BDA 37501

Thermofluid Engineering Laboratory

FIRST EDITION

Mohamad Farid bin Sies

Ahmad Fuad bin Idris
Wan Saiful-Islam bin Wan Salim
Hanis bin Zakaria

FACULTY OF
MECHANICAL AND MANUFACTURING
ENGINEERING

Cetakan Kedua (Modul Pembelajaran), 2023

© Mohamad Farid bin Sies, Ahmad Fuad bin Idris, Hanis bin Zakaria

SEMESTER II 2022-2023

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Hak cipta terpelihara. Tidak dibenarkan mengeluar ulang mana-mana bahagian artikel, ilustrasi dan isi
kandungan buku ini dalam apa-apa bentuk dan cara apa jua sama ada secara elektronik, fotokopi,
mekanik atau cara lain sebelum mendapat izin bertulis dari penulis.

Edisi ini merupakan edisi Modul Pembelajaran yang diterbitkan tanpa melalui proses penilaian dan
penyuntingan. Mutu edisi ini akan diperbaiki dari semasa ke semasa berdasarkan maklum balas yang
diterima daripada aktiviti pengajaran. Sebarang pelanggaran atau unsur yang bertentangan dengan
aspek etika penulisan dan hak cipta adalah di bawah tanggung jawab penulis. Edaran modul hanya
dibenarkan di dalam kawasan atau premis Universiti Tun Hussein Onn Malaysia (UTHM) atau mana-
mana cawangannya sahaja. Pengedaran di luar UTHM memerlukan kebenaran bertulis dari penulis dan
penerbit UTHM.

Diterbit dan dicetak oleh:

Penerbit UTHM
Universiti Tun Hussein Onn Malaysia
86400 Parit Raja, Batu Pahat
Johor Darul Ta’zim.
Tel: 07-453 7454
Faks: 07-4536145
E-mel: pt@uthm.edu.my
Laman Web: www.uthm.edu.my/pt

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CONTENTS PAGE

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 INTRODUCTION

This module of Thermofluid Engineering Laboratory (BDA 37501) is published

to standardize the teaching materials for all sections in the Faculty of
Mechanical and Manufacturing Engineering, Universiti Tun Hussein Onn
Malaysia.

AIM

The part aims to provide students with the knowledge to relate the principal of

theory studied in Fluid Mechanics and Thermodynamics with the applied field.

Thermofluid Engineering Laboratory (BDA 37501) module combines Fluid

Mechanics Laboratory and Thermodynamics Laboratory. In this module,

laboratory procedures and figures will help the students practice good

laboratory conduct, produce good laboratory reports, and provide a better

understanding of Fluid Mechanics and Thermodynamics. According to

professional practice, this module also helps students get information, explore

theoretical applications, and complete tasks.

OBJECTIVES

The objectives of this laboratory module are to educate students to:

1. Perform practical work according to the procedure, instruction, and

specified aims while using equipment efficiently to obtain data and
information and solve problems scientifically.
2. Prove theory based on experiment, observation, data processing, and
information.

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3. Encourage healthy attitudes such as truthfulness, dedication, discipline,
cooperation, creativity, and safety awareness.
4. Develop high skills in producing quality work, preparation, and
professional report presentation.
COURSE LEARNING OUTCOMES

At the end of this course, the students will be able to:

1. Communication – Perform effectively complex engineering experiments

applying the general ideas of the subject through an oral presentation
and written reports. (LOD 8, P5, LO3)
2. Investigation - Conduct investigation through experiments that display
basic skills and knowledge of Fluids Mechanics and Thermodynamics
using various laboratory equipment. (LOD 4, C4, LO4)
3. Investigation – Analyze original data from experiments and compare
them with fundamental theory. (LOD 4, C3, LO4)
4. Individual and Team Work - Work effectively in a group as a member
and leader through laboratory experiments and presentations. (LOD 11,
A3, LO5)
SYNOPSIS

This module covers several experiments for Fluid Mechanics and

Thermodynamics.

Fluid Mechanics II experiments cover:

Open Ended Fluid laboratory project instruction

Thermodynamics II experiments covers:

1. Marcet Boiler, Clausius-Clapeyron Equation

2. Boyle’s Law
3. Two-Stage Air Compressor
4. Air Conditioning System
5. Cooling Tower
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 ASSESSMENT
MARKING SCHEME

Overall marks for practical comprises of:

i. Fluid Mechanics Laboratory 50 %

ii. Thermodynamics Laboratory 50 %

Total: 100 %

MARKING SCHEME FOR FLUID MECHANICS LABORATORY

i. Investigation (PLO4) 60 %
ii. Communication (PLO3) 40 %
iii. Teamwork assessment (PLO5) 40 %

Total: 100 %

* Total marks consist of 50 % overall final marks

MARKING SCHEME FOR THERMODYNAMICS LABORATORY

i. Report (average of number of reports) 70 %
ii. Oral test 25 %
iii. Group member assessment 5 %

Total: 100 %

* Total marks consist of 50 % overall final marks

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 REPORT PREPARATION GUIDELINE

An experimental practical report aims to enable the students to show all

relevant results, measurements, and observations obtained during the
experiment. Therefore, students must be alert, ready, and responsive to the
task. Any results or observations must be recorded and presented in tables or
graphs. The findings are to be discussed thoroughly. At the end of the report,
a summary must be presented.

The report has to be completed in the allocated time and has to cover the
following aspects:

Full practical report assessments for the Fluid Mechanics laboratory are:

1. Title
2. Objectives 5%
3. Learning outcomes 10 %
4. Theory 15 %
5. List of Equipment 15 %
6. Experiment Procedure 10%
7. Result 15%
8. Discussions 15 %
9. Conclusion 10 %
10. References 5%

Total: 100 %

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Practical report assessments for the Thermodynamics laboratory
are:

1. Results 15 %
2. Observations 25 %
3. Calculation 15 %
4. Discussions 30 %
5. Conclusion 15 %

Total: 100 %

PRESENTATION PROCEDURE (FLUID MECHANICS II AND

THERMODYNAMICS II LABORATORY)

Each student is to attend a group oral test session as an assessment for

understanding the experiment and the findings. The presentation session will
be conducted in a group, but the marks will be based on individual
performance.

Presentation Assessment (individual) 25 %

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 PEER ASSESSMENT (FLUID MECHANICS II AND
THERMODYNAMICS II LABORATORY)

Each student is also responsible for assessing other group members'

performance. An assessment form will be given to the students, and the
assessment has to be based on truthful observation throughout the practical
class. Peer assessment by group members includes the following criteria:
cooperation, communication, responsibility, commitment, ability to work within
the time frame, and quality of work.

Group Member Assessment (individual) 5%

** PLEASE BRING NECESSARY REFERENCE BOOKS DURING THE

PRACTICAL SESSIONS

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 LABORATORY GENERAL RULES
1. Students must perform all practical activities as determined in the
schedule. Any changes will be notified by the designated
lecturer/instructor/tutor.
2. Practical attendance is compulsory and should not be less than 80%.
Students have to record their attendance. Non-attendance must be verified
by supporting documents.
3. A practical report has to be submitted within one (1) day after the class to
the designated lecturer/instructor/tutor on duty. A LATE REPORT WILL
LEAD TO EITHER ZERO OR REDUCED MARKS.
4. Students have to be appropriately dressed according to university
regulations. Additional safety and health regulations must adhere to
accordingly.
5. Students who are late without reason can be barred from performing an
experiment on that day and assumed not present. This also applies to
students that leave the class without permission from the designated
lecturer/instructor/tutor.
6. Students are not allowed to smoke, eat or drink during practical classes.

RULES AND REGULATIONS DURING EXPERIMENT

1. Students must ensure that they thoroughly understand the experiment in
terms of aim, procedures, data acquisition method, and expected results.
2. Before attending the practical class, students should read and understand
the experimental procedures. Additional readings and references to
enhance the understanding in performing experiment are strongly advised.
3. Students are required to bring their own stationeries involved in the
experiments, such as pencil, pen, A4 paper, graph paper, and etc.
4. Every experiment has to be completed in the allocated time.
5. Experimental apparatus should not be moved to other location, unless
requested to do so.

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6. Before leaving the laboratory, students are to:
a. Clean the table and workplace.
b. Return the experimental apparatus to its original location.
c. Ensure that the designated lecturer/instructor/tutor on duty verify the
practical report submission.

REFERENCES

All references were combined and attached at the end of each topic.

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 TOPIC 1

OPEN-ENDED LABORATORY PROJECT INSTRUCTION

INTRODUCTION

An open-ended experiment employs outcome-based education. It is a student-

centered learning philosophy that focuses on empirically measuring student
performance, which is called outcomes. Thus, in this open-ended laboratory
project, a problem will be given to a group of student to solve or complete by
conducting certain experimental work within a specified time. Student should
actively participate in discussion either in or out lab class.

