181=0.571
s

Mass of water (ṁ w ¿

Mass of water is computed by

ṁ w =λ ṁ NH =0.78 Kg/ S
3

Exist from absorber and inlet to solution pump

Assumed that work done in solution pump is negligible compared to heat addition to the
generator

Mass balance

But the total mass flow rate which can be pumped or pressurized to the generator through
heat exchanger is equal to

ṁ ss =ṁ 5=0.5372kg /s

Exist from solution pump and inlet to heat exchanger

The liquid-liquid heat exchanger is one type heat transfer equipment in which heat is
transferred to the liquid aqua ammonia the temperature ranging from 50 oc to70oc with an

G/HANNES T. And KINDALEM T. Page cxiv

 DESIGN of SOLAR COOLING SYSTEM for AIR 2015
HANDLING UNITS of GARMENT ROOMS’ AC SYSTEM

average TO of 64oc.[Source from refrigerant table and air conditioning data, revised second
edition CP.KOTHADARRMAN]. From saturated table of R- 717(Ammonia)

At TO=64OC using interpolation method

(60 ℃−64 ℃) ( 1636.8−h7 )

=
( 60 ℃ −65℃ ) ( 1636.8−1638.1 )

h7¿ 1637.84 kg /s , P7=28.23bar, hf=349KJ/kg

Mass balance

ṁ5=ṁ6= ṁ7 =0.5372 kg/ s

Exist from (heat exchanger) and inlet to generator

The mass can be determined by

kg
ṁ 7= ṁ8 + ṁ 1 , ṁ8 =ṁ7 −ṁ 1=0.5372−0.39=0.1472
s

Where, ṁ 8= ṁ9 =ṁ10 =0.1472 kg/s

ṁ7= ṁ6 =ṁ5 =0.5372 kg/ s , ṁ1=ṁ2=ṁ3=ṁ4 =0.9 kg /s

Energy balance

Heat input to the generator is given by

Q g=ṁ NH 3 × h1+ y ṁ NH h8−ṁ NH (1+ y)h7

3 3

Q̇ g=0.39 kg /s∗3933 kj/ kg+ 0.465∗0.39∗2282.27 kj /kg−(0.39∗1.465∗1537.84 kJ /kg)

Q g=941.14 kJ / s

Coefficient of performance (COP)

Cooling load on theevaporator 1450

COP= = =1.54
heat addtion∈the generator 941.14

Given

Inlet temperature T i=25 ℃

G/HANNES T. And KINDALEM T. Page cxv

 DESIGN of SOLAR COOLING SYSTEM for AIR 2015
HANDLING UNITS of GARMENT ROOMS’ AC SYSTEM

Specific heat capacity of water C PW =4.195 kJ /kg

Solar thermal energy demand (Q d ¿

Q d =ṁ W C P ∆ T =ṁW C P ¿

Qd
Q g= +Qd … … … … … … … … … … .5.3 .4
η th

Where,

Q d =¿ The use full amount of solar thermal energy collected by the trough

T E =¿Outlet temperature of the heat transferring fluid

T i= inlet temperature of the heat transferring fluid=25oc

ṁ=¿ Mass flow rate of heat transferring fluid=0.1023kg/s

ηth =thermal efficiency

The energy demand is determined by

The important aspect in analyzing the solar collector is its efficiency. Basically the
thermal efficiency of any solar thermal collector is expressed as

Qd
ηth =
QS

Where,Q d =energy demand collected by the collector

Q s =¿Amount of solar radiation from the sun

QS =I b × A a ×ηO

Where,

I b=¿ Beam solar irradiation

Aa = aperture area in m2

ηo =optical efficiency

The optical efficiency contains complex parameters such as reflectivity, absorption,

G/HANNES T. And KINDALEM T. Page cxvi

 DESIGN of SOLAR COOLING SYSTEM for AIR 2015
HANDLING UNITS of GARMENT ROOMS’ AC SYSTEM

transmission and spillage of the mirror, the glass envelope and the absorber tube. For
aluminium reflective surface field test shows that the optical efficiency is ranging from
45 %to 70% .Taking the minimum assumed optic value 45% to calculate the amount of
energy which absorbed by receiver tube

