MANIPAL INSTITUTE OF TECHNOLOGY

PINI
MANIPAL

DEPARTMENT OF MECHANICAL AND MANUFACTURING

ENGINEERING

2nd Semester MTech (ThermalSciences &

Energy Svstems)

RENEWABLE ENERGY LABORATORY

(MME 5265)

MANUAL BOOK

NAME Rutura Avind UmaranikaT

ROLL NO

REGISTER NO : 20097 900g

MIT/MME/RENEWABLE ENERGY LAB MNL/02

 sPIRT MANIPAL INSTITUTE OF TECHNOL0GY

Manipal Academy of Higher Education, Manipal -

576104

DEPARTMENT OF MECHANICAL & MANUFACTURING ENGINEERING

CERTIFICATE

This is to certify that Ms. /Mr. ...Rutura..A:vind.. Umaranikar.. *************************|

Reg. No. 200979001.Roll No.: .

**********
*********
has satisfactorily completed the

course of exercises in RENEWABLE ENERGY LABORATOR Y (MME 5265) prescribed

by the Manipal Academy of Higher Education for M Tech (Thermal Sciences & Energy

Systems) at MIT, Manipal.

Date: 0o7|202|

Signature Signature
Faculty in Charge Head of the Department
2nd Semester M. Tech- Thermal Sciences &
Energy Systems
RENEWABLE ENERGY LABORATORY (MME 5265)
CONTENTS

SI Name of the CO Page Marks

No. Experiment Addressed No. (10)
Photovoltaic module demonstrator 04 02
2 Wind energy training system 04 10 7
3 Solar air dryer 02 18
4 Photovoltaic training system 05 28 7.S
5 Paraboloid solar concentrator 03 40 7.5
6 Paraboloid solar cooker 03 48 7.5
7 Flatplate solar water heating system 02 60 8
8 Evacuated tube solar water heater 02 74 8
9 Thermal energy storage system 01 82 9
10 Solar box cooker 02 100
TOTAL G4

Faculty In charge
s n rays

Qs recenver (O

two-axes trackimg
mechanism

40
 5 Date:- 25los/2021
PARABOLOID SOLAR CONCENTRATOR
AIM:
To determine the thermal efficiency, optical efficiency and receiver efficiency of a Paraboloid solar

concentrator.

THEORY:
Solar Thermal Systems can be Flat Plate type (for low temperature ranges) or Concentrator type (for
medium and high temperature ranges), which show considerable potential as best options to

overcome the energy crisis / problems. Solar thermal power systems utilize the heat generated by
concentrating and absorbing incident solar energy to drive a heat engine. generator and produce

electric power. Three generic solar thermal power systems, trough, power tower, and dish systems,
are being employed for power production. Trough systems use linear parabolic concentrators to

focus sunlight along the focal lines of the collectors. In a power tower system, a field of two-axis
tracking mirrors, called heliostats, reflects the solar energy onto a receiver that is mounted on top of
a centrally-located tower. Dish systems, the third type of solar thermal power system, comprise a

parabolic dish concentrator, a thermal receiver, and a suitable working fluid. Dish systems can have
concentration ratio of about 75 and operate at temperatures of around 400°C. A number of
thermodynamic cycles and working fluids have been considered for dish systems. These include
Rankine cycle, using water or an organic working fluid; Brayton cycle and Stirling cycle. Among
these, Stirling engines have been mainly used with recorded efficiency of around 30 %.
The collector thermal efficiency (7un) is defined as the ratio of the useful energy delivered (Q.) to the
energy incident on the concentrator aperture (Q). Under steady state conditions, the useful heat
delivered by a solar collector system is equal to the energy absorbed by the heat transfer fluid, which
is determined by the radiant solar energy falling on the receiver (O) minus the direct or indirect heat
losses from the receiver to the surroundings (O).

The radiation falling on the receiver is a function of the optical efficiency (n) which is defined as
the ratio of the energy falling on the receiver to the energy incident on the concentrator's aperture.
The receiver efficiency (7) is defined as the ratio of the useful energy delivered to the energy falling
on the receiver. Hence the thermal efficiency can be expressed as:

nth = no.r
Qs (1)

TchToo-( (2)
Thermal efficiency is also defined as:

41
 nth
(rnCp)wdT
IpAp (3)
Total heat loss from system to
surrounding is:
Q= + 0, +Q
(4)
The total heat transfer
(convective +
radiative) from bottom, side and top surface can be calculated
IS:

= [hA,(T,-Ta)+aA,e(T$ -T;) 5)
, =
[h4,(T -Ta)l +
oA,E(Ta-T#) (6)
Q [hA (T-Ta)] + oA,E(T? - Tsky)
=

(7)
Where, h =
8.55+2.56 VW/mK, Tz, Tsd and T are the bottom, side and top surface temperature
of the vessel. is the
"T, reflector surface temperature. Tsky' is sky temperature (Ta 6) considered
-

in radiation heat transfer.

EXPERIMENTAL SET UP:

It consists of a
paraboloid concentrator with stand and provision for orientation. A black coated
absorber is placed at the focal point of the concentrator. There are four
thermocouples to measure
water in and out
temperature, absorber bottom surface temperature and reflector surface
temperature.
A digital
weighing scale, flask and stop watch are used to measure the mass flow rate of water
through the absorber. Anemometer and solar flux meter are used to measure wind
velocity and solar
radiation level respectively.

SPECIFICATIONS:
1. Concentrator:
Aperture diameter : 1000 mm
Focal length :405 mm
Reflector material SS sheet having reflectivity of over 80%.
2. Absorber:
.Aluminium darkened surface (2 litre capacity)
3. Thermo couples :4 Nos, Cr-Al

4. Panel
Mains switch :Rocker type, DPST with illumination, 16 A
Temperature :Digital 0 -999° C, 4 channel
PRECAUTIONS:
. Properly connect the power supply.
2. Operate selector switch of temperature indicator gently.

42
PROCEDURE:
1. Arrange the solar paraboloid concentrator in the required orientation.
2. Maintain the constant water flow rate through the absorber.

3. Switch on the digital indicator.

4. Note down the solar radiation level (beam radiation), water flow rate, wind velocity, water

inlet (Ti) and outlet (T2) temperatures, reflector surface temperature (T3) and absorber
bottom surface temperature (Ta) once in every 15 minutes.

5. Continue the experiment till maximum outlet temperature of water is recorded.

6. After the test, unplug the electrical connection.
7. Various energy parameters are calculated to evaluate the performance of paraboloid
concentrator.

OBSERVATIONS:
Aperture area ofthe concentrator, Ap =0.1854m2
Total surface area of an absorber, As =0-123 m
Absorber base area, Ab = 0.022m2
Mass of the Absorber, mu 1.25 kg
Emissivity of vessel surface, E 0.20
Thermocouple readings (°C) Solar radiation Wind
Water mass
. Time Water Reflecto Absorber flow rate (W/m) Velocity
No. r bottom V
Inlet Outlet mw
(T:) (T4) (kg/s) l (m/s)
(T)(T)
9S 253 23 S 4-7 6 00SC|788 G98
2 10:5S 30-6 3 5 s 5 5 7 G9.4 o.00S 8So 10 0 T5
3 125 29.9 34.8 G5 37 G150.0Sc 1 106|810O
411:4O 8o 85.8S
G9.6 0.cos145 117 828
s12:25 31-8 382S19 GG O-oSC.|aG7 103 |364| o

12:480.2 98.SS4 656 O-o0Sc99 117 382 Op

CALCULATIONS:
1. Concentration ratio, C = Ap/Ap

2. Thermal efficiency, 7th (rnCp)wdT

IbAp
3. Totalheatloss, Q1 [hA,(T, -Ta]+oA,e(T- T#)
= W
4. Optical efficiency, 7o = Mth .