TASK

Students are required to design an apparatus related to flow properties or fluid

properties. Students will be divided into small group and each group consists
of 4 to 5 students. Each group is required to do the following task:

i. Design and fabricate an apparatus that can measure flow

properties or fluid properties.
ii. Construct a lab/experiment instruction for that apparatus. The
lab/experiment instructions should consists of :
a. Title
b. Objective
c. Learning outcomes
d. Theory
e. List of Equipment
f. Experiment Procedure
g. Result
h. Discussion
i. Conclusion
j. References
iii. Provide a full report for that apparatus including sample of data.
iv. For the purpose of presentation, each group is required to
provide A3 laminating poster.

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EVALUATION CRITERIA

Evaluation criteria are as follows:

i. Proposal 20% (Group) - Investigation

ii. Lab/Experiment Instruction 20% (Group) - Investigation
iii. Weekly Progress 20% (Individual and Group) -Team Working
iv. Full Report 20% (Group) - Investigation
v. Presentation 20% (Individual and Group) -
Communication

PROJECTS MILESTONES

This project will be conducted in 6 weeks with full supervision of Lab

Instructor and Lab Technician. Students are expected to design a new
experiment but all technical expects of equipment, tools, and lab resources
must be consulted by the Lab Technician.

WEEK ACTIVITY
1 Students will be divided into small group and each group consists
of 4-5 students. Each group is required to propose their open
ended laboratory project based on title/scope given by the
instructor
2 All groups are expected to come up with their detail apparatus
design
3 Fabricate an apparatus
4 Do an experiment and construct lab/experiment instruction.
5 Produce experiment full report
6 Project presentation

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REFERENCES

1. Yunus A. Cengel and John M. Cimbala, Fluid Mechanics Fundamentals

and Applications, 3rd Edition, McGraw Hill, 2014.
2. Bruce R. Munson et. al., Fundamentals of Fluid Mechanics, 10 th
Edition, Wiley, 2013.
3. Frank M. White, Fluid Mechanics, 7th Edition, McGraw Hill, 2011.
4. Merle C. Porter, Mechanics of Fluid, 4th Edition, Cangage Learning,
2012.
5. John F. Douglas, Fluid Mechanics, 6th Edition, Prantice Hall, 2011
6. Robert W. Fox, Fluid Mechanics, 8th Edition, John Wiley, 2012.

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 TOPIC 2

BOILER EFFICIENCY

TOPIC LEARNING OUTCOMES

At the end of this topic, students will be able
a. Calculate the boiler efficiency
b. Determine the boiler equivalent evaporation
c. Calculate the thermal efficiency based on BS845

CONTENT
2.1 INTRODUCTION
This experiment exposes students to how to evaluate the boiler's performance.

2.2 EXPERIMENTAL THEORY

2.2.1 EVAPORATION
The evaporation of a boiler is stated in kg per hour, known as the boiler’s
capacity.

2.2.2 BOILER PERFORMANCE

It may be regarded as the steam produced per unit of fuel, or the efficiency
may be used as a performance measure. The comparison of two boilers can
only be made based on the weight of the steam produced per hour when both
use the same fuel, have the same feed-water temperature, with the same
working pressure. Actual feed temperatures and working pressure vary widely,
and a standard feed temperature and operating pressure are necessary. The
feed temperature adopted is 100oC, with the atmospheric pressure. This
condition requires only the latent heat of 1 kg of steam at the atmospheric to
evaporate 1 kg of water. This latent heat is 2257 kJ/kg, and since this heat
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produces 1 kg of steam under standard conditions, it is called the Standard
Evaporation Unit.

2.2.3 BOILER EFFICIENCY

energy gained by fluid
Boiler efficiency can be defined as
total energy input
Energy gained by fluid
= m s x (hs − h f w )

= m s x (h f + h f g ) − h f w 

= m s x (h f + xh f g ) − (Cp x (t f w ))
where
ms = steam mass flow rate
hs = specific enthalpy for steam
hfw = Specific enthalpy for feed water
hfg = specific enthalpy for vaporisation (latent heat)
hf= specific enthalpy for saturated liquid (sensible heat)
x = dryness fraction of steam

Cp = Specific heat at a constant pressure of feed water

tfw = temperature of feed water

Note that the enthalpy figures above are for absolute pressures, and the
gauge reading plus the atmospheric pressure gives the absolute pressure of
steam. To convert the barometric reading of the atmospheric pressure bar:
B x 13,600 x 9.81
Pat =
10 5
Pat = 1.334 x B bar
Where:

Pat = Atmospheric pressure

B = barometric reading in meters
13,600 is the density of mercury in kg/m3
9.81 is the acceleration due to gravity in m/s2
105 newton/m2 is 1 bar.

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Total energy input is given by fuel rate multiplied by the calorific value of the
fuel.

i.e., Total energy input = (m f x density of fuel ) x Cv f

Where:
mf = fuel mass flow rate

Cv f = Gross calorific value of fuel

2.2.4 CALORIFIC VALUE OF THE FUEL

The calorific value of a fuel may be obtained approximately from a chemical
analysis of a sample. The constituents are usually carbon, hydrogen, sulphur,
nitrogen, oxygen, and residual ash. Only carbon, hydrogen, and sulphur
contribute to the calorific value of these elements.

Hydrocarbon fuels produce carbon dioxide and water vapour when burned.
Water vapour retains a certain quantity of “latent” heat (about 1.88 MJ/m 3),
irrespective of its temperature, which is not released unless it is cooled
sufficiently to change its state from vapour to liquid water. Therefore, these
fuels have two calorific values: higher or gross. It includes this latent heat and
the lower or net value. On the basis that this latent heat is not available as
useful heat in conventional boilers because water vapour is not condensed but
is discharged in the flue still as vapour.

Suppose hydrogen in a fuel can be burnt entirely to form water. The Higher
Calorific Value for the fuel is 143 MJ/kg. If the water vapour initially formed is
not allowed to condense, the heat liberated will only be 120.5 MJ/kg (this gives
the Lower Calorific Value of fuel). Typically for natural gas, the Higher Calorific
Value is 38.2 MJ/m3, and the Lower Calorific Value is 34.4 MJ/m3(both values
at Metric Standard Conditions). The Calorific Value obtained from a “bomb”
calorimeter experiment is the ‘Higher’ one, and this is the figure used to
calculate boiler performance and efficiency.

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Fuel Data: from gas supplier published data, the calorific value of the gas fuel
at MSC is obtained, i.e., natural gas 38.2 MJ/m3, propane 93 MJ/m3, LPG
97.86 MJ/m3. Note that the volume of gas flowing should be corrected to MSC
conditions.

Note: The fuel composition is obtained from standard data if oil firing is used.
The Calorific Value of type D Fuel Oil is generally taken as 45.59 MJ/kg and
850 kg/m3 density.

2.2.5 CORRECTION OF GAS RATE

The gas rate measured by a meter under the prevailing conditions can be
corrected to MSC (Metric Standard Condition of 15oC and a total pressure of
1013.25 mbar) by application of the following correction factor:

(B + p ) x 288 
Correction factor =  
1013.25  273 + T 

Where;

B = barometric pressure in mbar

p = gas pressure at meter in mbar
T = temperature of gas at meter in oC.

The measured rate should be multiplied by this correction factor to obtain the
MSC condition, or conversely. The required rate at MSC conditions should be
divided by the factor to adjust the burner rate under the prevailing conditions.

2.2.6 EQUIVALENT EVAPORATION

The evaporative capacity of a boiler is usually quoted as the rate in kg/hour at
which the steam is generated. The amount of steam generated depends on
the enthalpy change from feed water to the steam condition for a given firing
condition. Since the enthalpy of the feed water depends on its temperature.
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While the steam depends on the steam pressure and temperature, a simple
statement of capacity in kg/hour is insufficient unless the conditions are also
quoted. Operating conditions can determine boiler evaporation performance.
It is assumed that the feed water temperature is 100 oC and the dry saturated
steam is generated at atmospheric pressure. The equivalent evaporation F &
A (FROM and AT) 100oC may be determined from typical boiler operating
conditions as follows:

m s x (hs − h fw )
Equivalent Evaporation F & A 100oC =
h
Where:
ms = mass of steam generated
hs = enthalpy of steam at operating conditions
hfw = enthalpy of feed water at operating conditions
h = enthalpy of evaporation at 100oC and 1 bat. abs

Thus to generate 1 kg of steam, it is only necessary to supply the specific

enthalpy of evaporation, and this is obtained from steam tables.

i.e. h at 100oC = 2257 kJ.kg

Hence,
ms x (hs − (cp x (t fw )))
Equivalent evaporation of the boiler =
2257
where

ms = steam mass flow rate

hs = specific enthalpy for steam
cp = Specific heat at a constant pressure of feed water
tfw = temperature of feed water

2.2.7 THERMAL PERFORMANCE OF A BOILER

This section describes a concise procedure for conducting a thermal
performance assessment on a steam boiler using the indirect (losses)
approach as detailed in BS 845: Part 1. The test result can be based on the
fuel's gross or net calorific value.
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It provides a convenient means for assessing thermodynamically simple
boilers, i.e., having a single major source of heat input and a simple circuit for
water steam that does not condense moisture out of the flue gases.

