I: Objectives

II: TheoryRefrigeration is the process of removing heat from an enclosed space or from a substance for the purpose of lowering the temperature. In the industrialized nations and affluent regions in the developing world, refrigeration is chiefly used to store foodstuffs at low temperatures, thus inhibiting the destructive action of bacteria, yeast, and mold. Many perishable products can be frozen, permitting them to be kept for months and even years with little loss in nutrition or flavour or change in appearance. Air-conditioning, the use of refrigeration for comfort cooling, has also become widespread in more developed nations.In method and cycle used in refrigeration, one of the most widely used for air-conditioning of large public buildings used in domestic and commercial refrigerators is the standard vapor-compression cycle. It is one of the many refrigeration cycles available for use.III: Apparatus:a. mini ice plant test rigb. KW- H meterc. Stop watch or timerd. Lo- side pressure gaugee. Hi- side pressure gauge

IV: Procedures:V: Documentations:VI: Data Gathered:Total Quantity of Water19.25 liters

Initial Temperature of Water32 OC

Final Temperature of Water4 OC

Time elapsed1 hr. 31 min. 15 sec (91.25)

Total Quantity of Water19.25 liters

Specific Heat of Water4.187 kJ/kg K

Initial Temperature of Water32 OC

Final Temperature of Water4 OC

Time elapsed1 hr. 31 min. 15 sec (91.25)

Mass Flow Rate3.51598 x 10-3 kg/s

Refrigerating Effect of Brine412.1996 W

Compressor Work0.5 KW-hr

Reading in W328.77 W

Elapsed time,Power, kWhTemp. of WaterPressure, psigTemperature, C

SuctionDischargeCompressorCondenserExpansionEvaporator

05.832261404338927

6.335.8313115365391027

8.025.8304015569391127

9.475.8294215571391127

10.355.8284215572391127

10.835.8274215573391127

11.255.8264315574391127

11.735.8254315574391127

12.085.9244315574391127

12.525.9184315575391127

16.55.9174315579391027

16.725.9164315280391027

19.125.9154315081401127

20.925.9144315982411126

22.375.9134115283391026

25.236.0124115084391025

26.236.011401508439925

28.176.010401498439924

30.156.09401488538923

39.76.1836145843871

48.376.1733135773671

60.376.263213677364-1

62.426.253113877364-1

91.256.343113876364-1

VIII: Tables and ChartsVII: Experimental Data:1. Refrigerating effectR.E= (MB x CpB x TB) + (MA x CpB x TA) + Q Transmission load+ Q Air Infiltration + F.SWhere:MB= Mass of brineCpB= Specific heat of brine, 3.82 TB= Temperature difference from the initial temperature to final temperature of the brine.MA= Mass of AirCpA= Specific heat of air, 1.0062 TB= Temperature difference from the initial temperature to final temperature of the air.F.S= Factor of Safety is equal to 10 % of the totality of product, transmission load and air infiltration1.1 Mass of BrineBrine Quantity = Volume water + Volume saltGetting the equivalent Liters of salt, we used ratio and proportion

Brine Quantity = 13.5 li of water + 3.05 li of salt = 16.55 li of brine solution1.2 Mass of AirMass of air= density of air x volumeWhere:Density of air= 1.31228 kg per cubic meterVolume of the brine tank= (0.350m x 0.225m x 0.102m) = 0.0080325 M3Mass of air= 1.31228 x 0.0080325 M3 = 0.01054 Kg Note: The initial and final temperature of brine and air, the transmission load and air infiltration values were computed and can be seen on Table 7.9 Total Cooling Load.Therefore,R.E= [16.55kg. x 3.82 x (299 K- 269 K)] + [0.01054kg. x 1.0062x (304 K-296 K)] + (0.0409024 + 0.0459145) Transmission Load + (0.0016559 Air infiltration + 0.10{[16.55kg. x 3.82 x (299 K- 269 K)] + [0.01054kg. x 1.0062x (304 K-296K)] + (0.0409024 + 0.0459145) Transmission Load + (0.0016559 Air infiltration}Refrigerating Effect= 2086.4836 KJ2. Work of Compressor