Qs
5. Receiver efficiency,n= th
o
6. Graph, Time of the day vs Thermal efficiency/ solar radiation
43
 Receiver
TABULATIONS:
Thermal Optical
Input heat Total heat
efficiency
yefficiency
efficiency
Solar
loss rate
beam rate

% %
Time radiation %
S. W W
No.
W/m
Nth No
21-2 62-9
S49.21 43.00 13.3
eg:1S698 TO-3
70.3
2 J0:55 750 S8t.0547.245|
43-1591.6 24.4, 721
L:25816 636.114 27.77% 73.4
G50.311249.929 20.
411:40 828 17.3
5 125 8G4 678.586| 42827 21S 27.2%
G c%| 78-0
612 40 882 Cg2.9228 4OS6120.7
RESULT The energy parameters of paraboloid concentrator are:

Concentration ratio, C = 83.95344

(1)
21:S
(2) Highest thermal efficiency, neth
=

(3) Average optical efficiency, 7o 18-82%

(4) Average receiver efficiency, 7, = g9. G%

(5) Maximum uncertainty in thermal efficiency, U7th =

38-37 %

CONCLUSION: ds
e
Thermatsicency icreds
d +htTe s
op ic efaeney j cT a s l s provsde
min oSSes.
QUESTIONS:
(1) Discuss the mathematical expression to calculate focal point.
(2) What is the significance of optical efficiency?
(3) What is the relation between optical and thermal efficiency?
(4) Explain the concept of line and point focusing with examples.
(5) What is the significance of reflector temperature in the thermal analysis?

GRAPH:

44
 SPECIMEN CALCULATION: Including uncertainty analysis
Trial number: 1

CC -33.353 45 =C
mCp dT o.60 S6 x 4071G (25-253 n
9 8 X O.1854
Ap
Leh 9. 3%

9, hAs (Ts-Ta) +TAa t (TT)

(i894472618
+)508xjo
-1371S (35.3)

= 43.006 wv
1 3 . 3

4-3.00 o
4 + / - 3 . 0 0 6

x100
13.3 t s43.209/
th *
E7 n -21.27,
3.3 G2.9%
21.2

ysis
Uncertainity Anal UdT o-1e IWm2
0.0|9/s
Take YTOr m
(4)
Ap) Ap
e n b (m,dT, Ib,
,

U mm

Uncestainily in anea Ap d
2

4
45

x (11?a 1 5 7X1-UAp
(
Uneerian y nth nah
2

A 4/2

4-71X3 2
G9No-7RS4X0*91+/256 X40T1: y o0 1 -0056x40716x 3.2
638xo-7854 GRn.7 854
G18x 0.7854 XI
0-09 SG X41)16 Xxa2 X1.57X10
G98X0.7854 1.57X10

0-2377 23-17

ANSWER:

fatal point calcudahon

D o c a length
D A peT}ure di ameher
depth at cen}re
Optical e thîejney ok a recver ube is
deinec
cas the rachon ok ineident sojar vadi ahion
enengy on 4a5S COYT Wweis fseTred to

heat trans her twid a s therma nergy indde the

as0rbr tube. s}ablis hes the man. limi1 toT
colleeti0 n eftice hcy
)Rlahon bl thermal Viiency P optical eklietenuy
AAoss
Therma etiuency
46

o optiead eblieieney
 Tojad heat loss

aToal heat spplied I x Ap .

in
5 Signilicance ok rekleckor temperaBure
îs that m a r e the te mpe ra-
therma anady sis
more will be the losses
4uve
u ve
electo r sun s
Comimqram
As most o the enerSy
absorbed înshe.
releeted bnt got
not
noactually
heat 4 hena reduces
ad which is not
Use

Thus owtr the rele ctor

optical e kkiciency
hdher the optica e
em
ty
tenperalure

4 ine kocusin9 sysBems (2D co ncenirators)

with a
Concentrate solar
radiation linedrly,
ngle axis irdcking Sy stem
stems C3D conantrators)
Poimt torusind sy Point
solar beams on a n g e
ConcentTale
n t c e sElHat¢s the use o
wo
rerei ver , which
syEtem.
ax1s tTacting
Parabolie trough
i n e focuing sy stems
Hellosjafs
freshal co 1ector.
co le ctors ,

Solar Thermal
rma co}lecto,
Co}lecton,
&yetems 5olar
Poimt0Cuing Linedr Freghe
unedr Fregnel
Solar Tower
Para bolic dish,
47
 2.40E-01 1000

900
2.20E-01
800

2.00E-01 700

600
1.80E-01
500

1.60E-01 400

300
1.40E-01

200
1.20E-01
100

1.00E 01 0
900 950 1000 1050 1100 1150 1200 1250 1300

Time of the day (Hrs)

 sunlight

support for cooking pot

parabolic miror
rack

48
 6 Date:- ol |o6/20214
PARABOLOID SOLAR COOKER
AIM:
To conduct heating and cooling test on a Paraboloid concentrator solar cooker, and to find optical

efficiency factor and heat loss factor.

THEORY:
Paraboloid concentrator solar cookers are concentrating devices with a dish type reflector directing
most of the intercepted solar radiation to a point focus. The cooking utensil is supported at its focal

The focal points of paraboloid solar concentrator are generally somewhat diffuse due to
point.
in the surface. Nevertheless, focal point temperatures between 150°
optical imperfections reflecting
C and 400° C can be obtained. The cooking utensil is usually supported at the focus in such a way

that a major part of the reflected radiation is incident on the bottom of the vessel, thus creating a

heating situation very similar to traditional open fire cooking. The paraboloid system require
frequent orientation towards the sun, usually every 10 to 15 minutes so that the focus of concentrated
radiation is maintained on the coking utensil. Paraboloid system collect only the beam component of

solar radiation.
The performance of the paraboloid concentrator solar cooker depends mainly on two parameters-

Optical efficiency factor (F'n.) and Heat loss factor (F'U). The optical efficiency factor defines the
theoretical upper limit of the overall efficiency of concentrator solar cooker. It relates to the
perfection of reflector surface area, its reflectance, absorptance of the outer surface of the cooking
pot ete. The heat loss from a paraboloid concentrator solar cooker primarily depend upon the pot
water temperature, wind speed, surface area of the cooking pot and orientation of the collector.

(a) Heating curve:

During the sensible heating of water, the time taken, dt for water temperature rise dTw is:

dr = CmCp)rdT (1)
Qu

(mcp),dTw (2)
atP'Apolp-AcUi(Tw-Ta
Where, 'F' ' heat exchange efficiency factor, '(mCp); is the heat capacity of both water and cooker,

'Q'is the useful heat gain by water, 'n. the optical efficiency, '7,' beam insolation on the plane of
overall heat
paraboloid, 'A,' aperture area of paraboloid concentrator, 'A' cooker surface area, 'U
loss coefficient for the cooker. If the insolation and ambient temperature are constant over a certain

interval of time 't, then Eq. (2) can be integrated over the time interval (water temperature rises

from Tw1 to Tw2).

49
T=
P (TwTa (3)
Where, 't,' is the time constant obtained from the cooling curve and C' is the concentration ratio
(Ap/Ab). Eq. (3) shows the
dependence of time t on insolation and ambient temperature. It is known
as
governing equation of the paraboloid concentrator solar cooker.
The optical
efficiency factor is obtained from
from Eq.
Eg. (3).
d
(3) and is as follows:
no
)-
1-e t
4)
Using 'F'no and 'F'U, it is possible to
cooker under any given climatic
approximately predict the sensible heating period of the
conditions (h and Ta). The time for sensible
ambient temperature up to 100° C can heating of water from
be obtained by
rewriting Eq. (3) as:
Tboil TonFU100-7a
no 6)
A plot of Tboil Vs could be referred to as the characteristic curve of the cooker.
b) Cooling curve:
Analyzing over an infinitesimal time interval during the sensible cooling of water, the time taken dt
for water
temperature fall dTw is:
dt =- mCp),dry
Q (6)
d r =--mCp),dTw
[F'AU(Tw-Ta)l
(7)
Where, 'Q is the rate of heat loss from the
pot. Assuming the 'U' and "Ta' are constant during the
cooling test, Eq. (7) can be integrated over the time interval
t
during which the water temperature
falls from Two to Tw
T=-mCp)e,

F'AU
(8)
Eq. (8) can be written as:
(Tw-Ta) = (Two-Ta)e"to

Where, 9)
= 7Cp)
TopAU
It may be
(10)
seen that the
temperature difference (Tw-7) falls to (1/e) of
time
the initial value after a
tTo. Thus To is the time constant for
=

cooling and can be found from the cooling curve. It

would be even better to find it from
semi-log plot of the variation of water temperature with time.
50
The value of 'F'U can then be found from Eq. (10).
Energy balance equation for the system can be written as:
Energy in = Energy absorbed by vessel + Energy loss

Apl=nolA, +(1-no)lA, (11)

Where, 'n' is the ratio between energy absorbed by absorber and incident solar energy, which is

known as optical efficiency.