The enthalpy value can be taken from steam tables or charts based on
standard procedures and linear interpolation. Four sources of losses To
determine boiler efficiency:

a. The loss due to sensible energy in the exit gases [L1]

b. The loss due to latent heat energy in the exit gases [L 2]
c. The loss due to incomplete combustion (not used here)
d. The loss from external surfaces of the boiler (assumed negligible)

We can ignore losses from incomplete combustion and surface losses for this
experiment since they are significantly less than sensible heat and latent heat.
It will give a slightly higher reading for the boiler efficiency, but the result will
be sufficiently accurate for an approximation.

The efficiency has been based upon the GROSS calorific value of the fuel.
The heat supplied by liquid fuels is given as:

Mass of fuel burned (kg )

Qigr = x Gross calorofic value of fuel kJ/kg
Duration of test(hour )

where Qigr = Rate of heat supply by fuel based upon the gross calorific
value

The heat supplied by gaseous fuels is given as:

Qigv = 1000 x flow rate of gaseous fuel corrected to MSC x gross calorific
value of the fuel.

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 The loss due to sensible heat in the dry flue gas, L1 is given as:

k gr x (Flue gas temperature - fuel temperature)

L1 gr =
VCO 2
where
k gr = Sierget constant

For class D fuel = 0.48

For LPG Butane = 0.43
For LPG Propane = 0.42
For Natural gas = 0.35

and

VCO 2 = Average CO2 concentration expressed in a

percentage.
For class D fuel = 11.6 % (approx)

The losses due to enthalpy in the water vapour in flue gases, L2 is given as:

(m )
+ 9 H x (2488 - 4.2t a + t fg )
L2 gr =
H 2O

Cv f

where
Cv f = Gross calorific value of fuel

m H 2O = Moisture content of fuel as burned %

H = Hydrogen content of fuel as fired
ta = Temperature of combustion air oC
tfg = Temperature of gases leaving boiler oC

H=
For class D fuel = 13%
For LPG Butane = 17.2 %
For LPG Propane = 18.2%
For Natural gas = 24.4%

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Fuel density =

For class D fuel = 850 kg/m3

For LPG Butane = 2.383 kg/m3
For LPG Propane = 1.869 kg/m3
For Natural gas = 0.732 kg/m3

All gases at MSC

% water content = by volume by mass

For class D fuel = 0.01% = 0.085%

For LPG Butane = 0.0% = 0.0%
For LPG Propane = 0.0% = 0.0%
For Natural gas = 0.0% = 0.0%

The thermal efficiency, Egr of the boiler is given by:

E gr = 100 − Ltgr
Where:
Ltgr = (L1 + L2 )gr
Where:
Ltgr = Total loss based on gross calorific value

L1 = Loss due to sensible heat in exit gases (%)

L2 = Loss due to latent heat in exit gases (%)

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2.3 EXPERIMENTAL EQUIPMENT
The “series 90” Bradlee steam boiler comprises the three-pass, flame reversal
fully wet back design constructed following BS2790 (Figure 3.1).

Figure 2.1 BRADLEE series 90 shell boiler

The shell consists of two fabricated steel cylinders arranged eccentrically with
each other. The inner cylinder is closed at the rear by a flat plate connected to
the rear tube plate by several stay bars, thus forming a wet back and plain
surface. The rear tube plate is welded to the rear of the outer cylindrical shell
and is connected to the front tube plate by the convection tubes consisting of
plain and stay tubes. Stay bars are used for tube plate bracing above the tube
banks. The convection tubes are welded to the front tube plate and the open
end of the plain furnace. The front of the outer cylinder is also welded to the
front tube plate.

On the top of the shell are connections for the pressure gauge, pressure
switches, inspectors test cock, water level controls, steam stop valve, and
steam safety valve. A manhole of the boiler is provided on the top centre line
of the shell.

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The boiler door is mounted on the front of the shell through heavy-duty hinges
and closed by the door flange bolting to the shell-mating flange. The door is
internally insulated to withstand the heat of the combustion gasses and to
reduce heat loss through the door. A gasket is provided between the door
flange and the shell flange to give the effect of a gas-tight seal. The door is
machined to accept the burner draught tube and a flame observation port. The
door is supplied with a door-closed micro switch to prohibit burner firing when
in the open position.

The boiler smoke box is located at the rear of the boiler shell and is supplied
with a bolted closing plate. The closing plate has lift handles or lugs and a
removable access panel designed to gain entry for cleaning and access to the
rear shell mud hole. The circular flue spigot is located on the top centreline of
the smoke box and is supplied with a plugged socket for test instruments. The
smoke box is provided with a plugged drain connection.

The boiler has a fully automatic monobloc type duel firing burner for ON/OFF,
HIGH/LOW, and modulation control.

The boiler is supplied with a dust and waterproof control panel to IEC 144 IP65
and is located at the front of the boiler. An internal chassis plate is fitted with
all relays, timers, starters, control equipment, fuses with MCB’s, terminal
blocks, and interconnecting wiring. Alarm bells are mounted on the side of the
control panel for burner lockout and water level fault conditions. A hinged front
access door is supplied with a panel facia into which various lights and
switches are fitted.

The boiler is supplied with a vertical multi-stage centrifugal feed water pump
mounted upon a mild steel stand attached to the boiler base frame, and the
boiler shell is covered with slab insulation and then encased in plastic-coated
mild steel sheeting.

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2.4 EXPERIMENTAL PROCEDURE
a. Set the boiler to raise steam at the required condition and allow
the condition to stabilize.
b. Note the time and run the boiler on loads, taking a reading of the
quantities of fuel and feed water used during the test.
c. Measure the dryness fraction using the Separating and Throttling
Calorimeter. The flue gas should be measured using a
Combustion Analyser.
d. Take a reading of the quantities listed on the data sheet. Measure
the temperature and pressure of the boiler gas fuel supply when
it fires the boiler. Steam pressure, feed water temperature, and
relevant flow rates shall be held as steady as possible and close
to normal operating conditions.
e. Following the establishment of the steady state, the test shall be
of sufficient duration for at least six (6) complete sets of readings
of fuel input or heat output rate, flue gas temperature, and flue
gas analysis to be carried out at 10 minutes intervals.

ACTIVITY 1

EXPERIMENTAL DATA
Refer to the data sheets provided in Appendix A and B.

RESULTS AND DISCUSSION

a. Complete all data required in the data sheets.
b. Calculate the required parameter.
c. Obtain the value of the boiler efficiency base on calculation and
standard BS845.
d. Give comments on the values obtained during calculation.

QUESTIONS
a. Describe two types of boilers used in engineering applications.
b. Describe the overall processes of the boiler in producing energy.

CONCLUSION
Deduce conclusions from the experiment. Please comment on your
experimental work in terms of achievement and problems faced throughout
the experiment and suggest recommendations for improvement.

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REFERENCES

1. Cengel,Y.A. and Boles,M.A. (2011).Thermodynamics: An Engineering

Approach., 7th Edition.New York : McGraw-Hill.
2. Sonntag,R.E. and Borgnakke C.(2007). Introduction to Engineering
Thermodynamics. 2nd edition. Hoboken, NJ : John Wiley.
3. Moran M.J and Shapiro H.N. (2010). Fundamentals of Engineering
Thermodynamics. 6th Edition. Hoboken, NJ : John Wiley.

26
 APPENDIX A

BOILER EFFICIENCY

DATA SHEET
OPERATING PRESSURE Average

Steam Pressure bar.g

Fuel Oil Pressure bar.g
Time sec
Barometric Pressure mmHg
Ambient Temperature °C
Feed Water Temperature °C
Fuel Oil Temperature °C
Steam Temperature °C
Flue Temperature °C
Flue CO2 %
Flue O2 %
Flue CO ppm
Steam mass flow rate from orifice
measurement kg/hr

Dryness fraction of steam -

Initial feed water meter reading ltr

Final feed water meter reading ltr

Initial oil meter reading ltr

Final oil meter reading ltr

Quantity of feed water m3

Quantity of fuel oil consume ltr

Calorific value of fuel oil MJ/kg

27
 APPENDIX B
BOILER EFFICIENCY

DATA SHEET

Observed reading

Steam Pressure bar.g

Fuel oil Pressure bar.g
Time Sec.
Barometric Pressure bar.g
Ambient Temperature Celcius
Feed water Temperature Celcius
Fuel oil Temperature Celcius
Steam Temperature Celcius
Flue Temperature Celcius
Flue CO2 %
Flue O2 %
Flue CO ppm
Fuel oil ltr
Feed water total volume ltr
Caloric value of fuel oil MJ/kg
Dryness fraction of steam
Steam mass flow rate from orifice measurement Kg/hour

Derived result

Steam Pressure bar.abs

Saturated liquid enthalpy kJ/kg
Latent heat kJ/kg
Enthalpy of wet steam kJ/kg
Energy to produce steam kJ/hour
Enthalpy of feed water kJ/kg
Boiler Equivalent F&A 100oC kJ/hour
Fuel oil used kJ/hour
Energy supplied in fuel oil kJ/hour
Boiler efficiency %

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 TOPIC 3
BOYLE’S LAW

TOPIC LEARNING OUTCOMES

At the end of this topic, students will be able to determine the relationship
between pressure and volume at a given constant temperature.

