Performance Test on Solar Cooker With Augmentative Reflectors

7/31/2019 Performance Test on Solar Cooker With Augmentative Reflectors

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Performance test on solar cooker wi th augmentative reflectors

By Belay Aga MSc 00278/ 2003 December, 2011 Page 1

FFFAFACULTY OF ENGINEERING AND TECHNOLOGY

DEPARTMENT OF MECHANICAL ENGINEERING

MSC.IN SUSTAINABLE ENERGY ENGINEERING

LABORATORY REPORT ON SOLAR BOX COOKER

SUBMITTED TO: Dr.A.VENKATA RAMAYA

AND ATO BALEWGIZE AMARE

BY: BELAY AGA

ID No: Msc.00278/2003 DATE: 12/12/2011


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Experiment 4 performance test on solar cooker with augmentative

reflectors

Experimental setup

H=0.495m

L=0.495m

Where DMM is the digital multimetre to measure the mv reading of the thermocouple in the

can and DT is the digital thermometer to measure the chamber temperature

Collector area

Chamber

Can with

waterDT

DMM


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Objectives of the experimentTo test the efficiency of the box solar cooker

To predict the temperature of water in the can with time

To predict the temperature of the chamber with time

Materials used for the experimentAluiminium can

Thermocouple

Digital thermometer

Infrared thermometer

Black body

1.5 litres of water

Parameters to be measuredChamber temperature

Water trmperature

Solar insolation

Mass flowrate of air

Cooking power of the solar cooker

Theory

Introduction

The use of solar energy to cook food presents a viable alternative to the use of fuelwood,

kerosene, and other fuels traditionally used in developing countries for the purpose of

preparing food. While certainly, solar cookers cannot entirely halt the use of combustible fuels

for food preparation, it can be shown that properly applied, solar cooking can be used as an

effective mitigation tool with regards to global climate change, deforestation, and economic

debasement of the worlds poorest people.

Types of solar cookers

A survey of solar cookers worldwide shows that a wide variety of cookers have been designed.

However, the available designs of solar cooker fall into four main categories namely, the solar

box cookers or popularly known as solar ovens, panel cookers, collector cookers and

concentrating or reflector cookers. The feature common to each design is the shiny reflective

surface that directs the suns rays onto the cooking area and dark inner walls of the cooking


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area and cooking vessel. Each type of solar cooker has advantages when compared on their

cooking ability, ease of construction, and safety of use.

The solar box cooker or solar oven is the most common type of solar cooker made for personal

use. It consists largely of a box made of insulating material with one face of the box fit ted with a

transparent medium, such as glass or plastic.

The panel cooker is quite similar in operation to the solar box cooker. The same principles are

employed but instead of an insulated box only, the panel cooker typically relies on large (often

multi-faceted) reflective panels, which focus the sunlight on a cooking vessel. The collector

cooker is made up of two parts that often share a single casing: a collector for gathering heat

and a cooking part for exploiting the yield. A typical collector cooker would consist of a flat

plate solar collector, side and head mirrors, and the cooker part. The user is not affected by

radiation and heat as the cooking part is separate and protected from radiation. Oil is used as

the heat transfer medium in order to allow higher temperatures to be reached. Theconcentrating solar cooker or reflector cooker utilizes the principles of concentrating optics. It

concentrates direct solar radiation on the bottom of the cooking pot, heating the pot in a

fashion similar to a traditional electric or gas powered stove.

Calibration of the thermocouple

Table 1.calibration data for thermocouple

voltage(mv) T(oC)

0.5 400.8 45

1 50

1.2 55

1.4 60

1.7 65

2.1 70

2.4 75

2.6 80

2.8 85


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Figure 1 J-type thermocouple calibration

Sample calculations

Area of the collector

0.495*0.495=0.245025m2

Cookers shall have 7,000 grams potable water per square meter from standard testing

=7kg/m2=7litre

7lit=1m2

Xlit=0.245m2

X=.