Further application of energy balance yields:
Energy absorbed by vesse! Useful energy gain by water and vessel + Energy loss to surounding

(12)
nlAp=(mCp)w+(mCp)u+UA T, -Ta)
Hence, thermal efficiency is calculated as:

th mcp)w+(omCp)u drn -UydcT,-Ta) --== (13)

IAp IAp
The overall heat loss coefficient is defined as:

U =Up +U, +U (14)

The total heat transfer (convective + radiative) from bottom, side and top surface can be calculated

as:
Q=UhAb(T, -Ta) = [hA, (T% - Ta)]+ oA,E(T; - T) (15)
U,A,(Tsa-Ta) = [hA,(Tad -Ta)l+ oA,e(T:a-T (16)

=UA-(T -T) =
[hA,(T, -Ta)+ oAe(T* -Tsky) (17)
Where, h 8.55 + 2.56V W/m?K, Tp. Tsa and T, are the bottom, side and top surface temperature

ofthe vessel. T;' is the reflector surface temperature. Tsty' is sky temperature (Ta-) considered
in radiation heat transfer.

The value ofoverall heat loss coefficient can be substituted in Eq. (13) to get no
interval) is defined
The cooking power of solar cooker (10 minutes as:

P =(T,-Ti) mORu (18)

600

Cooking power for each time interval can be transferred to a standardized cooking power, Ps, by

multiplying the cooking power, Pi, by the standard insolation, 700 W/m (as mentioned in the ASAE
recorded during the corresponding interval.
S580) and dividing by the average insolation, li,
P, = P (19)

EXPERIMENTAL SET UP:

It consists of a paraboloid concentrator with stand and provision for orientation. A black coated
cooker is placed at the focal point of the concentrator. There are four thermocouples to measure

51
 ambient temperature, water temperature in the cooker, cooker bottom surface
temperature and
reflector surface temperature. Two additional thermocouples are used to
the outer surface
measure

temperature of the cooker. A digital weighing scale is used to measure the weight of an empty
vessel as well as water in it. Anemometer and solar flux meter used to
are measure wind velocity and
solar radiation level respectively.
SPECIFICATIONS:
1. Concentrator:

Aperture diameter : 1000 mm

Reflector material anodized aluminium sheet having reflectivity of over 80%.
No. of reflector sheet:24
Focal length 200 mnm

2. Cooker:
.
Aluminium darkened surface (3 litre capacity)
3. Digital weighing scale: 0 6
-

kg+ 0.5 gm
4. Thermo couples : 8 Nos, Cr-Al

5. Panel:

Mains switch :Rockertype, DPST with illumination, 16 A

Temperature :Digital0-999°C, 8 channel

PRECAUTIONS:
1. Properly connect the power supply.
2. Operate selector switch of temperature indicator gently.
PROCEDURE
1. Position the solar cooker set up with the required orientation.
2. Measure known amount of water (say 1 kg) and pour in the cooker.
3. Switch on the digital indicator.
4. Note down the solar radiation level
(beam radiatipon), Wind speed, Water temperature in
the cooker (Ti), Cooker bottom surface
temperature (T2, Ts and Ta), Side surface
temperatures (Ts), Top surface temperature (Ts), Reflector surface temperature (T) and
ambient temperature (T8) once in every 5-10 minutes.
5. Once the water attains highest temperature, mask the concentrator to start the cooling test.
6. Note down the water and ambient in every 5-10 minutes till the system
temperature once

attains equilibrium.

52
 7. After the test, unplug the electrical connection.
8. Various energy parameters are calculated to evaluate the performance of paraboloid cooker.

OBSERVATIONS:
- D78s4 m2
Aperture area of the concentrator, Ap
Surface area of cooking vessel, Ac -o538 m2

Cooking vessel base area, Ab O-03 46 m

Mass of water taken for the test, m 2 kg
Mass of the cooking vessel, mu 1.8 kg
= 0.20
Emissivity of vessel surface, t

(A)Heating curve:
Solar Thermocouple readings (°C)
Wind
beam Vessel bottom Vessel Vessel Reflector| Ambient|
S. Time radiation Water side
Velocity
top (T7) (Ts) V (m/s)
No. T
(Ti) (T:)|(T3)(T) (T) (T)
(W/m) 42.8 81-G o
50-3
4945L711 3S.2|74-7 62.9|44-7 G0-742
0-3
2 9:5 747 454814 73 541 74-5 GG0.2 423 o
3 756 52-3 99-1786682 82 G9.4 G1-7 45S31-9
4 100 780-3 58-7 1067/35.2 72 88 712 12-1 44-1 32.4 O
5 10:65 789.3 64-4|117-1 93-3 85:5 8-882-8 81-2 44-4 32
G10110 792 73.3 1183 93-7 89-410.86-8 87-6 4S|33.8B
7 10:15 799.8 77 121-5 947|943 103s| 88|37-8| 42-9 82-7
33:3 O
8 10:20 8316 |83.5 129.42 61 |12251 4-6q12493
4 10:25 828 88-7|1259 1313 44.5|19 96.6 93.8 41.9 93.3
3S0S91:7 i127.3 145 441 124 94 954 42.1 38 1
j:35 3442 974 138 146 l04.5 1295 - 5 S3 44-3 33.2
Paste data sheet
B) Cooling curve:
Time
S. No. Water (Ti) Ambient (T:)|

53
Sr.No Time Time (sec) Tw Td=wA In (Td)
10:35:00 L 419 31113 66.306 4.1942804
10:40:00 300 93.064 30.811 62.253 4.1312067
10:45:00|_60 88.725 30.459 58266 4.0650187
10:50:00 900
84.78630.252 54.534 3.9988244
10:55:00 1200 81.35 30.881 50469 3.9213593
11:00:00 L 1500 78.219|30.783| 47436 3.8593814
11:05:00 1800 75.223 30.526 44.697 3.7999064
11:10:00 2100 72.328 30.605 41.723 3.7310525|
9
11:15:00|L 0 69.975 30.925 39.05 3.6648429
1011:20:00 2700 67.821 31.267 36.554 3.5987906
11 11:25:00 3000
65.675 31.05 34.625 3.544576
12 11:30:00 3300 63.399 30.847 32.552 3.4828388
13 11:35:000 3600 61.472 30.674 30.798 3.4274498
14 11:40:00 3900 59.791| 30.87 28.921 3.364568
15 11:45:00 4200 58.157 31.112 27.045 3.2975021
16 11:50:00| 4500 56.602 31.142 25.46 |3.2371086
17 11:55:00 4800 55.221 30.935 24.286 3.1899001
18 12:00:00 5100 53.865 30.891 22.974 3.1343631
1 9 | 12:05:00_ 5400 52.659 30.769 21.89 3.0860299
20 12:10:00 5700 51.476 31.29 20.186 3.0049893
21 12:15:00 6000 50.447 31.239 19.208 2.9553269
22 12:20:00 |L 6300 49.596|31.352 | 18.244 2.9038363
23 12:25:00 6600 48.736 31.503 17.233 2.8468262
24 12:30:000 6900 47.837 31.326 16.511 2.8040268
12:35:00 7200 47.078 31.429 15.6499 2.750407
26 12:40:00 7500 46.395 31.315 15.088 2.7133694
27 12:45:00 7800 45.764 31439 14.325 2.6620063
28
-
12:50:00 8100 45.026 31.303 13.723 2.6190733
12:55:00 8400 44.395 31.161 13.234 2.5827893 J
30 13:00:00 8700 43.747 31.247 12.5 2.5257286
1 13:05:00 9000 43.129 30.843 12.286 2.5084604
32 13:10:00 9300 42.541 30.7 11841 2.4715681
33 13:15:00 9600 |41919 30.999 1092 2.390596
 34 13:20:00 9900 41.35 30.93 L 10.42 2343727
35 13:25:00 10200 40.91 3092 9.99 2.3015846
36 13:30:00 10500 40.66 31.68 8.98 2.1949999
37 13:35:00 10800 40.22 31.3 8.92 2.1882959
38 13:40:00 11100 39.9 31.27 8.63 2.15524455
3 9 | 13:45:00 11400 39.6 31 8.6 2.1517622
40 50:00 11700 39.24 31.24 8 2.0794415
41 13:55:00 12000 38.97 31.54 7.43 2.0055259
42 14:00:00 12300 38.43 31.19 7.24 1.9796212
43 14:05:00 12600 .46 31.31 7.151.9671124
44 14:10:00 12900 38.21 31.22 6.99 1.9444806 |
7.9 5
45 14:15:00 13200 31.34 6.611.8885837
46 14:20:00 13500 37.8 31.35 6.45 1.8640801
:25:00 13800 51 6.5 1.8718022
+8 14:30:00 14100 37.37 31.42 5.95 1.7833912
9
14:35:00 14400 37.19 31.17 6.02 1.7950873
50 | 14:40:00 14700 36.94 313 5.64 1.7298841
14:45:00 15000 36.8 5.7 1.7404662
14:50:00 15500 36.58 31.11 5.47 1.6992786
14:55:00 15600 36.32 30.7 5.62 1.7263317
4 15:00:00 15900 .16 30.9 5.26 1.660131
15:05:00 16200
36.11 30.92 5.19 1.6467337
0 15:10:00 16500 35.85 30.65 52 1.6486586
57 1515:00 16800 35.67 30.7 497 1.6034198
15:20:00 17100 35.53 30.65 4.88 1.5851452
59 15:25:00 17400 35.32 30.53 4.791.5665304
60 | 15:30:00 17700 35.22 30.3 4.92 1.5933085
61 1535:00 18000 35.05 30.4 4.651.5368672
62 15:40:00 18300 35.01 30.97 4.04 1.3962447
03 15:45:00 18600 35.02 31.07 3.95 1.3737156
64 15:50:00 18900 34.97 31.42 3.551.2669476
65 15:55:00 19200 34.93 31.44 3.49 1.2499017
66 16:00:00 19500 34.87 31.19 3.68 1.3029128
CALCULATIONS:
1. Concentration ratio, C =
Ap/Ap
2. Heat loss factor, F'U, =
mToAc W/mK