CONTENT

3.1 INTRODUCTION
Gases behave differently from the other two commonly studied states of
matter, solids and liquids, so we have different methods for treating and
understanding how gases behave under certain conditions. Unlike solids and
liquids, gases have neither a fixed volume nor shape. Instead, they are molded
entirely by the container in which they are held. The gas laws are physical laws
describing the behavior of a gas under various conditions of pressure, volume,
and temperature. One of the earlier gas laws was Boyle’s law (advanced by
Robert Boyle in 1662). He investigated the relationship between the volume of
an ideal dry gas and its pressure.

Four variables can be altered in a gas sample: pressure, volume, temperature,

and mass. All other variables must be held constant or fixed to investigate how
one variable will affect another. Boyle fixed the mass of gas and its
temperature during his investigation. He found that the pressure and volume
of a gas are inversely proportional to one another, or pV = k, where p is
pressure, V is volume, and k is a constant of proportionality. A practical math
expression of Boyle’s finding is as follows
𝑝1 𝑉1 = 𝑝2 𝑉2 = 𝐶 (3.1)
where, 1 = initial value
2 = final values
C = constant

29
3.2 EXPERIMENTAL THEORY

Boyle’s law is confirmed in this experiment using a gas chamber apparatus.

The gas chamber consists of a glass capillary open at one end. A certain
quantity of air is enclosed through mercury seals. At an outside pressure, po,
the enclosed air has a volume, Vo. Pumping off the air at room temperature
with a hand pump with under pressure ∆p for the outside pressure is generated
at the open end of the capillary. The mercury seal itself exerts pressure on the
enclosed air.
𝑝𝐻𝑔 = 𝜌𝐻𝑔 . 𝑔. ℎ𝐻𝑔 (3.2)

where, ρHg = density of mercury = 13600 kg/m3

g = acceleration of gravity = 9.82 m/s2
hHg = height of the mercury seal (m)

Therefore, the pressure of the enclosed air is,

𝑝 = 𝑝0 + 𝑝𝐻𝑔 + ∆𝑝 (𝑏𝑎𝑟) (3.3)

where, p0 = atmosphere pressure

pHg = pressure of mercury
∆p = pressure differential

The volume, V of an enclosed air column is determined by the pressure, p. V

can be calculated from the height, h of the air column and the cross-section of
the capillary, where,
𝜋𝑑 2 (3.4)
𝑉 = 𝐴. ℎ = . ℎ (𝑚3)
4

and d = inner diameter of the capillary = 2.7 mm

30
3.3 EXPERIMENTAL EQUIPMENT

The gas chamber, hand vacuum, pressure gauge stand base, stand rod, and
two clamp units with jaw clamp as shown in
Figure 3.1.

Gas chamber

Pressure gauge

Mercury seal

Hand vacuum hHg

pump

h (height of air column)

Ventilation valve

Figure 3.1: Boyle’s Law Apparatus

3.4 EXPERIMENTAL PROCEDURE

i. Mount the gas chamber in the stand device.
ii. Ensure the reading of the hand pump is 0 mbar, or push the
ventilation valve of the hand pump to reduce the pressure
differential, ∆p to 0.
iii. Measure and record the ambient temperature, To and the
atmosphere pressure, po.
iv. Measure the height of the mercury seal, hHg, from the scale of the
gas chamber.
31
 v. Read and record the height of the air column, h at ∆p = 0 (before
applying the pressure differential).
vi. Generate the pressure differential, ∆p = -50 mbar, read the height
of the air column, h, and record it together with ∆p.
vii. Repeat step (f) and record the data for every increment of -50
mbar until it reaches the maximum value of h.
viii. Measure the reading of ambient temperature, To, and
atmospheric pressure, po again.
(Note: Do not increase or decrease the pressure differential, ∆p too
quickly. It can cause the mercury to overshoot and cause a spill)

ACTIVITY 1

RESULT (15%)
a. Complete the data sheet provided in Appendix: Pressure and
Volume measurements.
b. Plot the pressure, p (bar) against volume, V (m3).
c. Plot the parameter 1/p (bar) against volume, V (m3).
d. Discuss your observations by giving comments on both of the
graphs plotted. Is Boyle’s Law true for this experiment? If it is,
determine the value of constant C.
e. Discuss the possible errors and the factors that can affect the
result of this experiment.

OBSERVATION (25%)
Please observe the experiment that you have conducted.

CALCULATION (15%)
Show your calculation.

32
DISCUSSION (30%)
a. Why does the ambient temperature need to be measured before and
after the experiment?
b. Will the deviations from the ’ideal’ behavior of Boyle’s Law be smallest
at larger or smaller volumes for a given fixed quantity of gas? Give the
justification for your answer.

CONCLUSION (15%)
Deduce conclusions from the experiment. Please comment on your
experimental work in terms of achievement. Describe problems faced
throughout the experiment and suggest recommendations for improvements.

REFERENCES
a. Yunus A. C. and Michael A. B. (2008). Thermodynamics: An
Engineering Approach (6th ed). USA: Mc Graw Hill. TJ265 .C46 2011
b. John P.O’ Connel and Haik J.M. (2005). Thermodynamics:
fundamentals for application. US: Cambridge University Press.
Cambridge. QC311 .O26 2005
c. Mott R.L. (2000). Applied Fluid Mechanics (5th ed). International Edition.
Prentice Hall. TA357 .M67 2006.

33
 APPENDIX A

BOYLE’S LAW
- PRESSURE AND VOLUME MEASUREMENT -

DATASHEET:
Atmospheric pressure, po (bar) = _______ (before experiment)
_______ (after experiment)

Ambient temperature, To (oC) = _______ (before experiment)

_______ (after experiment)

Height of mercury seal, hHg = _______ (mm)

∆p (mbar) h (mm) p (bar) 1/p (bar) V (m3)

34
 TOPIC 4
TWO-STAGE AIR COMPRESSOR

TOPIC LEARNING OUTCOMES

At the end of this topic, the students will be able to:

a. Understand the polytropic process in the two-stage air compressor.
b. Determine the polytropic efficiency of a compressor.

CONTENT

4.1 INTRODUCTION

An air compressor uses an electric motor to convert the electrical energy into
mechanical energy converted to thermodynamic energy in the form of
compressed air. It is utilized to raise the pressure of a volume of air, and
designs use at least the basic principles: Staging, Intercooling, Compressor
displacement, and volumetric efficiency. Compressors are staged to reduce
the temperature rise and improve compression efficiency. The temperature of
the air leaving each stage is cooled before entering the next phase
(Intercooling).
An after-cooling should also be used to reduce the air temperature before it
enters the receiver (storage tank) and to discharge the cooling medium to the
surrounding at a low temperature (see Figure 6.1).

1 After-cooler
4
Compressor
Compressor
second stage
first stage Storage

2
3

Intercooler

Figure 6.1: Two-stage Air Compressor Schematically

35
4.2 EXPERIMENTAL THEORY

4.2.1 COMPRESSOR OUTLINE

Referring to Figure 6.2 in Appendix A, the filtered free air is induced at the
first stage compressor intake (P0, T0) for the first compression. Before going
into the second stage compressor, this air is cooled by the heat exchanger to
reduce the high temperature after the first compression P1, T1). The air intake
condition for the second compressor is at P1 and T2. Before this final
compressed air is delivered into the storage tank, it is again cooled by the dual
heat exchanger (aftercooler) to reduce its temperature. The cooling medium's
temperature also decreases after the cooling process (T9). Water is used as a
cooling medium for both the heat exchangers. The mass flow rate shall be
regulated simultaneously during the operation to prevent unnecessary losses.

4.2.2 EQUATIONS

Air compression is a polytropic process in form pv

n
= const , where n is the
polytropic coefficient. With the assumption that the actual air is considered an
ideal gas with its characteristic equation pV / T = const , then we can obtain a
good relationship between the temperatures and pressure, or temperatures
and volume for any point during the process as follows:
𝑝𝑉 𝑛 = 𝐶 (4.5)

So, 𝑝1 𝑉 1 = 𝑝2 𝑉 2
And the property of the ideal gas follows the equation:

𝑝𝑉 (4.6)
=𝐶
𝑇
𝑝1 𝑉1 𝑝2 𝑉2
=
𝑇1 𝑇2

36
 From (6.2), it yields:
𝑇2 𝑝2 𝑉2 (4.7)
=
𝑇1 𝑝1 𝑇1

And together with equation (6.1), we obtain:

𝑛−1 (4.8)
𝑇2 𝑝2 𝑛
= ( )
𝑇1 𝑝1

(Note: index 1 and 2 refer to the air condition at the inlet and outlet of the
compressor, respectively).
The value for the thermodynamic properties p and T at the intake and the outlet
are measured.