=1.715lit

Mass of water taken to be tested =1.5kg=1.5litre

Solar insolation calculation

T = 18.90*(mv) + 31.30R = 0.992

010

20

30

40

50

60

70

80

90

0 0.5 1 1.5 2 2.5 3

Temperatureindegreecelcius

mv reading

Temperature vs mv reading for the J type

thermocouple

T(deg.C)

Linear (T(deg.C))


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Radiat ion component (Grad)

Boltzmann constant () =5.67*(10-8) w/m2. k4,=1(for black body)

G radiation= (Ts4-Tsky4) where Ts and Tsky are in Kelvin

Table 2.data for the radiation components of insolation

Tsur(k) Tsky(K) Grad(w/ m2)

343.725 290.5644 387.2977833

344.85 291.1408 394.4943069

343.875 288.9815 397.4156314

341.025 295.4753 334.6976664

346.275 295.7651 381.3256008

343.125 301.5795 316.9269647

345.375 292.1503 393.709034353.025 291.5733 470.8514043

352.425 293.5944 453.3982464

348.15 292.872 415.8547253

348.825 292.4389 424.7960172

353.925 293.1609 470.8675418

354.525 291.5733 485.9146195

355.5 290.4204 502.2516626

354.9 289.7007 500.1370566

351.75 291.4291 459.007763

351.225 294.0281 439.0510212

345.975 294.1727 387.7727212

347.925 292.1503 417.8004718

345.825 291.5733 401.1753476

343.35 294.0281 364.231161

Average 419

Convection component (Gconv)

From Heat transfer_A practical Approach_Yunus A.Cengel , for natural convection

Rayleigh number (Ral) =()()^

^*pr

Where the

g = gravitational acceleration, m/ s2


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=Coefficient of volume expansion, 1/K (= 1/T for ideal gases)

Ts = temperature of the surface, C

Tamb= temperature of the fluid sufficiently far from the surface, C

Lc= characteristic length of the geometry, m

= kinematic viscosity of the fluid, m2/s

Pr =prandtl number

The air properties are taken at the fluid temperature (average of the ambient and surface

temperature)

Tf=(Ts+Tamb)/2

Table 3. Temperature reading of chamber and water

Tsurf

(oC)

Tchamber

(oC)

T water(mv) Twater

(oC)

Tamb

(oC)

94.1 59.7 0.3 36.97 29.6

95.6 63.2 0.4 38.86 30

94.3 62.7 0.5 40.75 28.5

90.5 63.1 0.6 42.64 33

97.5 66.6 0.65 43.585 33.2

93.3 69 0.7 44.53 37.2

96.3 70.4 0.8 46.42 30.7

106.5 71.3 0.9 48.31 30.3

105.7 72.2 1 50.2 31.7

100 72.4 1.15 53.035 31.2

100.9 72.8 1.2 53.98 30.9

107.7 73.3 1.3 55.87 31.4

108.5 73.5 1.35 56.815 30.3

109.8 72.4 1.45 58.705 29.5

109 72.9 1.5 59.65 29

104.8 80 1.55 60.595 30.2104.1 81.2 1.6 61.54 32

97.1 80.7 1.65 62.485 32.1

99.7 80.2 1.7 63.43 30.7

96.9 78.7 1.9 67.21 30.3

93.6 81.3 1.95 68.155 32

Twater=18.90*(mv) +31.30 from the calibration of the thermocouple


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Figure 2 temperature profiles for the chamber and water with time from 11:40am to 3:00pm

Lc=As/P where As is surface area,P is perimeter of the plate

The plate is 8cm*8cm

As=0.08*0.08=6.4*10-3m2, P=4*0.08m=0.32m,

Lc= (6.4* 10-3m2)/ (0.32m) =0.02m.

g=9.81m/s2

For the Horizontal plate, (Upper surface of a hot plate or lower surface of a cold plate)

For RaL=104107 =1.45*104 Nu=0.54RaL

0.25=0.54*(15400)0.25=5.92

Nu=

=5.92=

.