γ 1 = intercept factor = 0.95,τ = Transmittance of glass cover = 0.93, 𝛼 = Absorbance of

absorber plate=0.96 , ρ=reflectance loss=0.85

ηO =γ 1 × ρ× τ × α=0.95× 0.93 ×0.96 ×0.85=72 %

Now, the thermal efficiency is determined by

F RU l ṁ C −πF U L L D O
ηth =F R ηO −
C Ib
( T i−T a ) , F R= w Pw 1−exp
π LD O U L ( (
ṁ w C P ))
1 1
F= = =o .76
1 D 1 0.025
Ul
[ − O
U l Di hf ] 1.1452 [ +
1.1452 0.02∗2000 ¿
¿ ]
Thus, having these values the heat removal factor is computed as

0.78∗4195 −π ×0.76 ×1.1452 ×3 × 0.025

FR=
π∗0.025∗1.1452∗3
1−exp
[ (
0.89 × 4195 )]
F R =1590∗[ 1−exp−0.00055 ] =1590 ( 1−0.99999 )=0.87

Where,

CP=specific heat capacity of heat transferring fluid (water)= 4.195KJ/kgoc

ṁ w = mass flow rate of the heat transferring fluid (water) = 0.89kg/s

Ta= ambient temperature=26Oc

Ti= Inlet temperature of heat transferring fluid=25Oc

Ul= over all heat loss coefficient for blackened steel pipe=1.1452w/m2oc

C= geometric concentration ratio =18

Ib = intensity of beam radiation=

G/HANNES T. And KINDALEM T. Page cxvii

 DESIGN of SOLAR COOLING SYSTEM for AIR 2015
HANDLING UNITS of GARMENT ROOMS’ AC SYSTEM

hf= coefficient of convective heat transferring fluid(water) ranging from 50w/m 2Oc-
20000w/m2oc

DO= outside diameter of the absorber tube =25mm,

Di= inside diameter of absorber tube=DO- Thickness=25-3=22mm

Thus, having these values thermal efficiency will be computed as

F R U l [ T i−T a ] 0.87∗1.1452 ( 25−26 )

ηth =F R ηO − =0.87∗0.72− =0.63=63 %
C Ib 18∗4570.83

Thus having this the useful energy which is collected by the absorber tube is computed as

Q g ×ηth
Qd = =394 kw /s
1+ηth

Having this value the change of temperature is computed as

Qd
∆T= =111℃
ṁw C pw

Thus, the out let temperature of heat transferring fluid is determined by

T E =∆ T + T i=111+25=135 ℃

5.6 Design summary

Table 5.17The thermodynamic analysis summary

Mass flow rate¿ Enrgy added energy T E of Cooling
load( kw )
¿ the demanded H2O(OC)

generator ( Kw ) ¿ PSTC ( Kw )

m ss mws NH 3 H2O 941 360 135 1350

0.572 0.181 0.39 0.78

Table5.18 The dimensional design out puts summary

Collector Wa 1.414m

L 3m

G/HANNES T. And KINDALEM T. Page cxviii

 DESIGN of SOLAR COOLING SYSTEM for AIR 2015
HANDLING UNITS of GARMENT ROOMS’ AC SYSTEM

HP 0.3535m
f 0.3535mm

Absorber tube Do 25mm

Di 22mm
La 3.3m

Thickness 3mm

Cover glass D Oglass 37mm

Diglass 34mm
Thickness 3mm

Lcover 3288mm

CHAPTER- SIX
Conclusion and recommendation

6.1Conclusion

Designing solar cooling (solar absorption cooling) is very important in case of current status
of our country because it is going to serve not only for MAGARMENT but also the
community, save money which would be used for importing from abroad and is also good
business for the designers and manufacturers. It is very important for saving unequal
distribution of electricity in either MAGARMENT TEXTILE factory or in remote area.

The design procedure we followed is based on many text and web references. There may be
so many modifications to this work because it designed without looking at previously done
related material.