4.2.3 Polytropic compression

a. Work and efficiency

The work required to compress the air from the initial pressure p1 to the
delivery pressure p2 is given by the equation (6.5):
𝑝2
(4.9)
𝑊𝑖𝑛𝑑𝑖𝑐𝑎𝑡𝑒𝑑 = ∫ 𝑣𝑑𝑝
𝑝1

Applying the equations (6.1) to (6.5) and using the ideal gas equation, we get
the equation for the indicated work:

 n −1
 (4.10)
 
p1v1   − 1

n p n
Win = 2
n −1  p1  
 

For the two-stage compressor, the total work done on the system is the sum
of the work done by each compressor.
37
Between Work and polytropic Power (Pp) is given by the relation:

𝑃𝑝 = 𝑚̇𝑊𝑖𝑛 (4.11)
Equation (6) is applied in (7) and using the ideal gas equation, we get:
𝑛−1 (4.12)
𝑛 𝑝2 𝑛
𝑃𝑝 = 𝑚̇𝑅𝑇 [( ) − 1]
𝑛−1 𝑝1

The polytropic efficiency of the compressor, 𝜂𝑃 :

𝑃𝑝 (4.13)
𝜂𝑃 =
𝑃𝑠

Where: Ps is the motor shaft power.

The compressor requires electrical power Pe to produce Ps.

𝑃𝑠 (4.14)
𝜂𝑚 =
𝑃𝑒

Where: 𝜂𝑚 is the motor efficiency. The value for 𝜂𝑃 = 98%, 𝜂𝑚 = 98%

can be used.

b. Heat Loss in the heat exchanger

The heat exchangers reject the heat produced in the air compressors. The total
heat absorbed by the cooling medium (water):

𝑄 = 𝑄1 + 𝑄2 (4.15)
𝑄 = 𝑚̇1 (ℎ𝑜𝑢𝑡,1 − ℎ𝑖𝑛,1 ) + 𝑚̇2 (ℎ𝑜𝑢𝑡,2 − ℎ𝑖𝑛,2 )

Applied this equation to our compressor, it becomes:

𝑄 = 𝑚̇1 (ℎ8 − ℎ7 ) + 𝑚̇2 (ℎ9 − ℎ7 ) (4.16)

. .
For m we use m =  W
38
ρ and W is the density and the mass flow rate of the water

c. Heat Loss in the compressor

From the first law of thermodynamics, the energy balance per mass in the
compressor with an assumption that the kinetic and potential energy change
is negligible follows the equation:

𝑞 − 𝑤 = ∆ℎ (4.17)

Rearranging this equation, we get the heat loss per unit mass in each
compressor:

𝑞 = ∆ℎ + 𝑤 = (4.18)

4.3 EXPERIMENTAL EQUIPMENT

Air compressor Model PCB 100 is used in this experiment. A schematic of the
air diagram PCB100 is shown in Figure 6.2 provided in Appendix A.

4.4 EXPERIMENTAL PROCEDURE

a. Ensure the cooling water flow rate is sufficient, approximately 100

L/H. Adjust it using the valves. Then connect the water inlet and
outlet properly.
b. Plug the flexible cable into diaphragm D1 for compressing air at p4
= 2.5 bar absolute.
c. Start the air compressor by turning on the main switch on the control
panel.
d. Record the data for suction conditions into the table datasheet, then
wait for about 10 minutes to get a steady-state condition.
e. Record the temperature and pressure value indicated in the column
‘first stage’ compression of the data sheet and wait for 5 minutes.
f. Fill up the values in the second state of the compression column
and wait 5 minutes for final compression.
g. Record the rest of the data in the datasheet.
h. Repeat step (a. until g.) for p4= 4 bar and p4 = 7 bar absolute by
replacing the cable flexible into diaphragm D2 and D3.

39
ACTIVITY 1

EXPERIMENTAL DATA

Refer to the datasheet provided in Appendix B.

RESULTS AND DISCUSSION

i. Draw the curve Q1 = f(β1), where β1 = p1/p0

ii. Draw the curve Q2 = f(β2) where β2 = p2/p1
iii. Calculate the polytropic coefficient n for this two-stage air compressor.
iv. Calculate the polytropic work for each p4 = 2.5,4 and 7 bar.
v. What is the polytropic efficiency of the air compressor  p ?
vi. Calculate the volumetric efficiency,  v ?

vii. Based on the value n at question 7(c) above, is it acceptable if we

assume that the compression process follows an adiabatic process?
Give reasonable arguments.
viii. Assume that the compression process shall be adiabatic. Then,
calculate the adiabatic efficiency, a ?

QUESTIONS

i. Is an air compressor considered a closed or open system? Explain it.

ii. Describe how a diaphragm works.
iii. What is the heat exchanger's function, and give an example of two
industries that use the equipment?
iv. How can we precisely measure the rotation speed of the motor?

CONCLUSION

Deduce conclusions from the experiment. Then, comment on your

experimental work in terms of achievement, problems faced throughout the
investigation, and recommendations for improvement.

REFERENCES
1. Cengel, Y.A. and Boles, M.A. (2011). Thermodynamics: An Engineering
Approach., 7th edition. New York: McGraw-Hill.
2. Sonntag, R.E. and Borgnakke C. (2007). Introduction to Engineering
Thermodynamics. 2nd edition. Hoboken, NJ: John Wile

40
 APPENDIX A

Figure 6.2: Schematic diagram of the air diagram PCB10

41
 APPENDIX B

TWO-STAGE AIR COMPRESSOR

DATASHEET:

No Item Characteristic Value Remarks

1 Motor Rotation speed 2880 rpm

2 Compressor First stage Diameter: 104.7 mm

Length: 55.5 mm
Clearance Volume: 4 cm3

Second stage Diameter: 54.7 mm

Length: 55.5 mm
Clearance Volume :
2.7cm3

3 Storage tank Capacity 2701

Ambie
Second State of Final
Pressure nt Air First State of Compression
Compression Compression
T1 T1 P2 T3
- P1- / T P T3 - /T
P4 T0 P0 T1 P1 T0 P0 T0 β1 2 T3 2 -T2 P1 2 T4 P3

2.5
4

Air flow
Input Exchange Exchange Exchange
Tank rate Air
Water circuit power water 1 water 2 water
Pressure temperature tank
( m 3 / h) (kW) inlet outlet outlet

P4 T5 W1 W2 V Pe T6 T7 T8 T9

2.5

42
 TOPIC 5

AIR CONDITIONING SYSTEM

TOPIC LEARNING OUTCOMES

At the end of this topic, students will be able to understand the air conditioning
processes for summer application qualitatively and quantitatively.

CONTENT

5.1 INTRODUCTION

Air conditioning is a combined process that performs many functions simultaneously.

It conditions air, transports, and introduces it to the conditioned space. Temperature
and humidity control and air movement are the most important actions in operating an
air conditioning system. All these factors have an important factor on human comfort.

5.2 EXPERIMENTAL THEORY

5.2.1 PSYCHROMETRIC CHART

A psychrometric chart is one of the charts that is commonly used in solving HVAC
problems. The properties of air such as wet bulb temperature, dry bulb temperature,
dew point temperature, relative humidity, humidity ratio, specific enthalpy, and specific
volume are shown on this chart.

5.2.2 REFRIGERATION PROCESSES

The most common summer air conditioning system application is to cool and
dehumidify the air. Hence, the operation principle of air conditioning processes is
similar to that of refrigeration, but the operating temperatures are different. In
refrigeration processes, heat is extracted from a lower-temperature heat source,

43
substance, or cooling medium (refrigerant) and transferred to a higher-temperature
heat sink. Refrigeration maintains the temperature of the heat source below its
surroundings while transferring the extracted heat to a heat sink or atmosphere air.

Figure 5.1: Illustration of simple vapour compression system

Figure 5.1 illustrates an air conditioning system that works on the vapor-compression
cycle. The heat and work interactions of the processes of the cycle are as follows:

i. Heat Q0 is absorbed in the evaporator by evaporating a liquid refrigerant at low

pressure and corresponding low saturation temperature.

ii. The evaporated refrigerant vapour is compressed to high pressure in the
compressor-consuming work ( W ).
iii. Heat Qk is rejected in the condenser to the surroundings at high temperatures.

5.2.3 COEFFICIENT OF PERFORMANCE (COP)

The performance of an air conditioning system is expressed by the ratio of proper heat
to work, called the energy ratio or coefficient of performance (COP):
𝑄0 (5.1)
𝐶𝑂𝑃 =
𝑊

44
The relationship between the heat absorbed and rejected from the system and the
work is:
𝑄𝐾 = 𝑄0 + 𝑊 (5.2)

Calculating COP is convenient for representing the refrigeration cycle on the p-h
diagram, as shown in Figure 5.2.