3. Optical efficieney factor, F'no= H:")

1-e to

4. Time required for boiling, Tboil tg rFUL/100-Ta

5. Thermal efficiency, nth =
mcp)w +(mCp)y dr
IAp dt

6. Overall heat loss coefficient, U =

U, +U, + U W/mK
7. Bottom loss coefficient, U,= hAp(Th-Ta)+aApe(Ti-T) W/mK
Ab(Tb-Ta)
8. Side loss coefficient, U, naVsd-Ta)l+oaAsE{Ts4-T)
=

As(Tsd-Ta)
W/m'K
9. Top loss coefficient, U, =
hA(T-Ta)+aAtE(Tsky)
At(Tt-Ta) W/m?K
10. Optical efficiency, no by referring F'U and F'no
11.
Cooking power, P =
(T, -Ti) 600

12. Standardized cooking power, P 700

=
P;)
13. Average temperature difference, Ta =
Tw-Ta
TABULATIONS:
Heat loss coefficient Heat loss Optical Time CookingStandardized| Thermal
factor efficiency| for power cooking efficiency
S Time factor boiling power
No. W/m K W/mK Sec W W %

UU,U, | F'U F'mo Tboil Pi Ps th

14:4S10.35.51 9.08 0815 12.7107

2 9:5010.26 4.1 4-44 4-51 12-7057 0.14 28 218S %| 56 S
3 9:55 |1o.29 9-814.59 9-7 12-7042 0-07385 Ssoq.3 231 T6 219.32 31.05
4 10:00 o.81 -45 9.69 24.15 12.793 017184748.7 180.25 6s.78 33.1 2|
5 1005(10.94 9.46:7130.o 12-7046|0-0 367 |889844 164 143.a9 4,8
G1O:1 10.94 10.04 9.918038 127083 o10453049.5 147-45 17% 02 44-8
71:1S 1o.38| 1017 9.99 3055 1271120-08217 4041-2 118-88 151o 19.28
8 1020 10.4 10.32q.42 8071 12.71770.0742 45454 18 4 12024 32.34
-

9 10:2510-4a 10-27992 30.612.72ao09438|g124 44 158 &81354G26

1o10:30 10.431o-43 10-130-97 12-12o-0441|103539 111+1 43. 204 14G
1 1D:9610-4510-4510.1 31 12-749011103 2452.08 118.32 92444 27.48
GRAPHS:
1. Time vs In (Ta) (cooling linear
curve regression) to get slope as To: Also get To from simple
graph.
2. Time of the day vs Thermal efticiency/ solar radiation

Time Time

RESULT: The energy parameters of paraboloid concentrating cooker are:

(1) Highest Heat loss factor, F'U, 2 7409

(2) Highest Optical efficieney factor, Fn = 0.1428

(3) Minimum Time for boiling, Tboil = 218S. 2GS = BG 42 m i n

(4) Maximum Thermal efficiency, 7th 56 5

(5) Average overall heat loss coefficient, U =80.220w/m
(6) Range of Optical efficiency, 7o 12.7%- 33.172
(7) Maximum cooking power, Pi = 231 76 W

for coolina sbtained from cso]îry

CONCLUSION: Tme constant
o r î f s tMe vJues
curve S4800S. Ambs'en} temp. restMHs
0ss Coeuents. Lesser the 4émp. o Te i\1 be tha
oanoUs
o54
QUESTIOONS:
(1) Discuss the various tracking mechanisms.
(2) Explain the different types of non-tracking solar cookers
(3) Solar cooker for night cooking'" Explain this concept.
(4) Explain the concept indoor cooking from outdoor focusing of solar radiation.
(5) What is the significance of ambient temperature in the thermal analysis?

55
GRAPH:E

56
 TIMEVS Td
300, 66.3005

8100, 24 286

5000 10000 15000 20000 25000

 TIME VS LN(Td)

Y-0.0001x 3.9227

R* U.998
5

2000 +000 6000 8000 10000 12000 14000 16000 18000 20000
TIME
 Time vs Thermal efficiency/Solar Radiation

Time

500 1000 1500 2000 2500 3000 3500

60.00 860

50.00 840

40.00 820

530.00 800

20.00 780

10.00 760

0.00 740

-solar rad iation Thermal efficiency

 SPECIMEN CALCULATION:
Trial mumber: 3

ArA
cAP/A o7854
0 0346
-2G99 42

mp)e mcp)t (m)u

ToAc Co Ac

S744-6
2.7o416 wm?K|
4800X 0-1548

(Twa-Ta)- ( Tw-Ta)
F Fu |(
-eto
300
2.7041G| 52.3-31:9454-20.3 4 800
756
22.61942 747
300/480o

f 0.0738S

- Ton
4boil -Foy 0n-Ta S-4-80o]n 7042L 4
FMo C 0-0138s22-64442
X100-31-9
756
boi550g 36s
(m)t (mlp)u d1 9744 6 52-8 45.4
dt
Ap 756 XO.1354

t31-75
57
UaU+Vs + De U . - hA,CTa)+6A£ (T-T*)
A (T-Ta
X0-20 (85s- 218s+
3SS xO 034G (82-31-9) + 5.47X1o x8.0346
0-03 4 (81-81.9)
U 9.g1517 w (mk
8.ss(cq.4-8).9)+ 5.671
U. hA sd-Ta)+6A, E CTsd-Ty) X0.20(8424- s18.S)
As (Tad -Ta) G4-4-31.9)

Us 9.S9 4$4 w m +5-67*10xo.20

(&T-7-3-9)
hAL(TE-Ta)+6A;8 (7-TSky).ss (340.7t 298.9*)
At (TE-Ta) (GT7-3).39
U 10-2896 w/m*
(mce)w 2 . 3 - 3 5 a ) 8131.8
- ( 5 =(52.3-35.2) 8131.8
Ph(T4 T) 600
n)Cakrng power
Pi 2317G W
00
741#75c-219.829w -Ps
)P P () -431-167t
21s2°c]- Heatíng
19 Avg. temp. di}jereNCL Ta Tw Ta 37 CUYVe