G/HANNES T. And KINDALEM T. Page cxix

 DESIGN of SOLAR COOLING SYSTEM for AIR 2015
HANDLING UNITS of GARMENT ROOMS’ AC SYSTEM

This cooling system was designed with simplicity as a focus for manufacturing,
maintenance and daily use. Reducing the cost could increase its availability; reduce
maintainability, even making the technology available for air conditioning and to families
for food preservation. This was done as best as we can assume that the machine will be
manufactured from locally available materials and this work is going to be a good reference
for those who want to deal with related works. The cooling load that have been calculated
by using the “MAGARMENTROOMS’” data in chapter five is 1450kw in which it is put in
the summary of cooling load table. Thus, by using this load we have calculated the output
temperature of water which is used as heat exchanging medium in the parabolic trough
collector for fluid that are found in the generator.

6.2 Recommendation

 If it is set free ammonia is dangerous. Thus proper care should be given in handling
the ammonia and allow the illiterate to be in nearby.
 Steel pipes are easily affected susceptible to corrosion and deterioration due to
weather. Thus proper weather protection should be provided.
 For those who want to deal with solar refrigeration we recommend them focus on
solar adsorption refrigeration using ethanol because it is now produced in mass in
Ethiopia and it has good characteristics.
 For the vaccines not to be affected by weather like wind and sun, provide it with
housing.

G/HANNES T. And KINDALEM T. Page cxx

 DESIGN of SOLAR COOLING SYSTEM for AIR 2015
HANDLING UNITS of GARMENT ROOMS’ AC SYSTEM

Bibliography

1. Arora C.P., R. a Trott and T.C.Welch, Refrigeration and Air conditioning, 3rd edition,
McGraw-hill book, 2000 A.

2. A. Duffies and W.A.Beckman, solar engineering of thermal processes, John Wiley and
Sons, Madison, 1980

3. A closed parabolic trough collector,/retrieved 4-3-2012/ accessible at. (2015, 3 4)

http://www.wims.uncle.fr/xiao/solar/collector

4. Binay, heat transfer:principle and applications, University of Calcutta, 2001 Binay, heat
transfer:principle and applications, University of Calcutta, 2001

G/HANNES T. And KINDALEM T. Page cxxi

 DESIGN of SOLAR COOLING SYSTEM for AIR 2015
HANDLING UNITS of GARMENT ROOMS’ AC SYSTEM

5. Danison G., Refrigerant pumping hand book, depour de namours and company, Canada,
2001

6. .E.C.Guyer and D.L. Brownell, thermal design, Hamilton printing enterprise, Newyork,
1999

. 7. F.P.Incropera and D.P.Dewitt, Introduction to heat transfer, 3rd edition, John Wiley and
Sons, Canada, 1996 Haresh Khemani, Ammonia-Water Vapor Absorption Refrigeration
System, Published Mar 11, 2010

8. Haresh Khemani, Ammonia-Water Vapor Absorption Refrigeration System, Published

Mar 11, 2010

9. Hpgarg Jrakasl, solar energy,india first edition,2000

10.History of refrigeration,/retrieved 21-5-2012/ accessible

athttp://www.nptel.iitm.ac.in/..../iity.20%kharagpur

11. Hpgarg Jrakasl, solar energy,india first edition,2000

12. ISAAC solar ice maker,/retrieved 19-4-2012/ accessible at

http://www.concept.com/isaac

13. Joint international conference on sustainable energy and environment

14. J.B.Jones.R.e.Dugan,Engineering thermodynamics, technology division Institute,

Alexanderia, Virginia first revised edition, 2000

15. Kuppan T., Heat exchanger design hand book, Marcel Dekker, New York, 2000

16. Manohar Prasad, Refrigration and air conditioning,India, second edition,2003

17. Manual making of parabolic trough collector, /retrieved 4-3-2012/ accessible

athttp://www.wims.uncle.fr/xiao/solar/collector

18. Modeling and simulation of solar absorption cooling for India, accessible at

http://www.docstoc.com/.../modeling & simulation of solar absorption

19. Prasad M., Refrigeration and Air conditioning, 2nd edition, New agri international, 2003

G/HANNES T. And KINDALEM T. Page cxxii

 DESIGN of SOLAR COOLING SYSTEM for AIR 2015
HANDLING UNITS of GARMENT ROOMS’ AC SYSTEM

20. Profesor C.Parora, Refrigration and air conditioning India second edition, 2000
Danison G., Refrigerant pumping hand book, depour de namours and company, Canada,
2001