The cycle described in Figure 5.2 is a simple saturation cycle implying that both the
states of liquid after condensation and vapour after evaporation are saturated and lie
on the saturated liquid and saturated curves, respectively. Therefore, the COP
expressed in enthalpy form is:
ℎ1 − ℎ4 (5.3)
𝐶𝑂𝑃 =
ℎ2 − ℎ1

Figure 5.2: Refrigeration cycle on the p-h diagram

5.2.4 HUMIDIFICATION

When air is heated, it can absorb more water vapour. A humidifier can then increase
and control moisture in the air. Humidification adds water vapour (low-temperature
steam) to the air. In humidification, the humidity ratio of the air space increases,

45
therefore, its relative humidity. A critical index of a humidifier is its capacity or the rate
at which water vapour is added to the air (an increase of moisture content). It can be
calculated using the following relation:
∆𝑚 = 𝜌𝑉 (𝜔𝑠 − 𝜔𝑚 ) (5.4)

Where:

m : Increase of moisture content, [kg/s]


V : Supply volume flow rate, [m3/s]
 : Density of supply air, [kg/m3]

 s , m : Moisture content of supply and mixture air, respectively


The value V can be calculated as follows:
𝑉 = 𝜌𝐴𝑢 (5.5)

Where:

A : Duct cross-section area, [m2]

u : Air velocity, [m/s]

5.2.5 AIR FLOW MEASUREMENT

The air velocity, u can be calculated using Bernoulli’s equation:

𝜌1 𝑢12 𝜌2 𝑢22 (5.6)
𝑃1 + = 𝑃2 +
2 2

The subscripts 1 and 2 are referred to as the inlet and outlet of the airflow within the
duct. Rearranging the equation, it becomes:

𝜌2 𝑢22 𝜌1 𝑢12 (5.7)

𝑃1 − 𝑃2 = Δ𝑃 + −
2 2

46
The value p can determine using a water manometer.
Δ𝑃 = 𝜌𝑔ℎ (5.8)

Where:
 : Density of water, [kg/m3]
g : Gravity constant, [m2/s], and
h : Velocity pressure in inches of water, [m].

5.3 EXPERIMENTAL EQUIPMENT

Air Conditioning Laboratory Trainer RAD-ACL-1 is shown in Figure 5.3.

Figure 5.3: Air Conditioning Laboratory Trainer RAD-ACL-1

5.4 EXPERIMENTAL PROCEDURE

47
5.4.1 PRE-OPERATION

a. Check the refrigerant pressure by observing the pressure gauges. When the
system is not active in the balance condition, the normal pressures should be
145 PSIG (1 bar = 14.5 PSIG) at the suction and discharge.
b. Ensure that the steam generator water inlet is connected to the water source
and the water tank is filled with fresh water for approximately 19 liters.
c. Fill the water reservoirs on the wet bulb sensors with distilled water.
d. Set the manometer to zero scales by turning the zero set.
e. Ensure selector switches (steam generator, pre-heater, re-heater, and
compressor) on the control panel are in the OFF position.
f. Ensure that thermostats (steam generator, pre-heater, and re-heater) are
adjusted to 0oC.
g. Switch ON all of the circuit breakers (F1-F10).

5.4.2 EXPERIMENT 1: OPERATION FOR CALCULATING COP AND ENTHALPY

CHANGE RATE OF AIR AND REFRIGERANT

a. Press the “START” push button on the control panel box.

b. Turn ON and adjust the fan speed to the maximum position by turning the fan
speed control.
c. Set the thermostat pre-heater and re-heater to 50oC – 60oC.
d. Adjust the pre-heater switch to 1 kW of power usage.
e. Adjust the re-heater power switch to 0.5 kW of power usage.
f. Switch ON the compressor power and let the system run for about 15 minutes.
g. When the system is running, observe and record the following conditions in
Table 5.1.
h. After completing the observation, switch OFF the pre-heater, re-heater, and
compressor.
i. Let the fan run for about 5 minutes to circulate the air, and press the STOP push
button.
j. Use the pressure-enthalpy diagram to complete the result data in Table 5.2.

48
5.4.3 EXPERIMENT 2: OPERATION FOR COOLING AND HUMIDIFYING
PROCESSES

After completing experiment 1, do the following steps to experiment 2.

a. Press the “START” push button on the control panel box.

b. Set the steam generator thermostat to 105oC.
c. Turn ON and adjust the fan speed to the maximum position by turning the fan
speed control.
d. Adjust the steam generator switch to 5kW of power usage and allow it is working
for about 20 minutes.
e. Observe and record the following in Table 5.3.
f. After completing this experiment, switch OFF the steam generator switch and
adjust the corresponding thermostat to 0oC.
g. Let the fan run for about 5 minutes to circulate the air, and press the STOP push
button.

ACTIVITY 1

EXPERIMENTAL DATA

Refer to the datasheet provided in Appendix A.

RESULTS AND DISCUSSION

a. Complete Tables 5.1, 5.2, and 5.3 provided in Appendix A.

b. Use the p-h diagram and psychrometric chart to plot the result from
Experiment 1.
c. What is the COP of the air conditioning unit?
d. What is the enthalpy change rate of air?

Answer the following questions based on Experiment 2:

a. What is the increase/decrease of the moisture content in the air stream?

49
 b. What is the relative humidity change if the dry bulb and wet bulb temperatures
increase more than before?
QUESTIONS

a. Describe the function of the pre-heater and re-heater used in this experiment.
b. What are the advantages/disadvantages of refrigerants R22 and R134a?

CONCLUSION

Deduce conclusions from the experiment. Please comment on experimental work

regarding achievement and problems faced throughout the experiment and suggest
recommendations for improvements.

REFERENCES

1. Cengel, Y.A. and Boles, M.A. (2011). Thermodynamics: An Engineering

Approach., 7th Edition. New York : McGraw-Hill.
2. Sonntag, R.E. and Borgnakke C. (2007). Introduction to Engineering
Thermodynamics. 2nd edition. Hoboken, NJ : John Wiley.
3. Moran M.J and Shapiro H.N. (2010). Fundamentals of Engineering
Thermodynamics. 6th Edition. Hoboken, NJ : John Wiley.

50
 APPENDIX A
AIR CONDITIONING SYSTEM

- DETERMINATION OF COP -
DATASHEET:

Table 5.1 Pressure and Temperature Measurements

No. Measurement Point Value Unit

1 Discharge pressure PSIG
2 Suction pressure PSIG
o
3 Before condenser temperature (5A) C
o
4 After condenser temperature (6A) C
o
5 Before TXV temperature (7A) C
o
6 After evaporator temperature (8A) C
o
7 Before compressor temperature (9A) C

Table 5.2 Thermodynamic Properties of the refrigerant in the system

No. Measurement Point Value Unit

1 Discharge pressure MPa
2 Suction pressure Mpa
3 Start compressing enthalpy point (h1) kJ/kg
4 Start condensation enthalpy point (h2) kJ/kg
5 End condensation enthalpy point (h3) kJ/kg
6 Start evaporation enthalpy point (h4) kJ/kg

Table 5.3 Humidifying

No. Measurement Point Temperature [oC] Value

T1A dry bulb
1 Inlet air
T1B wet bulb
T2A dry bulb
3 After pre-heater
T2B wet bulb

51
APPENDIX A

Figure 5. 4: SI ASHRAE Psychrometric Chart

52
 APPENDIX A

Figure 5.5: Pressure-Enthalpy Diagram for Refrigerant 22

53
 TOPIC 6
COOLING TOWER UNIT
TOPIC LEARNING OUTCOMES
At the end of this topic, students will be able to:
I. Study the basic principles and characteristics of the evaporative water
cooling tower system.
II. Investigate the efficiency of cooling tower performance.

CONTENT
6.1 INTRODUCTION
A cooling tower is a heat exchanger in which air and water are allowed to come
into direct contact to lower the water temperature. Air enters the tower from
below the fill and is drawn upwards into the tower. Low-pressure spray nozzles
are used to put hot water above the fill. The hot water is then spread out over
the surface of the filling in small droplets. As the air flows down the tower, it
cools the water, dissipating the heat it had absorbed from the air, as shown in
Figure 6.3.

Figure 6.3: Basic principle of cooling tower (Ref:

https://en.wikipedia.org/wiki/Cooling_tower)
This experiment demonstrates a modern evaporative cooling system's
building, design, and functioning. The test unit is also a great example of an
"open system" because it has two fluid streams (water and air) and a mass
54
transfer from one stream to the other. Figure 6.4 is the overall balance of the
heat exchanged in the cooling tower, and Figure 6.5 represents the test unit's
schematic representation.

T4
T3
Qwater
Rh3

Cooling
Tower

QAir
T2
T5
Rh2

Figure 6.4: Overall balance of the heat exchanged in the cooling tower.

6.2 EXPERIMENTAL THEORY

6.2.1 Basic Principle

First, consider an air stream passing over the surface of a warm water droplet
or film. If we assume that the water is hotter than the air, the water temperature
will be cooled down by radiation, conduction and convection, and evaporation.
The radiation effect is usually minimal and may be neglected. Conduction and
convection depend on the temperature difference, the surface area, air
velocity, etc. The effect of evaporation is the most significant where cooling
occurs as water molecules diffuse from the surface into the surrounding air.
During evaporation, the water molecules in the liquid from which the needed
energy is extracted are replaced by other molecules.