., h=8.23w/m2.k

0

10

20

30

40

50

60

70

80

90

0 5 10 15 20 25

Temperature(degreecelcius)

time of the day from 11:40am to 3:00pm respectively

Chamber temperature and water

temperature

T chamber

Twater


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Table 4. Convective component of the solar insolation with the respective time

Taver

age(oC)

Kg/m3

(N.s/m2)

(m2

/ s)

(1/K)

pr

(w/ m.k)

Ra Nu h

(w/k.m2)

Gconv(w

/ m2)

Gtotal(w

/ m2)

50.08

75

0.88

9

1.97E

-05

2.22E

-05

0.003

1

0.7

13

0.027

8

1.45E

+04

5.92E

+00

8.23E

+00

337.3475

689

724.6453

522

50.85

0.88

7

1.97E

-05

2.22E

-05

0.003

09

0.7

13

0.027

9

1.46E

+04

5.94E

+00

8.28E

+00

345.3969

386

739.8912

455

49.61

25

0.89 1.97E

-05

2.21E

-05

0.003

1

0.7

13

0.027

8

1.49E

+04

5.97E

+00

8.30E

+00

350.4572

733

747.8729

047

50.43

75

0.88

8

1.97E

-05

2.22E

-05

0.003

1

0.7

13

0.027

8

1.23E

+04

5.69E

+00

7.90E

+00

275.6304

885

610.3281

548

53.16

25

0.88

1

1.98E

-05

2.25E

-05

0.003

07

0.7

13

0.028 1.36E

+04

5.83E

+00

8.16E

+00

325.8217

227

707.1473

23553.58

75

0.87

9

1.98E

-05

2.25E

-05

0.003

07

0.7

13

0.028

1

1.11E

+04

5.54E

+00

7.79E

+00

255.2154

882

572.1424

53

51.46

25

0.88

5

1.97E

-05

2.23E

-05

0.003

09

0.7

13

0.027

9

1.45E

+04

5.92E

+00

8.26E

+00

343.1984

297

736.9074

637

55.08

75

0.87

5

1.99E

-05

2.27E

-05

0.003

05

0.7

13

0.028

2

1.64E

+04

6.11E

+00

8.61E

+00

426.8800

466

897.7314

509

55.48

75

0.87

4

1.99E

-05

2.28E

-05

0.003

05

0.7

13

0.028

2

1.57E

+04

6.04E

+00

8.52E

+00

405.2309

78

858.6292

244

53.1

0.88

1

1.98E

-05

2.25E

-05

0.003

07

0.7

13

0.028 1.49E

+04

5.97E

+00

8.35E

+00

365.8192

185

781.6739

438

53.2875

0.88 1.98E-05

2.25E-05

0.00307

0.713

0.028 1.52E+04

6.00E+00

8.39E+00

375.8129615

800.6089787

56.08

75

0.87

3

2.00E

-05

2.29E

-05

0.003

04

0.7

13

0.028

2

1.60E

+04

6.07E

+00

8.56E

+00

422.8335

207

893.7010

625

55.83

75

0.87

3

2.00E

-05

2.29E

-05

0.003

04

0.7

13

0.028

2

1.66E

+04

6.13E

+00

8.64E

+00

441.1090

749

927.0236

944

55.92

5

0.87

3

2.00E

-05

2.29E

-05

0.003

04

0.7

13

0.028

2

1.71E

+04

6.18E

+00

8.71E

+00

460.3538

325

962.6054

95

55.37

5

0.87

5

1.99E

-05

2.27E

-05

0.003

05

0.7

13

0.028

2

1.74E

+04

6.20E

+00

8.75E

+00

461.3234

504

961.4605

07

54.4

0.87

7

1.99E

-05

2.27E

-05

0.003

06

0.7

13

0.028

1

1.61E

+04

6.08E

+00

8.55E

+00

413.6114

304

872.6191

93455.03

75

0.87

6

1.99E

-05

2.27E

-05

0.003

05

0.7

13

0.028

1

1.52E

+04

6.00E

+00

8.43E

+00

388.3867

181

827.4377

393

52.46

25

0.88

3

1.98E

-05

2.24E

-05

0.003

08

0.7

13

0.028 1.40E

+04

5.87E

+00

8.22E

+00

334.6537

752

722.4264

964

52.73

75

0.88

2

1.98E

-05

2.24E

-05

0.003

07

0.7

13

0.028 1.50E

+04

5.98E

+00

8.37E

+00

368.9016

681

786.7021

4

51.48 0.88 1.98E 2.24E 0.003 0.7 0.027 1.46E 5.94E 8.29E 351.1121 752.2875


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75 5 -05 -05 09 13 9 +04 +00 +00 818 295