21. Professor Zakaison, Solar energy fundamentals and modeling techniques; Atmosphere,
Environment, Climate and Renewable energy, Istanbul Technical University, Istanbul, 2008

22. Professor Zakaison, Solar energy fundamentals and modeling techniques; Atmosphere,
Environment, Climate and Renewable energy, Istanbul Technical University, Istanbul, 2008

23. Ramesh k.shah and Dusan p. Sekulic,Fundamentals of heat exchanger design, John
wiley and sons, New jersey, 2003

24. .R.E.Sonntag, C.Borgnake and G.j.Van wylen, Fundamentals of Thermodynamics, John

wiley and sons inc., New delhi, 2003

25. S.P.Sukhatme, solar energy, principles of thermal collection and storage, second edition
, 1996

26. Sukhatme S.P, Solar energy, 2nd edition, McGraw hill, New Delhi, 1996

27. The design and development of solar powered refrigerator, /retrieved 4-6-2012
/accessible athttp://www. en.wikipedia.org /solar powered refrigerator

28. The effective length of solar parabolic concentrating collector Thermodynamic

simulation of solar absorption refrigerator ,/retrieved 11-5-2012/Accessibleat
http://www.iies.faces.ula.velamse2000/papers/simulation/msnn2000-Bula

29. Thermodynamic simulation of solar absorption refrigerator ,/retrieved 11-

52012/Accessibleathttp://www.iies.faces.ula.velamse2000/papers/simulation/msnn2000-
Bula

30. Whitman.Johnson.Tomczyk, Refrigeration and air conditioning fifth edition, 2005

G/HANNES T. And KINDALEM T. Page cxxiii

 DESIGN of SOLAR COOLING SYSTEM for AIR 2015
HANDLING UNITS of GARMENT ROOMS’ AC SYSTEM

Appendices

Appendix-A-1
List of Symbols Nomenclature

Aa Aperture area

 Aab Absorber area

 Ag area of the glass

 AST Apparent solar time

 C Condenser

 C' geometry concentration ratio

 Cp specific heat capacity of water

G/HANNES T. And KINDALEM T. Page cxxiv

 DESIGN of SOLAR COOLING SYSTEM for AIR 2015
HANDLING UNITS of GARMENT ROOMS’ AC SYSTEM

 Di Inside diameter of the receiver tube

 Do Outside diameter of receiver tube

 E Evaporator
 EV Expansion valve
 EXH heat exchanger

 F mass handled by solution pump

 f Focal length of the parabola

 f' quality of rich solution

 G Generator

 hf coefficient of convictive heat transfer fluid

 h Hour angle

 HP Height of parabola

 HO daily extraterrestrial radiation on horizontal surface

 hs Hour angle in sun set

 Ib Beam radiation

 Id Daily average diffuse radiation on horizontal surface

 Ig daily average solar radiation on horizontal surface

 It daily average solar radiation on tilted surface

 i day number

 I bt A beam radiation on tilted surface

 Lcover Length of cover glass

 L Length of parabola

 Lr Length of receiver

 L Latitude angle

 PS Solution pump

 ṁ Mass flow rate of refrigerant

 m NH 3 Mass flow rate of ammonia

 ṁ ss Mass flow rate of strong solution

 mw Mass flow rate of water

 ṁ wsMass flow rate of weak solution

 N Any day of the year

 n day length

 Qd Energy demand collected by the

collector

G/HANNES T. And KINDALEM T. Page cxxv

 DESIGN of SOLAR COOLING SYSTEM for AIR 2015
HANDLING UNITS of GARMENT ROOMS’ AC SYSTEM

 Qg Heat input into generator

 QL Amount of cooling load

 Qs The amount of solar radiation from the

sun
 Rb Ream radiation tilted factor

 Rr Rim radius

 rd diffuse radiation factor

 Rr reflective radiation factor

 Ta ambient temperature

 TE Outlet temperature of heat transferring fluid

 Ti expected inlet temperature

 TI Inside temp. of the roof

 T max maximum out door TO

 TO Outside temp. of the roof

 TR In door room temperature

 U Over all heat transfer coefficient

 Ug thermal transmittance of the glass

 Ul Overall heat loss coefficient for blackened steel

pipe
 Wa Width of aperture

 y Circulation ratio
 Z Solar azimuth angle

 Zs Azimuth surface angle

Appendix- A-2
List of Greek symbols Nomenclature

 δ Declination angle
 ξ ss Mass fraction of weak solution
 ξ ws Mass fraction of strong solution
 ηth Thermal efficiency
 ηo Optical efficiency
 λ Quality of weak solution
 φr Rim angle of the parabola
 α Solar altitude angle