55
6.2.2 Cooling Tower Performance

A study on the performance of a cooling tower can be done with the help of a
benchtop unit. Students shall be able to verify the effect of these factors on the
cooling tower performance:
I. Water flow rates
II. Water temperatures
III. Airflow rate
IV. Inlet Air Relative Humidity
The effect of these factors will be studied in depth by varying it. As a result,
students will gain an overall view of the cooling tower operation.

To understand the working principle and performance of a cooling tower, a

basic knowledge of thermodynamics is essential to all students. The water
enters the top cooling tower at a flow rate, Q water (m3/h), and a temperature of
T4, as shown in Error! Reference source not found. T5 is a water outlet from
the cooling tower. The air inter the tower at T2 with relative humidity (Rh2) and
flow rate (Q air). Then, the air outlet (T3) with relative humidity (Rh3) from the
tower to the ambient. T2 and T3 represent the dry bulb temperature with the
relative wet bulb values (T2a and T3a).

The quantity of heat discharged by the water (H) is given by:

𝐻 = 𝑄𝑤𝑎𝑡𝑒𝑟 . 𝜌𝑤𝑎𝑡𝑒𝑟 . 𝑐𝑝 . (𝑇4 − 𝑇5 ) 𝑘𝐽⁄ℎ (6.19)

Where: Qwater = water flow rate (m3/h)

ρwater = water density (kg/m3)
cp = Specific heat (4.18 kJ/kg. K)
T = Temperature (K)
In ideal conditions, the air entirely takes overheat (H). But in practice, the air
absorbs only a certain proportion of it.

56
Figure 6.5: Schematic diagram for Cooling Tower study unit.
57
 LEGEND PRESSURE
P0 – Pressure in the environment
A - Bottom support with air/water separation P1 – Pressure at head
chamber P2 – Pressure of air leaving the tower
P3 – Pressure of air entering the tower
B – Cooling Tower P0 – P1 = Air flow-rate different
P2-P3 = Load loss different
C – Centrifugal fan with air flow –rate choke

D – Electric heater for intake air LC = Minimum level control

TC – Automatic temperature control
E – Differential micro manometer RH – Water heating
RA - Air heating
> Air –Flow rate in the tower = P0–P1
1 – Discharge valve
> Load losses = P2 – P3 2 – Float Valve
3 – By-pass Valve
F- Water drop distributor head. 4 – Centrifugal circulation Pump
5 – Water flow-rate meter
G – Control Board.

H - Feed water transparent tank (10 L)

I - Tank to collect the water.

6.2.3 Thermodynamic Property

A brief review of some of the thermodynamic properties is presented below.

At the triple point (i.e., 0.00602 atm and 0.01°C), the specific enthalpy of
saturated water is assumed to be zero, which is taken as the datum. The
specific enthalpy of saturated water (hf) at a range of temperatures above the
datum condition can be obtained from thermodynamic tables.

The specific enthalpy of compressed liquid is given by

ℎ = ℎ𝑓 + 𝑣𝑓 ( 𝑝 − 𝑝𝑠𝑎𝑡 ) (6.20)

58
The correction for pressure is negligible for the operating condition of the
cooling tower; therefore, we can see that h ≈ hf at a given temperature.

Specific heat capacity (Cp) is the rate of change of enthalpy concerning

temperature (often called the specific heat at constant pressure). For the
experiment using a bench top cooling tower, we may use the following
relationship:
∆ℎ = 𝑐𝑝 ∆𝑇 (6.21)
and
ℎ = 𝑐𝑝 𝑇 (6.22)

6.2.4 Dalton’s and Gibb's Laws

It is commonly known that air consists of a mixture of "dry air" (O2, N2, and
other gases) and water vapour. Dalton’s and Gibb’s law describes the
behaviour of such a mixture as:
a) The total air pressure equals the sum of the pressures at which "dry
air" and water vapour exist. So they would exert alone if they occupied
the volume of the mixture at the temperature of the mixture.
b) The dry air and the water vapour respectively obey their normal property
relationships at partial pressures.
c) The enthalpy of the mixture may be found by adding together the
enthalpies. The dry air and water vapour each would have as the sole
occupant of the space occupied by the mixture and at the same
temperature.

The formula of absolute or Specific Humidity is as below:

𝑀𝑎𝑠𝑠 𝑜𝑓 𝑊𝑎𝑡𝑒𝑟 𝑉𝑎𝑝𝑜𝑢𝑟 (6.23)
𝑆𝑝𝑒𝑐𝑖𝑓𝑖𝑐 ℎ𝑢𝑚𝑖𝑑𝑖𝑡𝑦, 𝜔 =
𝑀𝑎𝑠𝑠 𝑜𝑓 𝐷𝑟𝑦 𝐴𝑖𝑟

The relative humidity is defined as below:

59
 𝑅𝑒𝑙𝑎𝑡𝑖𝑣𝑒 ℎ𝑢𝑚𝑖𝑑𝑖𝑡𝑦, ∅ (6.24)
𝑃𝑎𝑟𝑡𝑖𝑎𝑙 𝑝𝑟𝑒𝑠𝑠𝑢𝑟𝑒 𝑜𝑓 𝑊𝑎𝑡𝑒𝑟 𝑉𝑎𝑝𝑜𝑢𝑟 𝑖𝑛 𝑡ℎ𝑒 𝑎𝑖𝑟
=
𝑆𝑎𝑡𝑢𝑟𝑎𝑡𝑖𝑜𝑛 𝑝𝑟𝑒𝑠𝑠𝑢𝑟𝑒 𝑜𝑓 𝑊𝑎𝑡𝑒𝑟 𝑉𝑎𝑝𝑜𝑢𝑟 𝑎𝑡 𝑡ℎ𝑒 𝑠𝑎𝑚𝑒 𝑡𝑒𝑚𝑝𝑒𝑟𝑎𝑡𝑢𝑟𝑒

The Percentage Saturation is defined as follows:

𝑃𝑒𝑟𝑐𝑒𝑛𝑡𝑎𝑔𝑒 𝑆𝑎𝑡𝑢𝑟𝑎𝑡𝑖𝑜𝑛 (6.25)
𝑀𝑎𝑠𝑠 𝑜𝑓 𝑊𝑎𝑡𝑒𝑟 𝑉𝑎𝑝𝑜𝑢𝑟 𝑖𝑛 𝑎 𝑔𝑖𝑣𝑒𝑛 𝑉𝑜𝑙𝑢𝑚𝑒 𝑜𝑓 𝐴𝑖𝑟
=
𝑀𝑎𝑠𝑠 𝑜𝑓 𝑡ℎ𝑒 𝑠𝑎𝑚𝑒 𝑣𝑜𝑙 𝑜𝑓 𝑆𝑎𝑡 𝑊𝑎𝑡𝑒𝑟 𝑉𝑎𝑝𝑜𝑢𝑟
𝑎𝑡 𝑡ℎ𝑒 𝑠𝑎𝑚𝑒 𝑇𝑒𝑚𝑝𝑎𝑟𝑎𝑡𝑢𝑟𝑒

At high humidity conditions, it can be shown that there is not much difference
between the "Relative Humidity" and the "Percentage Saturation"; thus, we
shall regard it as the same.

This benchtop cooling tower unit is supplied with electronic dry bulb and wet
bulb temperature sensors to measure the atmosphere's moisture content. The
temperature readings shall be used in conjunction with a psychometric chart.

6.2.3 Psychrometric Chart

The psychometric chart is suitable for determining the properties of the

air/water vapour mixture. Among the properties that can be defined with a
psychometric chart are Dry Bulb Temperature, Wet Bulb Temperature,
Relative Humidity, Humidity Ratio, Specific Volume, and Specific Enthalpy. In
addition, other properties can be easily identified from the chart, provided the
air pressure is approximately atmospheric.
In the Bench Top Cooling Tower application, the air inlet and outlet
sensor show the dry bulb and wet bulb temperature. Therefore, the
psychometric chart can readily read the specific enthalpy, specific volume,
humidity ratio, and relative humidity.
The psychometric chart provided with this manual is only applicable for
atmospheric pressure operating conditions (1.013 bar). However, the error
resulting from the variation of local atmospheric pressure is typically negligible
up to altitudes 500m above sea level.
60
 To determine the relative humidity of an environment, take the
temperature read on the dry-bulb thermometer and subtract it from the
temperature read on the wet-bulb thermometer. Then, consult a chart of
relative humidity readings as shown in Figure 6.6. An example, if the dry bulb
temperature is 20oC and the wet bulb temperature is 15oC. So, the relative
Humidity (Rh) is 60%.

Figure 6.6: Plot of Dry bulb and Wet bulb temperatures (Ref:
https://www.sciencedirect.com/topics/engineering/psychrometric-chart ).

In ideal conditions, the quantity of heat discharge by water (H) is entirely taken
over by the air. But, in actual practice, the air absorbs only a certain proportion
of it. For example, consider the psychrometric chart illustrated in Figure 6.7;
T2, Rh2, T3, and Rh3 can be measured. Points A and B denote the input and
output air with the enthalpy values hA and hB, respectively.