`Wc= final energy meter- initial energy meter= 5.0 kWhr- 4.88 kWhr=0.12 kWhr x 50 mins/ 60 minsReading in kWhr= 0.1 kWhr x 3600 KJ= 360 KJ3. Actual C.O.PThe Actual C.O.P. is based on actual Refrigeration effect and actual energy supplied to the compressor both measured experimentally.Actual C.O.P= Actual C.O.P= Actual C.O.P= 5.79584. Theoretical C.O.PThe suction and discharge pressure is recorded for every changed of temperature of brine. And in order to obtain the theoretical C.O.P, the first thing that must be done is to get the h1, h2, h3 and h4 of the suction and discharge pressure per intervals. The h1 is the enthalpy of suction pressure in saturated vapour. The h1 is obtained through interpolation using the pressure the Table of Properties of Saturated Liquid and Vapor of R134a, h2 is the enthalpy of the discharge pressure in superheated vapor and is obtained using the pressure-enthalpy chart of R134a. Lastly, h3 and h4 are equal to the enthalpy of discharge pressure at saturated liquid. The Theoretical C.O.P. is the C.O.P. calculated on the basis of Refrigerating effect and compressor work obtained from P-H (pressure -enthalpy) diagram. The theoretical C.O.P is equal to the difference of enthalpy h1 and h4 divided by the difference of enthalpy h2 and h1. Since there are so many intervals, the theoretical C.O.P per intervals is divided to the numbers of intervals to get the averaged theoretical C.O.P.

Figure 7.1 The standard vapour compression cycle on P- H Diagram

Table 7.1 Theoretical C.O.PNoPresure, MPAEnthalphy, KJ/ KgRefrigerating Effect, KJ/ KgWork of Compressor, KJ/ KgTheoretical C.O.P

SDh1h2h3h4

11650.296398.41430200.39200.39198.0231.596.2683

21670.296398.79431200.39200.39198.4032.216.1594

31690.303399.14433201.32201.32197.8233.865.8422

41690.303399.14433201.32201.32197.8233.865.8422

51690.303399.14433201.32201.32197.8233.865.8422

61690.303399.14433201.32201.32197.8233.865.8422

71690.303399.14433201.32201.32197.8233.865.8422

81700.331399.14433204.62204.62194.5233.865.7449

91700.338400.9433205.44205.44195.4632.16.0892

101750.338400.9438205.44205.44195.4637.15.2685

111690.338400.9438205.44205.44195.4637.15.2685

121690.310399.49433202.12202.12197.3733.515.8899

131690.290398.01430199.64199.64198.3731.996.2011

141680.290398.41430199.64199.64198.7731.596.2923

151650.283398.01430198.73198.73199.2831.996.2295

161620.276397.6431197.82197.82199.7833.45.9815

171580.262403.67425195.93195.93207.7421.339.7395

181560.248396.39432193.97193.97202.4235.615.6843

191500.234395.07431191.95191.95203.1235.935.6533

201480.221394.11429189.96189.96204.1534.895.8512

211450.214387.76428188.87188.87198.8940.244.9427

221420.207393.14427187.73187.73205.4133.866.0663

231390.193392.06440185.40185.40206.6647.944.3108

Average199.494734.1539135.9500986

5. Compressor Work vs. Brine TemperatureThe suction and discharge pressure is recorded for every changed of the temperature of brine. The h1 is the enthalpy of the suction pressure in saturated vapor while the h2 is the enthalpy of the discharge pressure in superheated vapor. The h1 is achieved through interpolation using the Table of Properties of Saturated Liquid and Vapor of R134a while h2 is achieved using the pressure- enthalpy chart of R134a. The change in enthalpy is the difference between h2 and h1.Table 7.2 The change in enthalpyBRINE TEMPERATURE, oC PRESSUREENTHALPHY, KJ/ KgCHANGE IN ENTHALPY , KJ/ Kg