51.1

0.88

6

1.97E

-05

2.22E

-05

0.003

06

0.7

13

0.027

9

1.32E

+04

5.79E

+00

8.08E

+00

308.6195

308

672.8506

918

Average

788.4139

545


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Figure 3 solar insolation with time of the day

Gconv average =369.415w/ m2

= +=369.415+419=788.415w/m2

=0.245m2

Input power

=*=0.245*788.415=193.162watt

Output power

= ( )

Where =4186J/kg.K

0

200

400

600

800

1000

1200

0 5 10 15 20 25

solarinsolation(w/m2)

time inhrs from 11:40am to 3:00pm respectively with 10 minutes interval

Gtotal(w/m2)

Gtotal(w/m2)


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=3:00pm-11:40am=3:20h=3.33hour

=.

(..)

.=16.33watt

Efficiency ( ) =

100% =.

..*100%=8.454%

Cooking power for the 10minute interval

=( )

=.(..)

=19.78watt

=

=.

.=19.10617watt

=-=39.97-29.6=7.37oC

Table 5. Instant cooking power and standard cooking power relations

P (watt) Pi(watt) Twater(oC) Tamb(oC) Td(oC) Gtotal(w/m2)

19.10617 19.77885 36.97 29.6 7.37 724.6453522

18.71247 19.77885 38.86 30 8.86 739.8912455

18.51276 19.77885 40.75 28.5 12.25 747.8729047

11.34242 9.889425 42.64 33 9.64 610.3281548

9.78947 9.889425 43.585 33.2 10.385 707.1473235

24.19886 19.77885 44.53 37.2 7.33 572.14245318.78824 19.77885 46.42 30.7 15.72 736.9074637

15.42242 19.77885 48.31 30.3 18.01 897.7314509

24.18715 29.66827 50.2 31.7 18.5 858.6292244

8.856119 9.889425 53.035 31.2 21.835 781.6739438

17.29333 19.77885 53.98 30.9 23.08 800.6089787

7.745988 9.889425 55.87 31.4 24.47 893.7010625

14.9351 19.77885 56.815 30.3 26.515 927.0236944

7.191521 9.889425 58.705 29.5 29.205 962.605495

7.200085 9.889425 59.65 29 30.65 961.460507

7.933125 9.889425 60.595 30.2 30.395 872.6191934

8.366306 9.889425 61.54 32 29.54 827.4377393

9.582425 9.889425 62.485 32.1 30.385 722.4264964

35.19806 39.5577 63.43 30.7 32.73 786.70214

9.202063 9.889425 67.21 30.3 36.91 752.2875295


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Arranging the temperature difference and the standardized cooking power, the following plot is attained

Figure 2 standardized cooking power with respect to the temperature difference

Ps = -0.230* Td + 19.55

R = 0.087

0

5

10

15

20

25

30

35

40

0 5 10 15 20 25 30 35 40

standardcookingpower(watt)

Temperature difference (degree celcius)

Ps vs Td

Ps

Linear (Ps


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Conclusion

From the table above the temperature rise of the chamber has rapid response than that of the

water temperature as expected .the water temperature increases smoothly and that of the

chamber oscillates in increasing and decreasing. The plot of the standardized cooking power

with respect to the temperature difference is not like that of the standard tool because of thelow number of data and less change of water temperature.in an interval of 2.33hrs,the water

temperature rises by 31.185oC by the average solar insolation of 788.415w/ m2 by the collector

area of 0.245m2. By this data the efficiency of the solar box cooker is 8.454 %

Documents

Performance Test on Solar Cooker With Augmentative Reflectors