Hence, the total heat absorbed by the air will be:

ℎ′ = ℎ𝐴 − ℎ𝐵 [𝑘𝐽⁄𝑘𝑔] (6.26)

Which, transformed into heat potential, becomes:

61
 𝐻 ′ = (ℎ𝐵 − ℎ𝐴 ) × 𝜌𝐴𝑖𝑟 × 𝑄𝐴𝑖𝑟 [𝑘𝐽⁄ℎ] (6.27)

The density of the air (ρair) can be read on the psychometric chart (determining
the reciprocal value of a specific volume, (m3/kgd.a) at output conditions: or, for
greater accuracy, at a mean value between specific volume in A and B.
Water cools down because the heat is discharged through convection and
through the evaporation of the water itself (seen in Figure 6.7). As a result, the
air passes from an absolute humidity value of w2 to a higher than w3.

Rh3

w3

Rh2

w2

T2 T3

Figure 6.7: Heating of the air in the cooling tower.

At the same time, the air acquires a sensible heat, hs, and latent heat, hL.

ℎ𝑠 = ℎ𝐶 − ℎ𝐴 [𝑘𝐽⁄𝑘𝑔] (6.28)

ℎ𝐿 = ℎ𝐵 − ℎ𝐶 [𝑘𝐽⁄𝑘𝑔] (6.29)

Evaporation is the primary path to cool down the working fluid. Therefore,
evaporation loss usually represents the cooling tower's efficiency and
equipment's heat. There is a formula to calculate evaporation loss volume:

62
Evaporation loss can also be expressed by using this formula:

𝑄𝑤𝑎𝑡𝑒𝑟 × (𝑇4 − 𝑇5 ) × 𝐶𝑃 𝑚3 (6.30)

𝐸= [ ⁄ℎ]
ℎ𝐿

Where:
Cp = specific heat of water = 1 kcal/kg / °C (or) 4.184 kJ / kg / °C
The efficiency of the cooling towers will typically range from 65 to 70%.
However, the efficacy of cooling towers is limited in the summer because the
ambient air wet bulb temperature is higher in the summer than in the winter.

Cooling tower efficiency, becomes:

𝐶𝑜𝑜𝑙𝑖𝑛𝑔 𝑡𝑜𝑤𝑒𝑟 𝑒𝑓𝑓𝑖𝑐𝑖𝑒𝑛𝑐𝑦, 𝜂𝑒𝑓𝑓. (6.31)

(𝐶𝑜𝑜𝑙𝑖𝑛𝑔 𝑡𝑜𝑤𝑒𝑟 𝑖𝑛𝑙𝑒𝑡 𝑤𝑎𝑡𝑒𝑟 𝑡𝑒𝑚𝑝. −𝐶𝑜𝑜𝑙𝑖𝑛𝑔 𝑡𝑜𝑤𝑒𝑟 𝑜𝑢𝑡𝑙𝑒𝑡 𝑤𝑎𝑡𝑒𝑟 𝑡𝑒𝑚𝑝. )
=
(𝐶𝑜𝑜𝑙𝑖𝑛𝑔 𝑡𝑜𝑤𝑒𝑟 𝑖𝑛𝑙𝑒𝑡 𝑤𝑎𝑡𝑒𝑟 𝑡𝑒𝑚𝑝. −𝑊𝑒𝑡 𝑏𝑢𝑙𝑏 𝑡𝑒𝑚𝑝. )
× 100

(𝑇4 − 𝑇5 )
𝜂𝑒𝑓𝑓. = × 100
(𝑇4 − 𝑇3𝑎 )

6.3 EXPERIMENTAL PROCEDURE

6.3.1 General Start-up Procedures
i. Ensure all valves are closed, and the pump bypass valve (3) is
opened.
ii. Fill the load tank with distilled or deionized water. Fill the tank with
distilled or deionized water up to 30 cm on the level scale.
iii. Add distilled/deionized water to the wet bulb sensor reservoir to
the fullest (T2a and T3a).
iv. Connect all appropriate tubing to the differential pressure sensor.
v. Install the appropriate cooling tower packing for the experiment.

63
 vi. Then, set the temperature set point of the temperature controller
to 50°C. Next, switch on the 3.0 kW (RH1 and RH2) water heater
and heat the water.
vii. Switch on the pump, slowly open the control valve V1, and set the
water flow rate to 100 LPH. Obtain a steady operation where the
water is distributed and flowing uniformly through the packing.
viii. Fully open the fan damper, and then switch on the fan to maximum
speed. Check that the differential pressure sensor reads when the
valve manifold is changed to measure the orifice differential
pressure.
ix. Let the unit run for about 20 minutes for the float valve to adjust
the load tank's level correctly. Then, refill the makeup tank as
required. Now, the unit is ready for use.

Note:
a. It is strongly recommended that ONLY distilled or deionised
water be used in this unit. This is because the impurities
existing in tap water may cause the depositing in the cover
tower.
b. Check that the pressure tubing for differential pressure
measurement is connected correctly. (Orifice pressure
tapping point to V4; Column’s lower pressure tapping point
to V6; Column’s higher pressure tapping point to V3; V5
leave to atmosphere)
c. To measure the differential pressure across the orifice, open
valves V4 and V5; close valves V3 and V6.
d. To measure the differential pressure across the column,
open valves V3 and V6; close valves V4 and V5.
e. Always ensure no water is in the pressure tubing for accurate
differential pressure measurement.

64
6.3.2 General Shut-Down Procedure
i. Switch off heaters and let the water circulate through the
cooling
tower system for 3-5 minutes until the water cooled down.
ii. Switch off the fan and fully close the fan damper.
iii. Switch off the pump and power supply.
iv. Retain the water in the reservoir tank for the following
experiment.
v. Completely drain the water from the unit if it is not in use.

6.4 RESULTS (15%)

a. Calculate and fill Table 6.1, Table 6.2, and Table 6.3 in Appendix.
b. Plot suitable value for Table 6.3 in Figure 6.8.
c. Plot graph for cooling tower efficiency against Air Flow rate

6.5 Observation (25%)

You need to observe the experiment that you have conducted.

6.6 Calculation (10%)

Show your calculation.

6.7 DISCUSSION (30%)

a. Discuss the result from the graph.
b. What suggestions do you have to improve the experiment?
c. Discuss the heat discharge by water (H), heat absorbed by the air (h'),
Sensible heat (hs), and Evaporation Loss (E) in this experiment.
d. Describe the significance of the cooling tower efficiency for the cooling
tower system.

6.8 Conclusion (15%)

Deduce the conclusion from the experiment. Then, comment on your
experimental work regarding the achievement and the problem faced
throughout the experiment and suggest improvement recommendations.
65
REFERENCES

4. Cengel, Y.A. and Boles, M.A. (2011). Thermodynamics: An Engineering

Approach., 7th Edition. New York : McGraw-Hill.

66
 APPENDIX A
COOLING TOWER SYSTEM

DATASHEET:
Table 6.1: Basic Water Cooling Tower Observation Sheet
Initial water level : _______ cm
Final water level : _______ cm
Start time : _______ minutes
End time : _______ minutes
Diameter of wire mesh Centrifugal fan: ______ cm

No. Test number 1 2 3

1. Blower velocity, Vread (m/s)

2. Ambient Temperature, T1
3. Air inlet Dry Bulb, T2.
4. Air inlet Wet Bulb, T2a.
5. Air Outlet Dry Bulb, T3.
6. Air Outlet Wet Bulb, T3a.
7. Water inter temperature, T4.
8. Water out temperature, T5.
9. Water inter the collection
tank, T6.
10. Feed water temperature, T7.
11. Orifice differential, ∆p
(mmH2O).

12. Water flowrate, Qwater (L/h) 100 100 100

13. Heat Power, (RH 1+ RH2 ) 3 kW 3 kW 3 kW
watt

67
 Table 6.2: Cooling Tower Result
Test Air Inlet Absolute Outlet Absolute Heat Heat Sensible Latent Evaporation Cooling
Number Flow Relative humidity, Relative humidity, Discharge absorbed heat, hs heat, Loss. E tower
rate, humidity W2,gw/kg da humidity W3,gw/kg da by water, by the (kJ/kg) hL (m3/h) efficiency,
QAir (Rh2) (Rh3) H (kJ/h) air, h' (kJ/kg) %, 𝜼
(m3/h) (kJ/kg)
1

Table 6.3: Results from Psychometric chart

Test Inlet Absolute Outlet Absolute Specific Specific Mean Air
Number Relative humidity Relative humidity, volume at volume Specific density,
humidity at T2, humidity at T3, T2, at T3, volume, 𝝆𝒂𝒊𝒓 ,
𝟑 𝟑 𝟑 𝒌𝒈⁄
(Rh2) w2,gw/kg da (Rh3) w3,gw/kg da 𝒎
𝝊𝟐 , ⁄𝒌𝒈 𝝊𝟑 , 𝒎 ⁄𝒌𝒈 𝝊, 𝒎 ⁄𝒌𝒈
𝒎𝟑
1

68
Figure 6.8: SI ASHRAE Psychrometric Chart
69