PSIMPA

SUCTIONDISCHARGESUCTIONDISCHARGEh1h2

26431651650.296398.4143031.59

25431671670.296398.7943132.21

24441691690.303399.1443333.86

23441691690.303399.1443333.86

22441691690.303399.1443333.86

21441691690.303399.1443333.86

20441691690.303399.1443333.86

19481701700.331399.1443333.86

15491701700.338400.943332.10

12491751750.338400.943837.10

11491691690.338400.943837.10

12451691690.310399.4943333.51

11421691690.290398.0143031.99

5421681680.290398.4143031.59

4411651650.283398.0143031.99

3401621620.276397.643133.40

2381581580.262403.6742521.33

1361561560.248396.3943235.61

0341501500.234395.0743135.93

-1321481480.221394.1142934.89

-2311451450.214387.7642840.24

-3301421420.207393.1442733.86

-4281391390.193392.0644033.53

Figure 7.2: The graph shows the relationship between work of compressor and brine temperature. As the brine temperature decreases the work of compressor varies.

6. Refrigerant Temperature vs. Brine TemperatureThe suction temperature of refrigerant is the temperature corresponding to the suction pressure at saturated state while the discharge temperature of refrigerant is the temperature corresponding to the discharge pressure at superheated state. The time is recorded after every change of brine temperature.Table 7.3: Temperature Difference between R134a and Brine Brine temperature, CRefrigerant Temperature (R-134a), CTime elapsed, mins.Temperature Difference between R134a and Brine, C

SuctionDischarge

26-0.3245440.0026.3245

250.324454.3524.676

240.9304456.5223.0696

230.9304458.7022.0696

220.93044510.8721.0696

210.93044513.0420.0696

200.93044515.2219.0696

193.35564517.3915.6444

153.96194519.5711.0381

123.96194621.748.0381

113.96194623.917.0381

121.53674526.0910.4633

11-1.02154528.2612.0215

5-0.32454530.435.3245

4-1.02154432.615.0215

3-1.71864434.784.7186

28.86844336.96-6.8684

1-3.80964239.134.8096

0-6.04234341.306.0423

-1-7.65564043.486.6556

-2-18.06713945.6516.0671

-3-9.26883947.836.2688

-4-11.02843250.007.0284

Average11.98521739

Total275.66

Figure 7.3 The graph shows the relationship between suction temperature of R134a and Brine Temperature with respect to time.

7. Cooling Load vs. Brine TemperatureHeat Load Calculation1. Transmission LoadFor brine level:Q= U x A x tWhere:Q= Heat gain, WU= Overall heat transfer coefficient, W/ M2 KA= Area inside the brine tank (brine level)t= Change in temperature of ambient temperature and brine temperature

For Air Inside the tank:Q= U x A x tWhere:Q= Heat gain, WU= Overall heat transfer coefficient, W/ M2 KA= Area inside the brine tank (air space)t= Change in temperature of ambient temperature and air temperature

The wall composition is shown in figure 7.3. The ambient temperature and brine temperature are attained by the use of a digital thermometer and the air temperature inside the tank is assumed.Figure 7.4 Wall composition in brine tank side

1.1 Overall Heat Transfer Coefficient, U

Table 7.5: Properties of the Material

MaterialsThicknessThermal Conductivity

Steel1.2 mm13.8 W/ m.K

Poly urethaneside= 97.6 mm.0.023 W/ m.K

bottom= 65.6 mm.