7-&615sc|-Cooling

Cum uWative awesuga 20.4-553°e|

4emp. derenc

40 FU= 12.7042 4 UI =29.7 F 0.4277

Fn0-07395 .17.27%

S8
 simgle Axis Trackers
Single axis drdckerso) Horizontal
with til1ed module cVexrtHcal
Horizontal single axisAcker
axis frdcker.
ANSWER: single dx is }rAker d)T$1ted sîngle
DAT Azimuth A434ude DAT
Dua Axis trackers - a)Tip-Ti}t tTalns.
molons 4 gedr
Uses
}lwid.
Active Tyaker poimt compressed qas
Usés
oW boiling
Passive Trdcker operaos ddj ust 4rdekers.
Manual Trdckinq
a Pane Fype co Ledst expeNSi Ve Ome . Cooing. pot isS
\ar cgoe:
oulside.sunlight r}lecds over îis emtire e]k
painted black
Can redch up}o 121¢ îMsuahed bod ok cdrdbaaTd,iwirdowon pas}ic, woocd
Has top
8oxsoarcooker: om insade.Haslarge glass
black
mefal. paînted în. 177°c
Redch upto4emp beam e n bottom ot
aunlight sunlight
Olef focus narron igh iemp. ok
Harabolic Solar cookee mejd 8 t d n d . feneraj es
On
si1s
Cookng Pot that
222Cto 260'C ,
Buf to makg so largoker to,
3 Soldt cooker WoTkS on sUnlignt
sBoraqe muSfbe emp loyed uohich
Osk înnyht, theTMa e Derqy roon1ng uwhensun no} aVa-
night, orédrly
Catn laer béUSed im hea c n be US-
change }6 store f.reledse dnect sunlian
Prinaple o phaae
able. is mefea b
with metHng temp. o 20e SUn is not a v a i a b l e +mats
ed. Sa yhN
tin Mesunshim e o u s 4 reledsig h e a t .
Such sstem
sysBem
fo sólidily
melted salt is allowed
c n have
207. effidh c

4 hgs Jage qufomatically 4Tacked parabo)ie rellecfor

ys injo the
standind oBsjde the kiHchen; E m refle4s sunawau.
the +opnost Anothe
kiichen fhrough ah openi nd bYO
rehlecfor guther con CAntraes rays on the
seconddry 1s painied bldek. Coun cnok
bottom o the cookînd pot. wuich
people.
sood har lange group }
5) ambient temperture or ca udhon side,
We us
So when ambtent emp.
top boto o loss CDeuends. hencu 60 higher
i} directly akteehs (UA) G (@1).
changes Teducts he heat loss f
the suroundin temp. 9o1s
thus încrease ubeu hiat gain.

59
 Cold Water Tank 2
Air vent
Over low
Valve 2 Valve 3
Pipe

Tap D
Thermometer 3 ways
Valve 8 vale

Valve 6 Valve 5
Valve Thermometer
Valve 7 4
Halogen Fixture FPC Pressure gauge
Radiation Meter Flow meterQ )
Thermometer 3
(Forcemode) Fan

Thermometer 1
|Anemometer
Pressure gauge 1
Cold Water Tank 1

Pump1 Valve
 Date:- oo612021
FLAT PLATE SOLAR WATER HEATING SYSTEM
AIM:
To evaluate:

I. Overall heat loss coefficient

2. Heat removal factor and

3. Instantaneous efficiency of flat plate solar water heating system in forced mode.

THEORY:
The flat plate collector is the heart of any solar energy collection system designed for operation in
the low or medium temperature range. It is used to absorb solar energy, convert it into heat and then
to transfer that heat to a stream of liquid or gas. It absorbs both the beam and diffiuse radiation, and is

usually planted on the top of a building or other structures. It doesn't require tracking of the sun and
requires less maintenance.
The performance of a solar water heating system depends upon different design and atmospheric

parameters. All the heat that is generated by the collector does not resulted into useful energy. Some
of the heat gets
losses to the surroundings. The amount of heat losses depends upon the convective
conductive and radiation heat loss cofficients. Estimation of heat loss coeficient of the flat plate
collector is important for its performance evaluation. A higher value of heat loss coefficient indicates
e lower heat resistance and hence the lower efficiency.
Overall heat loss coeficient is defined as the sum of loss coefficients for side and bottom surfaces
and the top glass cover. t is an important parameter since it is a measure of all the losses and is

given as:

U =U +U, +Us
(1)
Among all heat loss parameters the top loss contributes the most. The top heat loss coefficient is a
function of various parameters which includes the temperature of the absorbing plate, anmbient
temperature, wind speed, emissivity of the absorbing and the cover glass plate, tilt angle etc.
Klein's emperical equation for calculating the Top loss cocfficient is given as:

U- M o(Tp +Ta(2+Ta) 2)
2M )-M
Lo.o5M(1-Ep)+Ep C

Where,
M =Number of glass covers (1)

61
 C =365.9(1 - 0.00883 0 +0.0001298 )

(1-0.04 hw +0.0005 h(1+0.091M

w Convective coefficient between the glass cover and
surrounding air
Ep Absorber plate emissivity
&c Glass cover emissivity

The thermal losses separated as conductive,

are
convective and radiative losses. These losses
take
place from the system to surrounding from top, bottom and sides. The different losses at
different
space are pictured in terms of thermal resistances as shown in Figure 1. The various
dimensions of a
flat plate collector are shown in Figure 2.
Heat removal factor represents the ratio of the actual useful
energy gain to the useful energy
gain if
the entire collector were at the fluid inlet
temperature. depends upon the factors like inlet and
It
outlet water temperature, the ambient temperature, area of the collector etc. The importance of heat
removal factor remains with the
efficiency of the system. For a highly efficient system a higher
value of heat removal factor is must.

Ta

1 7at Ta
UtAp

UsAp
Ta W Qs TP Equivalent to 1
al
UIAp
UbAp
Qb

Ta p

Fig.1: Thermal resistance network showing collector losses

W
Tar
Qs
L2

Fig. 2: Various dimensions of a Flat plate collector

62
Fa -exp|h3 (3)
The thermal energy is lost from the collector to surroundings by conduction, conveetion and

radiation. The energy balance equation could be simplified as:

Qu=ASUA,(T> -Ta) (4)

Here 'S' is the solar radiation absorbed by the plate. The performance of a FPC is described by an

the losses in collector by means of the difference between the

energy balance equation which gives
input solar energy and useful energy available.
lost from the collector in terms
It is convenient from the point of view of analysis to express the
heat

of an overall heat loss coefficient defined by the equation:

(5)
Q =U4p(T,-Ta)
Here, 'Tp' is the absorber plate mean temperature.
The absorber plate mean temperature could also be calculated using the following Equation

Tp=T1+ FrU (1-FR) (6)

For
Eficiency is the most important factor system. This factor determines the system's output.
for a

a flat plate collector based solar water heater system

the efficiency is defined as the ratio of the
The value of efficiency is
useful energy delivered to the energy incident on the collector aperture.
dominated by parameters like product of glazing's transmittance and absorbing late's absorptance,

of global radiation falling on the collector, water inlet temperature and ambient air
intensity
temperature.
The heat loss and gain can thus be calculated, if the average plate temperature is known. However,
this temperature is generally not known. Hence the instantaneous efficiency could be redefined as:

(7)
Since the value of heat removal factor (FR), transmissivity-absorptivity product ta and overall heat

loss coefficient (U,) are essentially constant, for the given collector design and its working

plotted against (T-Ta)/I straight line with a

condition,it is seen from Eq.(7) that if 7i is a

would give the

negative slope would be obtained as shown in Figure 3. The intercept on the y-axis
value ofFaTa(4,/A)}. while the slope ofthe line would give the value of |FRU, (A,/A«)}
In Eq.(7), the value of n; is based on the collector gross area (A,). It could be based on the absorber

plate area (A) also. In that case, the term (A,/A) would drop out of Eq. (7). The intercept on the y-

axis would then be FRta and the slope of the line would be FRU. So,

a0 a1Ta) (8)
63
 a 1 AY
AX

ao

Fig. 3:H-W-Bequation
Eq(8) is widely known as H-W-B equation. Here, the value of solar radiation
(), inlet water temperature
(Ti) and ambient temperature (Ta) are constants and a0 and a1 are known as H-W-B
constants. The
Hottel-Whillier-Bliss (H-W-B) generalized performance analysis is
probably the best available
mathematical description for the performance of flat
plate
collector.