G/HANNES T. And KINDALEM T. Page cxxvi

 DESIGN of SOLAR COOLING SYSTEM for AIR 2015
HANDLING UNITS of GARMENT ROOMS’ AC SYSTEM

 θz Zenith angle on horizontal surface

 γ Slope angle
 θt Zenith angle in tilted surface
 ρ air density

Appendix- B-1

Table:1 Three years average data solar hours

Month(M) Hour (sun shine hour)

January 10.22
February 10.3
March 8.1
April 9
May 10
June 6.6
July 5
August 4
September 7.2
October 9.55
November 11.1
December 9.4

Appendix-B-2

Table.2 Day number and recommended average day for each month

Month(M) Day number Average day of the month

Date ( i ) N

January i 16 16
February 31+i 15 46
March 59+i 16 75
April 90+i 15 105
May 120+i 16 136
June 151+i 15 166
July 181+i 17 197
August 212+i 16 128
September 243+i 15 258
October 273+i 15 289
November 304+ i 14 319
December 334+ i 10 350

G/HANNES T. And KINDALEM T. Page cxxvii

 DESIGN of SOLAR COOLING SYSTEM for AIR 2015
HANDLING UNITS of GARMENT ROOMS’ AC SYSTEM

Appendix-B-3
Thermodynamic Properties of Water
(source of saturated liquid –vapour of water, CPARRORA, Refrigeration and Air
conditioning.2nd edition, 5)

Table- A-6-1 water liquid-vapor saturation

T (℃) P ( kpa )
vf
m3
( )
kg
vg
m3
( )
kg
hf ( kJkg ) hfg ( kJkg ) hg ( kJkg )
10 1.2281 0.001 0.0106 41.99 2488.7 2509.7

15 1.7029 0.001001 0.7733 62.93 2465.1 2537.2

25 3.1656 0.001003 0.4314 140.76 2441.5 2546.3

30 4.2455 0.001004 0.329 125.67 2429.6 2555.3

35 5.6225 0.001006 0.2513 146.59 2417.8 2564.4

40 7.3717 0.001008 0.19528 167.5 2405.9 2573.4

45 9.5844 0.00101 0.1522 188.42 2393.9 2582.3

50 12.344 0.001012 0.12037 209.33 2381.9 2591.2

55 15.745 0.001015 0.09552 230.24 2309.8 2600

60 19.932 0.001017 0.07674 251.15 2282.4 2608.8

65 25.016 0.00102 0.06189 1345.4 2617.7

70 31.176 0.001023 0.05045 2333.1 2626.1

75 38.373 0.00126 0.04176 313.96 2320.7 2634.7

80 47.73 0.00129 0.034088 334.93 2308.2 2643.1

85 57.8 0.001297 0.02826 355.92 2295.5 2651.4

90 70.041 0.00104 0.023617 376.93 2282.27 2660.1

Appendix- B-4
Thermodynamic Properties of R-717(ammonia)

G/HANNES T. And KINDALEM T. Page cxxviii

 DESIGN of SOLAR COOLING SYSTEM for AIR 2015
HANDLING UNITS of GARMENT ROOMS’ AC SYSTEM

Source of saturated liquid vapour of ammonia (717), C.PARORA, Refrigeration, and Air
conditioning, second edition, 2000, 8)

Table A-8-1 717(ammonia) liquid- vapor saturation table

T (℃) P(kpa)
vf
m3
( )
kg
vg
m3
( )
kg
hf ( KgkJ ) h fg ( KgkJ ) hg ( KJKg )
-20 190.2 0.001504 0.6233 256.2 1344.6 1691.7