Table 7.3 Shows the properties of the material used as a wall composition of the brine tank.Air film coefficientAir film outside the brine tank, ho= 22.7 W/ m2KAir film inside the brine tank, hi= 8.29 W/ m2KBrine film coefficient, hb= 600 W/ m2K1.1.1 Heat Transfer Coefficient, U (Brine level)

1.1.2 Heat Transfer Coefficient, U (Air inside)

Where:R = resistanceXs = thickness of steel Xps = thickness of polyurethane (sides)Xpb = thickness of polyurethane (bottom)Ks = thermal conductivity of steelKp = thermal conductivity of polyurethane Therefore,For brine level

For air inside

1.2 Area, M2

Table 7.6 Dimensions of Brine Tank

Size of Brine Tank (inside)350 x 225 x 312 mm

Brine level210 mm

Depth of air space inside the tank102 mm

For brine level:Area sides= (2) (0.210m x 0.350m) + (2) (0.210m x 0.225m) = 0.2415 M2Area bottom= (0.225m) (0.350m) = 0.07875 M2

For air inside the tank:Area sides= (2) (0.102m x 0.350m) + (2) (0.102m x 0.225m) = 0.1173 M2Area top= (0.225m) (0.350m) = 0.07875 M2

1.3 Temperature

The temperatures are attained by the used of digital thermometer with two probes. The first probe is immersed on the brine solution while the second probe is on the air space inside the tank though the readings on the air space starts at 26 0C up to 11 0C. Thus, the temperature from where the readings of the temperature of air stopped till -40C was assumed.Ambient temperature= 320CInitial Brine temperature= 260CFinal Brine temperature= -40CInitial Air Temperature= 310CFinal Air Temperature= 230C

2. Air Infiltration2.1 Sensible HeatQs= 1.1 x CFM x tWhere:Qs= sensible heat loss from infiltration, WCFM= air infiltration flow rate, ft3/ min.t= temperature difference between outside and inside air of the brine tank

Solving for CFM:CFM= ACH x V/ 60Where:ACH=air change per hourV= volume of the brine tank

The brine tank is considered as a tight construction and it is estimated that the cover has been removed for 7 times.ACH= 0.5 x 7= 3.5V= (0.350m x 0.225m x 0.102m) = 0.0080325 M3 0.28357 ft3Therefore,CFM= 3.5 x 0.28357 ft3/ 60= 0.016542 ft3/ min.

Note: The latent heat loss is not included in the calculation of cooling load since there are no reliable values of the inside and outside air humidity ratio.

The total cooling load is equal to the sum of the transmission load in the brine level, transmission load in the air space and the air infiltration.Table 7.7 Cooling Load of Brine LevelBrine Temperature, CAmbient Temperature, CBrine LevelQ Transmission Load, W

AreaU

SidesBottomSidesBottom

26320.24150.07880.23310.34510.5008

25320.24150.07880.23310.34510.5843

24320.24150.07880.23310.34510.6678

23320.24150.07880.23310.34510.7513

22320.24150.07880.23310.34510.8347

21320.24150.07880.23310.34510.9182

20320.24150.07880.23310.34511.0017

19320.24150.07880.23310.34511.0852

15320.24150.07880.23310.34511.4191

12320.24150.07880.23310.34511.6695

11320.24150.07880.23310.34511.7530

12320.24150.07880.23310.34511.6695

11320.24150.07880.23310.34511.7530

5320.24150.07880.23310.34512.2538

4320.24150.07880.23310.34512.3373

3320.24150.07880.23310.34512.4208

2320.24150.07880.23310.34512.5042

1320.24150.07880.23310.34512.5877

0320.24150.07880.23310.34512.6712

-1320.24150.07880.23310.34512.7547

-2320.24150.07880.23310.34512.8381

-3320.24150.07880.23310.34512.9216

-4320.24150.07880.23310.34513.0051

Total40.9024

Average1.7784

Table 7.8 Cooling Load for Air space inside the tank

Air Space Inside Temperature, CAmbient Temperature, CAir Space Inside the TankQ Transmission Load, W