EXPERIMENTAL SET UP:

It includes the flat plate solar water heater with tank which can be operated in thermosiphon and
forced mode under simulated solar radiation. Various
sensors viz. temperature, pressure, flow rate,
solar radiation, wind velocity are used to evaluate the
performance.
SPECIFICATIONS:
Table 1: Overall
Specifications of the system
Components Specification Remarks
Water heating Collector area: 0.716 m Collector: Flat plate collector.
system (Collector Tank capacity: 50 L To collect and transfer heat
and water tank) Tank: non pressurized aluminum tank.
To store water
Halogen system Halogen fixture's area: .0.72 m2 Halogen: To supply the required
Number of halogen lamp: 21 intensity on the collector.
Power:150 W each Regulator: To adjust the intensity at
Regulator: 5000 W the desire level
Radiation meter Range: 0 to 1999 W/m2 To measure the radiation level on the
Power supply:DC collector
External water Capacity: 80 L Tosupply cold water to the heating
tanks system
Water pump Power suply: AC To lift water upto the desired level.
Power: 0.5 hp Tofacilitate forced mode operation.
Stop watoch With electronic On-Off switch To detect the time during natural flow
and a Reset button rate measurement
Fan Range:0 to 5 m/sec | To supply the wind at the desire speed
Power supply: AC with
regulators
64
Components Specification Remarks
Water flow meter Sensor: Mini turbine wheel based technology.
(for forced mode) Flow range: 0.5 to 25 LPM To measure the water flow rate during
Working voltage: 4.5 to 24 VDC the forced mode operation.
Max. Pressure: 17.5 bar
Working pressure : 0 to 10 bar
Max rated current: 8 mA
Withstand current: 15 mA
Working temp : up to 80°C
Storage temp: 25 to 65°C
Accuracy: 1%fsd
Supplyvoltage- 230 V AC.
Anemometer Air velocity: The anemometer can measure the air
Range:0.4 to45.0 m/sec velocity and the ambient air
Resolution: 0.1 m/sec temperature.
Accuracy: +2% +0.1 m/sec) The air flow sensor is a conventional
angled vane arms with low friction
Air Temperature:
Range: -14 to 60°C ball bearing.
The temperature sensor is a precision
Resolution: 0.1°C
Accuracy: 0.5°C thermistor.
Power supply:DC 4*1.5 AAA
size
Pressure Gauges Sensor: Semiconductor thin-film based
Range: 0 to 6 bar technology.
Accuracy: t3 kpa Works on the principle of generation
Output: 4 to 20 mA (+3) of electrical signal due to exertion of
Input: 4-20 mA DC pressure.
Power: 220 VAC To measure the inlet and outlet
pressure
Thermometers Sensor: Sensor is RTD based platinum probe.
Class A sensor Works on the principle of variation of
Range: -200 to 650 °C resistance with temperature.
Accuracy: +0.15 +0.002*(t) To measure the inlet, outlet, plate and
Where t is absolute value of tank water temperature
temperature in °C
Supply Voltage: 230AC

Table 2: Detailed specification of the Solar water heater system

Overall data Glazing

Overall collector dimension: 915 x 810 x 95 mm Glazing type: Toughened Glass
Weight of the collector: 13 kg Glazing thickness: 3 mm
Aperture Area: 0.63 m Glazing transmission: 85 %
Glazing Emissivity: 88 %
Absorption plate Risers& headers
Absorber material: Copper Number of risers: 6
Absorber plate thickness: 0.12 mm Riser dimension: 800 mm
65
Absorber plate dimension: 115 mm Headers dimension: 882 mm
Emissivity of surface: 0.12 Test pressure: 4 bar
Absorption of surface: 0.96 Maximum working pressure: 2.5 bar
Riser size: 10.2 mm/12.5 mmm
Insulation Insulated tank
Insulation material: Rockwool Tank type: Horizontal
Insulation density: 48 kg/m3 Tank materials: SS -304
Insulation thickness-base: 50 mm Tank insulation: PUF
Insulation thickness-side: 25 mm Tested pressure: 3 bar
Conductivity: 0.04 W/mK Tank size: 815 X400 mm
Casing Overall Efficiency
Frame type: Aluminum 80 %
Casing thickness: 1.4 mm

PRECAUTIONS:
1. During draining from the hot water tank do not open the exhaust valve in one go.
2. Do not touch the halogen fixture by your hand.

3. Do not run the pump in dry condition.

4. Do not open the tap the three way valve without

or
taking utmost care.
5. Do not touch the back side of the control panel.
6. Do not spread water over the control unit.

PROCEDURE:
1. Fill water in the cold water tank 1 and switch ON the main.

2. By operating different valves, pump the water to cold water tank 2 and switch it OFF.
3. By operating different valves, slowly fill the hot water tank completely.

4. Switeh ON the halogen lamps and adjust the intensity by referring the radiation meter.

5. Switch ON the pump and adjust the flow rate by operating pump regulator as well as gate valve.
6. Wait for steady state and then note down the water inlet (TINc), water outlet (T2Nc), Plate

(T3), Ambient (Ta) and water in storage tank (T3) temperature.

7. Calculate (71 = 0.96587INC +0.726) and (T2 =0.9685T2NC -0.0258) as both sensors

are non-calibrated.
8. Also note down, radiation level (). Wind velocity (V), water flow rate (Q). Inlet pressure

(Pr) and outlet pressure (p:).

9. By keeping the same radiation level, increase the flow rate and note down various parameters
after attaining steady state.
10. At the end, switch OFF the pump, halogen unit and main panel. Close different valves.

66
OBSERVATIONS:
) Radiation level: 554_W/m
(ii) Wind velocity: m/s
(ii) Collector tilt: 62_
Flowmeter Temperature (°C) Pressure (kPa)
reading
S.No. (lpm)
Water Water Plate Ambient Tank Inlet Outlet
inlet(T) outlet (T2) (T3) (T) (Ts) (pi) (p2)
L2 32 84% 4%9 314 817 109.4 107 8
2 33.3 3s 4 9 8 31-6 32 32 109-4 107-8
34 34.4 3S9 509 31-7 32-6 |1-6|1079
4 359 371 5 32 837 109-8|108
5 36-8 37:7 62.5 32.934:510108
98 38853.2324 858 10-6 108 6
CALCULATIONS:
1. Convective coefficient between the glass cover and air, hw 8.55+2.56 V WmK

2. Top heat loss coefficient, U= CM oT)247a) W/mK

L o . 0 5 M ( 1 - 5 p+
) + E+
p t - 1 )

3. Bottom loss coefficient, U, =F W/mK

4. Side loss coefficient, U. = atl;)lak W/m K

5. Overall heat loss coefficient, U = U, + U, + U, W/m?K

6. Heatloss from the collector, Q UA,(T,-Ta) =

W

7. Useful heat gain by the collector, Qu ApS- = W

8. Absorber plate effectiveness, 0 = tanaMd/2) Where. M= U_2

[M(W-d,)/2] kpop]
9. Flowing fluid convective coefficient, h = W/mK
10. Nusselt number:
(a) For smooth riser with constant heat flux and laminar flow, N, = 4.36

(b) For fully developed turbulent flow, N, = 0.023R,08P04 (for heating of water)

11. Collector efficiency factor, F' =

1
7W-do)d+dol Tdh2k
In(do/d;)

12. mwep
Collector heat removal factor, Fr =AU1Ap exP|hyC
67
 C
C
13.Plate temperature (Analytical),Tp Titeu1-FR)
=

14. H-W-B constants, a0 = Fata and a1 = FRU

15. Input power to the collector, Qin = I.A W

T) W
Qu mw C, (T.
-

16. Useful output power from the collector, =

17. Instantaneous efficiency, ni = Qu %

Qin

18. Instantaneous efficiency (using H-W-B constants), n = a0 -a1

19. Pumping power, P = y a W (consider , = 70%)

plp

RESULT:
S. Flow Plate Plate Overall Efficiency Heat Inst. Inst. Pumping
No. | rate temp. temp. | Heat loss| factor removal efficiency Efficiency power
lpm) (exp.)(anl.) coefficient factor (H-W-B)
12 489 46.74.0125 0-37s 0.363 429570.07 0.045s|
2 2 44-8 4123 403% o-8 7460.8G 7 41.76 .72 0-06
3.4 S0-9 4T744-6594 0.974 0.3698 52.09 G.2G0-1376
4 4 S2 4846| 4-0812 0 8736 .3649 89-15 .49 0-1714
S 6 $2-54533 4.031G 09120 0-g088 21 14 71-14 2262
G7 s3.246-o6 4-1027 o-9142 0-9119 1G-95 70.63 0-333
head daiy 1 mote than
CONCLUSIoN: Amaly+icdd usefu dcrUdd (AT)watec is not
experimental heat gaun becauSe
mcheasis wv1th power
considerd im HTS on. Pumpi
imchea sANy Hov ate
QUESTIONS: U

(1) What type of absorber plate coating is preferred? Why?