-15 236.3 0.001519 0.5084 278.8 1329 1797.9

-10 290.8 0.001534 0.4181 301.8 1312.9 1803.8

-5 354.9 0.00155 0.3465 324.4 1379.4 1909.3

0 429.5 0.001566 0.2892 347.5 1261.8 214.4

5 515.9 0.001583 0.243 370.70 1243.7 2220.8

10 615.2 0.006 0.2054 394.1 1225 2228.1

15 728.6 0.00619 0.1746 417.7 1205.8 2329.4

20 857.5 0.00138 0.1492 441.4 1185.8 2407.3

25 1003.1 0.00166 0.1281 465.4 1485.2 2445.6

30 1166.1 0.00168 0.1105 479.6 1143.9 2483.4

35 1350.3 0.001702 0.0757 483.9 1121.7 2450.53

40 1534.8 0.001725 0.0831 488.6 1098.8 2453.3

45 1781.9 0.00175 0.0725 495.4 1074.9 2458.03

50 2033 0.00177 0.0634 508.6 1050 2460.06

55 2309.9 0.001804 0.0556 514.1 1024.1 2464.6

60 2664.2 0.00183 0.0488 529.4 996.9 2467.8

65 2947.6 0.001866 0.043 535.1 995.5 2479.1

G/HANNES T. And KINDALEM T. Page cxxix

 DESIGN of SOLAR COOLING SYSTEM for AIR 2015
HANDLING UNITS of GARMENT ROOMS’ AC SYSTEM

Appendix- B-5
Degree of supper heated vapour of (R-717)
(Engineering thermodynamics J.B JONE. R.EDUGAN, first edition, 1996, 6)
Table A -8-2 Ammonia supper heat vapour
T ( ℃ ) P ( Kpa ) 50℃ 100℃
kJ ( KJ )
v
m3
( )
kg
h ( )
Kg
S
Kgk v
m3
( )
kg
h ( kJkg ) S( Kgk
kJ
)
-40 0.718 1.82 1517 6.665 2.08 3728 7.016

-35 0.932 1.45 1526 6.752 1.76 3734 6.916

-30 1.196 1.24 1535 6.483 1.45 3745 6.827
-25 1.516 0.96 1544 6.399 1.15 3754 6.741

-20 1.9 0.78 1553 6.319 0.9 3765 6.659

-15 2.36 0.61 1561 6.243 0.73 3794 6.581
-10 2.69 0.53 1570 6.171 0.59 3803 6.507
-5 3.55 0.42 1578 6.102 0.49 3813 6.437
0 4.29 0.36 1586 6.036 0.42 3902 6.37
5 5.16 0.3 1594 5.974 0.35 4011 6.247
10 6.15 0.5 1601 5.856 0.285 4021 6.189
15 7.28 0.22 1608 5.801 0.5 4030 6.159
20 8.57 0.185 1615 5.748 0.215 4039 6.147
25 10.01 0.65 1622 5.648 0.18 4048 6.129
30 11.67 0.137 1628 5.601 0.16 4054 6.11
35 13.5 0.118 1634 5.555 0.14 4069 6.056
40 15.54 0.11 1640 5.51 0.12 4170 5.935
45 17.84 0.09 1646 5.55 0.105 4278 5.89
50 20.33 0.07 1651 5.5.51 0.085 4503 5.847

Part and assemble drawing of solar collector

1. Part drawing
 Pipe

G/HANNES T. And KINDALEM T. Page cxxx

 DESIGN of SOLAR COOLING SYSTEM for AIR 2015
HANDLING UNITS of GARMENT ROOMS’ AC SYSTEM

 Receiver tube

 Glass cover ( Cover tube)

 Parabolic trough

G/HANNES T. And KINDALEM T. Page cxxxi

 DESIGN of SOLAR COOLING SYSTEM for AIR 2015
HANDLING UNITS of GARMENT ROOMS’ AC SYSTEM

2. Assembled drawing

G/HANNES T. And KINDALEM T. Page cxxxii

 DESIGN of SOLAR COOLING SYSTEM for AIR 2015
HANDLING UNITS of GARMENT ROOMS’ AC SYSTEM

G/HANNES T. And KINDALEM T. Page cxxxiii

 DESIGN of SOLAR COOLING SYSTEM for AIR 2015
HANDLING UNITS of GARMENT ROOMS’ AC SYSTEM

G/HANNES T. And KINDALEM T. Page cxxxiv