AreaU

SidesTopSidesTop

31320.11730.078750.22686.06920.5046

31320.11730.078750.22686.06920.5046

31320.11730.078750.22686.06920.5046

31320.11730.078750.22686.06920.5046

31320.11730.078750.22686.06920.5046

30320.11730.078750.22686.06921.0091

30320.11730.078750.22686.06921.0091

30320.11730.078750.22686.06921.0091

30320.11730.078750.22686.06921.0091

29320.11730.078750.22686.06921.5137

29320.11730.078750.22686.06921.5137

29320.11730.078750.22686.06921.5137

29320.11730.078750.22686.06921.5137

27320.11730.078750.22686.06922.5228

27320.11730.078750.22686.06922.5228

27320.11730.078750.22686.06922.5228

26320.11730.078750.22686.06923.0273

26320.11730.078750.22686.06923.0273

25320.11730.078750.22686.06923.5319

25320.11730.078750.22686.06923.5319

24320.11730.078750.22686.06924.0364

24320.11730.078750.22686.06924.0364

23320.11730.078750.22686.06924.5410

Total45.9145

Average1.9963

Table 7.9 Total Cooling Load

Brine Temp., CAir Space Inside Temp., CAmbient Temp., CBrine level Q Transmission Load, WAir space inside Q Transmission Load, WQ Air Infiltration, WTotal Q, W

2631320.50080.50460.01821.0236

2531320.58430.50460.01821.1071

2431320.66780.50460.01821.1905

2331320.75130.50460.01821.2740

2231320.83470.50460.01821.3575

2130320.91821.00910.03641.9637

2030321.00171.00910.03642.0472

1930321.08521.00910.03642.1307

1530321.41911.00910.03642.4646

1229321.66951.51370.05463.2377

1129321.75301.51370.05463.3212

1229321.66951.51370.05463.2377

1129321.75301.51370.05463.3212

527322.25382.52280.09104.8676

427322.33732.52280.09104.9510

327322.42082.52280.09105.0345

226322.50423.02730.10925.6407

126322.58773.02730.10925.7242

025322.67123.53190.12746.3304

-125322.75473.53190.12746.4139

-224322.83814.03640.14567.0201

-324322.92164.03640.14567.1036

-423323.00514.54100.16387.7098

Total40.902445.91451.655988.4728

Average1.77841.99630.07203.8466

1. Suction Temperature vs. Evaporator TemperatureThe suction pressure and evaporator temperature is recorded for the every changed of the temperature of water inside the tank. While the suction temperature of refrigerant on each interval is the temperature corresponding to the suction pressure at saturated state.Table 1: Suction Temperature vs. Evaporator TemperatureSuction Pressure, psigSuction Temperature, CEvaporator Temperature, CTemperature Difference, C

26-12.909172739.91

31-8.462212735.46

40-1.718562728.72

42-0.324502727.32

42-0.324502727.32

42-0.324502727.32

430.324042726.68

430.324042726.68

430.324042726.68

430.324042726.68

430.324042726.68

430.324042726.68

430.324042726.68

430.324042625.68

41-1.021532627.02

41-1.021532526.02

40-1.718562526.72

40-1.718562425.72

40-1.718562324.72

36-4.5066715.51

33-6.8489717.85

32-7.65559-16.66

31-8.46221-17.46

31-8.46221-17.46

Figure 1. Suction Temperature vs. Evaporator Temperature

The graph shows the relationship between suction and evaporator temperature. Initially, the suction temperature starts in lower range and the evaporator temperature in higher range. As the water changed in temperature, at first the evaporator temperature is constant while the suction temperature increases. Then, the suction and evaporator temperature remains constant up until the water reaches 7C, the suction temperature decrease a little while the evaporator temperature decreases rapidly.

2. Discharge Temperature vs. Compressor TemperatureThe discharge pressure and compressor temperature is recorded for the every changed of the temperature of water inside the tank. While the discharge temperature of refrigerant is the temperature corresponding to the discharge pressure at superheated state.