(2) How do you fix the orientation of the water heating system and slope of the collector?

(3) Define recirculation ratio.

(4) What do you mean by stagnation temperature of the collector? Write its significance.

(5) How do you select the 'Nu' correlation for riser side flow in case of thermosiphon flow ?

68
 SPECIMEN CALCULATION:
Trial umber: 2

hw 8.ss + 2.56 (o) =8.5ss wlmK|

M fs(T+T) (TT
p-Ta 1 33 + (M -M|
-05M-Ep)+Ep

962-459 (48.8-31.6 3.SS

C4484173) +0:15115
567x1 (922.3 +304.6) (302.8+804-)
+ (2t0-75175-)
0-05 (1-6.12) 40-12 O-88

U287886 w]mK

k 08 Up
0 05

(LtL)tgks (o-915+0.310)o.095 x o.04 0.3588 8 W/m25

4) U 0.915 X0-8ox0025

0-87886 +0.8+0:8S38 4.0926 w/*K|

U + U+ Us
-

7O

U A , (Tp-Ta) 4.0226 x0.63 (498-31-a) =|46-2882WJo

A p S -Q, -(0-63X554X0-85xo 36) -462382

Qu 238.S621 W

69
M-p
Mp 386X000012
4:0326_
9.8806s
tamn M(w-do) /2 tanh 9.-8s06 (o127-0-o1)
M(w-do)/l2 3.83o (o1)-00125) /2

- 0-914 62
h Nuk Re 4 m 4 X O-08813

d JTd; JXO 0102X 0-0067 |2 X

Re 968
Nu 4 36
. h 4 3 6 0-6250=267.19S3 w)n*k
O.0J02

19)Nu4-26
WUT-
w-4.)gid, * JTdh 2
I(doldi)

o-127 x4-0826 4-0826

(0-127-0-0125)0 9146 +0-0)5sXO.of02 x
267-19S3
93 X 336
(O-0125
0 0102.
F 0-87469

70
 fp D Ap
o-68012X4063-7
40326 X 0.69
exp) O.8746x4.032X0-63)
0-08312x4068-7

FO86752
11 T
To Tt t Qu/Ac (1-FR) T 9653( 5%:39) 4to.726 82-887c
FeU
32-887 4 238-5621/0-63
82-887 + (1-0-
0 86752 X4-0326
86752) =47-226s'e

14 4 feCA 0-86752 X0-8s x0-g6 0-7078g8 -d,

4 feU = 0-36762 X 4-022% =8.4-3 84-a,

1 i 554 X0-63-|349.02 W Qin

14 u w pwoTi
TTa 0-968Sx 85 -
0-0258 33.963ss°c Ta-To

O.038128 x 4068-7 (33-96855 -92-887)

u145.703 W

71
 u 145.7639
849-02 -41-76

H-W-B constants bdsed ), =4,-a, (Ti-Ta)

0-707898 - 3 . 4 9 8 4 x 2 887-31-6

564
G9-716%
3
mwAP (1og.4-107-8)xo
9P 0-033128 x

993-86X 0-70

PP 0-076 ISw

72
 ANSWER:
is prefe rred. Jn solatapplic
selective sur}au coatinq
ahon material absoob solar energy theyY aet hot
radiaion.
so he-emit part of enerdy ds the rma
Selective sI materials have high absoptamL in solar
e m i H a n L , sînce they
but low +herma
range
anqe
on 4 Cah Supress thermal
maximize solaT dbsoxpti
ve-radiaHon.

) As pet dept ok en erdy, GOv. US 4heyshoud be 0riened

geaqnaphically 4o maximize the amount ° d daiy
itis
SAAsona solar energy. for
northerm hemisphere
4S1* ahg)e 13 angle o
tTue south dpima co1lecfor oñe hda fo
it oui Too
on
your laude. While tixing i1t.
considet angle ooof o optimal

9 is ¢ekined ds the alue sk low die thed back

4o recieW aBed tank re) ative 4o +he hlow dmected
to owlet pott
1s he semp. fn s0lam sysfem i n
ay 3tdgnaHoN temp.
4ime under n o jow ondi%bng. 4} is
periods o
ud temp. în solar olle ctor în periods o
+hereone enerd y 1s }dkn jrom solar
4 m e whete
no use tddiance £ amlefent
eSWs om ven
Colleeo1 cOmsidered wYule deiwng sole
4emp. Tnis HemP 1
eysems
+ i s selechnd depOhdinq upon he hatt +hat}
s e r s euH-
o n cond ems ahHom is, happehi ng 'n
m e.Kilmwise or dnpwise.

73
 Reflector (pane
mirror)
Solar energy
erstering direc
reciy Glass sheet cover

Container with food

to be cooked
Inner metal box
(Painted black from
insxde)

Outer wooden box havinq

thermocol lining insidce

100
 10 Date:- 22/a6/2021
BOX TYPE SOLAR COOKER
AIME
Thermal testing of solar box cooker to determine of first and second figures of merit.

THEORY:
Due to the high increase in the prices of fuel and energy, the search for alternative cheaper source of

energy is of necessity. Therefore, solar energy is becoming a viable option. Solar cookers are rather
important applications in thermal solar energy conversion. The use of solar cooker for cooking
and remote
purposes is spreading widely in most developing countries and in particular in villages
areas. The solar cooker must be high quality, affordable, user friendly, light weight, stackable and a

family size. Current designs of solar cookers normally used are box cookers, concentrators, and flat

plate collector cookers.

The basic purpose of a solar box cooker is to heat things up cook food, purify water, and sterilize

instruments. A solar box cooks because the interior of the box is heated by the energ8y f the sun.

the It turns to heat energy when absorbed by the dark

Sunlight enters the solar box through glass.
absorber plate and cooking pots. This heat input causes the temperature inside of the solar box

cooker to rise until the heat loss of the cooker is equal to the solar heat gain. Temperatures sufficient
for cooking food and pasteurizing water are easily achieved.
The important parts of a hot box solar cooker include:

Outer box: Made of galvanized iron or aluminum sheet.

a)
b) Inner cooking box: Made from aluminum sheet and coated with black paint so as to easily
absorb solar radiation and transfer the heat to the cooking pots.

c) Thermal insulator: The space between the outer and inner box is packed with insulating material
such as glass wool pads to reduce heat losses from the cooker.

d) Mirror: Used in a solar cooker to increase the radiation input on the absorbing space and fixed on
the inner side of the main cover of the box. This radiation is in addition to the radiation entering the

box directly and helps to quicken the cooking process by raising the inside temperature of the cooker.

e Cooking containers: Generally made of aluminum or stainless steel. These pots are also painted
black on the outer surface so that they also absorb solar radiation directly.

Generally solar cookers are thermally rated according to () stagnation plate temperature (first figure
of merit) and (Gi) time required to bring a known amount of water nearly to the boiling point ie. heat

up condition (second figure of merit).

101
 In of flat
case
plate collectors, to find the heat loss
factor U, experimentally water is circulated
through the tubes at different temperatures and observations are recorded in steady state. In a solar
cooker, there is no control over the
temperature and the operation is transient. A quasi- steady state
is achieved when the
stagnation temperature is attended. The energy balance horizontally placed
empty solar cooker at stagnation is:

InoU(Tp-Ta) (1)

(2)
Where I is the irradiation on horizontal surface at the time stagnation temperature is reached.
The ratio of optical
efficiency (no =
Ta) to heat loss factor (U) is termed First
Figure of merit
as

(F). Second figure of merit (F2) tells about the product of the heat exchange efficiency factor (F
andoptical efficiency. For the solar cooker, a high optical
efficiency and high heat exchange
efficiency factor with low heat loss factor are desirable. Bureau of Indian
Standards (BIS) has
suggested the lower limit of Fi and F2 are 0.12 and 0.40 for the load of 8 kg/m of the aperture area.
F = mcp)w, 1 (w1-Ta2)
A(At) 1 w2-Ta2
lav (3)
Twi is water temperature around
half way between the ambient and the boiling point. "Tw2 can be
taken as the upper limit of sensible heating i.e. 90°C or 95°C. lv' is the
average irradiation between
Tw' and Tw:' during time At
The time for sensible heating from ambient temperature up to 100°C is:
boil n1-
AF2
} ********-
ltav 4)
Itav' is the average irradiation during the entire span of test.
The cooking power, P of solar cooker (10 minutes interval) is defined as:

= (T -T)mcP)u
600
(5)
Cooking power for each time interval can be transferred to a standardized
cooking power, Ps, by
multiplying the cooking power, Pi, by the standard insolation, 700 W/m* (as mentioned in the ASAE
$580) and dividing by the average insolation, li, recorded during the corresponding interval.