Table 2: Discharge Temperature vs. Compressor TemperatureDischarge Pressure, psigDischarge Temperature, CCompressor Temperature, CTemperature Difference, C

14038.02114434.98

15341.337586523.66

15541.818746927.18

15541.818747129.18

15541.818747230.18

15541.818747331.18

15541.818747432.18

15541.818747432.18

15541.818747432.18

15541.818747533.18

15541.818747937.18

15241.818748038.18

15040.615848140.38

15942.781058239.22

15241.818748341.18

15040.615848443.38

15040.615848443.38

14940.615848443.38

14840.134688544.87

14539.350998444.65

13536.691297740.31

13636.957267740.04

13837.489207739.51

13837.489207638.51

Figure 2. Discharge Temperature vs. Compressor Temperature

The graph shows the relationship between discharge and compressor temperature. Initially, the discharge and the compressor temperature starts in lower. As the water changed in temperature, the discharge and the compressor temperature increases. Then, the discharge temperature begins to decrease and so the compressor temperature. The initial discharge temperature is greater than the final reading by a little difference while the initial compressor temperature is less than the final reading by a huge difference.

3. Compressor Temperature vs. Condenser TemperatureThe compressor and condenser temperature is recorded for the every changed of the temperature of water inside the tank. The compressor temperature is the temperature reading after the refrigerant pass on the compressor while the condenser temperature is the temperature reading after the refrigerant pass on the condenser.

Table 3. Compressor Temperature vs. Condenser TemperatureCompressor Temperature, CCondenser Temperature, CTemperature Difference, C

43385

653926

693930

713932

723933

733934

743935

743935

743935

753936

793940

803941

814041

824141

833944

843945

843945

843945

853847

843846

773641

773641

773641

763640

Figure 3. Compressor Temperature vs. Condenser Temperature

The graph shows the relationship between compressor and condenser temperature. Initially, the compressor and condenser temperature starts in lower range. As the water changed in temperature, the compressor and condenser temperature increases and the condenser temperature becomes constant. Until it reaches the final, the compressor and condenser temperature decreases in value.

4. Expansion valve Temperature vs. Evaporator TemperatureThe expansion valve and evaporator temperature is recorded for the every changed of the temperature of water inside the tank. The expansion valve temperature is the temperature reading after the refrigerant pass on the expansion valve while the evaporator temperature is the temperature reading after the refrigerant pass on the evaporator.Table 4. Expansion valve Temperature vs. Evaporator TemperatureExpansion Temperature, CEvaporator Temperature, CTemperature Difference, C

92718

102717

112716

112716

112716

112716

112716

112716

112716

112716

102717

102717

112716

112615

102616

102515

92516

92415

92314

716

716

4-15

4-15

4-15

Figure 4. Expansion valve Temperature vs. Evaporator Temperature

The graph shows the relationship between expansion valve and evaporator temperature. Initially, the expansion valve temperature starts in a lower range compare to the evaporator temperature. The expansion valve temperature starts to increase in the middle until it reaches the final where it decreases rapidly. While in the evaporator temperature, where it starts in constant range and decreases little by little in the middle until it reaches final where it decreases rapidly.

5. Temperature of Water vs. Evaporator TemperatureThe temperature of water is recorded for the every changed of it inside the tank. While the evaporator temperature is recorded for the every changed of the temperature of water. The evaporator temperature is the temperature reading after the refrigerant pass on the evaporator.Table 5. Temperature of Water vs. Evaporator TemperatureTemperature of Water, CEvaporator Temperature, CTemperature Difference, C

32275

31274

30273

29272

28271

27270

26271

25272

24273

18279

172710

162711

152712

142612

132613

122513

112514

102414

92314

817

716

6-17

5-16

4-15

Figure 5. Temperature of Water vs. Evaporator Temperature

The graph shows the relationship between the temperature of water and evaporator temperature. Initially, the water temperature and the evaporator temperature starts in a higher range. The temperature of water decreases little by little while the evaporator temperature at first maintains the value of its initial temperature. Until it reaches the finals, the temperature of water still decreases little by little while the evaporator temperature decreases rapidly.