(6)
The average temperature difference is:

Ta T T a
(7)
The thermal efficiency of box cooker is:
2 - mcp)w+(mCp)u dT
IA dt ---====--

(8)
102
EXPERIMENTAL SET UP:
It consists of an insulated box with lid. A utensil with black coating is within the box. The

thermocouples are positioned at different points to record temperature of absorber plate, water in the
bowl and surrounding. A digital weighing scale is used to measure the weight of an empty vessel as
well as water in it.

SPECIFICATIONS:
1. Cooker:

Box Made from MS sheet with outersize (550(L) x 550(W)x 200(H))

Inner size (475(L) x 475(W) x 120(H))
Cover :Toughened glass with frame and handle
Insulation : Glass wool and plywood
2. Digital weighing scale: 0-6 kg +0.5 gm
3. Thermocouples 5 Nos, Cr-Al
4. Panel:
Mains switch Rockertype, DPST with illumination, 16 A

Temperature Digital 0-999° C, 6 channel

PRECAUTIONS:
. Operate selector switch oftemperature indicator gently.
2. Place the cooker on flat surface.
3. Close the lid tightly before starting the test

PROCEDURE:
1. Initially check all electrical connections.

2. Place the box cooker in sunlight on level surface.

3. Not down the absorber plate (Ti) and surrounding temperature (Ta) using digital indicator
once in every 10 minutes for dry test.

4. In case of wet test, known amount of water is taken in a vessel and kept in the box.

5. Not down the absorber plate, water (Th) and surrounding temperature using digital indicator

once in every 10 minutes for wet test.

6. Solar irradiation on horizontal surface is noted by a flux meter

7. Note down the reading till water temperature attains maximum value.
8. The chamber temperature (Ta) as well as bottom surface (Ts) of the cooker box may be

checked at regular interval to understand the heat transfer phenomena.

9. After the test, unplug the electrical connections and remove vessel from the box.
10. Various energy parameters are calculated to evaluate the performance of box cooker.
103
OBSERVATIONS:
Effective area
ofthe box cooker, A =
O.225 m
Mass of water taken for the test, my= kg
Mass and material
ofthe vessel, mu =
0.628 kg (Aluminium)

S. Thermocouple readings (C)Solar S. Thermocouple readings (°C) Solar

No.
Time Absorber Ambient Water radiation Time
Absorber Ambient| Water radiation
No.
plate (T) (T3) (T I(W/m) plate (T) (T) (T3)I(W/m>)
5 0 49 32.2 706 7 11:40 g5 356 83
2 8%
321 9 40 |1150 784:3 986
3 1010 6
32.2 45|110|9 2:0 g8 348 88986
4 10 20 7 32-3 So 86 1o 13:16 104 3-5|98 982
S 10' 81 33:3 65 88 1 |13-20 10539.5 99982
Eoc3S 33S 10|801 |121330105 927 00 9 19
CALCULATIONS:
1. First figure of merit, F, = 2
(1- w-Ta)
2. Second figure of merit, F2 =
"i n _1 (7w2-Ta)
1F1 lav
3. Time for sensible heating, tboil
AF2
4. Cooking power, P = (T-T) 600 W
5. Standardized cooking power, P = Pi W

6. Average temperaturedifference, Ta = Tw-T OC

7. Thermal efficieney, n = mP)w+(mCp)u dr
IA dt

GRAPHS:
1. Ta vs P; (linear regression)
2. Time of the day vs Plate temperature / solar radiation
3. Time of the day vs Water temperature / solar radiation

TABULATIONS:
S. Change in water Cooking Standardized Thermal
No. Time temperature, power, cooking power, efficiency,
Ta (C) P(W P (W) n (%)
8
2 41-8 40.47 2g.1S
12.3 41.8 88.75 27.918
4 17.7 84.833 31.04 22.362
317 84-893 18.99 2 086
86S 34-833 27.366|19.714
104
 474 22.G4 16.4 2.23

51 20.9 14.99 10-798

9 53.2 13.93 .2 7-14-8
G4 5 3-gs2 5.09
55 g7 4.92 354
12 67.3 3-5 %
G47 |4:94 |
RESULT: The energy parameters of bOx cooker are:

First figure of merit, F 67219

Second figure of merit, F2 =

3 6S T6S
Time for sensible heating, Tboilu
Highest thermal efficiency, 7 =23-1547. +45.478
Ps-O.G04Td
Standardized cooking power equation is

cooker goes Aecrct sing

O N E Thermal
efficjency of highe femPtemp-
water temp detred se3 A
reduim thermmas eFfici
thernma eFfic
r O m s d r t to end a s gurther reduig
slows down
QUESTIONS: Variaon
in the analysis of box cooker?
(1) Why figure of merits are important
(2) Why Tw2' is not referred to 100°C?

(3) Under what condition an ambient temperature must be measured using thermocouple?

(4) What is the difference between cooking power and standardized cooking power?
and disadvantages of box cooker.
(5) Write few advantages

105
GRAPHS

106
 Standardized Cooking Power vs
Temperature difference
45.00
40 00
35.00 y-0.6042x 45.478
R 0.9707
30.00

25 00
8 20.00

15.00

10.00

5.00

0.00
10 20 30 40 50 60 70
Change in water temperature (C)
 Time of the day vs Plate temperature/Solar radiation
0.11
0.105
0.1
0.095
0.09
0.085
0.08
0.075
0.07

0.065
0.06
2000 4000 6000 8000 10000 12000 14000
Time (s)
Water temperature/solar radiation

D
 SPECIMENCALCULATION:
Trial number: 2

Tpla 0S- 83.3833 = 0-07219|

I gg2

Tw-Ta
2-F (mp)w Im F Jav
AAt w aTwa- Ta
Flav
Go S-333823
o0721 x 41d S
0.07219x g 54 6 S
0.225 x (13200-3600 100 83.3833
0-o121x I 5 4 - 6

| = 0.36 5765
1X4-18
(Te (TF-T)mCe) C3-33) Goo
C00

Pi41.8W
SPs-P 41.872)40.4.763W
Tw Ta -
G-9c averade ovet 87-9se
GTa entire +ime

7. h (mcp)w + (mp )u dT
TA dt
(1x4180+ (o628x 296) 39-33) x100
123 0. 22S GOO

t 29.1544%

107
3. Thoil fmpw infi
Afa
(Twa-Ta)

the answer as there|

oil Did no et
is-Ve value im n ie.1n (-ve)
 ANSWER:
Merit invalves ratio of opticau
etficieney 4o
f i r s t fiqume ot
is îndepend
ob}ained. Second fiq. of merit
heat Joss îs consiceTes head exch-
varidb\es 2 sh ich
an} of climaíc qlass covexs
First foM ens ures
dnge e}ficiency kdetor. overad
cooker hds low
transmission 4
nave qood optcd value means good value o
t a n s t e r coet.
Hign fa
heat
Ratt of variafjon o} waker 4emperure approdches
4here
zero dS Wafev tempe rature approdches jo0C,
1S qrea uneertainity in deciding 4he texminaHon

point of 4he time in}erva t

4 C0oking power 1s a rale of usetus energy avai lab-
e durimq heain pémod. we don+ comsiderssojar
radiaian in c0okjng pawer caUcuWahon. Jn s}and-
each imierya îs corrected
d'tdize cookinq power
4O a standard insolafi0n o 70owIn
5Advantages:
Maintaün beter alr quai4y îndoons.
redue cdrbom momoxide e missîon.

Eco-riendly.
Disddvdntages weadth er
Ca't be Used in colt cloudyf radmy
much ef¥icient in reaininq heat.
Are nat

3. Under ex nenme)y cod conditions under the candi-

Mon where usiny thermometer 1s not possible o r
desirable we use RTDe 4 thermoouples +0 measune
ambiet Aempeatuhe.
Ambied is surraunedings108 omething so pa kept
mvacwm utnmace 1ika Audoclawe W t use themo
meer so w e Use herMO LO uples 4hee