Advanced Research Journals of Science and Technology
ADVANCED RESEARCH JOURNALS OF SCIENCE AND TECHNOLOGY
(ARJST)
Performance Analysis of Domestic Refrigerator With and Without Heat Recovering Unit by using R134a and R600a
2349-9027
Jose Philip1, S.N.CH.Dattu2, V.V Kamesh3 1 Research Scholar, Department of Thermal Engineering,Aditya Engineering College, Surampalem, Andra Pradesh, India. 2 Associate Professor,Department of Mechanical Engineering, Aditya Engineering College, Surampalem, Andra Pradesh, India. 3 Associate Professor,Department of Mechanical Engineering, Aditya Engineering College, Surampalem, Andra Pradesh, India.
Abstract This project presents a study of using different environment friendly refrigerants with zero ozone depletion potential (ODP) and minor global warming potential (GWP), to replace R134a in domestic refrigerator and waste heat recovery from condenser. This work consists of using a hydrocarbon gas mixture which does not deplete ozone layer is ecofriendly, and can be used in the commonly used refrigerators without any significant change in the system of domestic refrigerator. A house hold refrigerator designed to work with R134a was used as an investigation unit to assess the panorama of using R600a refrigerants without any modifications. The recital of the refrigerator using R600a refrigerant was investigated and a compared with the performance of refrigerator when R134a was used as refrigerant. The effect of condenser temperature and evaporator temperature on COP, refrigerating effect was investigated by using both the refrigerants. The energy consumption of the refrigerator during experiment with R600a refrigerant and R134a was measured by using energy meter. The outcome shows the permanent running and cycling results showed that R134a with a charge of 100g or R600a refrigerant with charge of 100mg or more satisfy the required freezer air temperature of -12oC. The main objective of this paper is to study “waste heat recovery system for domestic refrigerator”. An attempt has been made to utilize waste heat from condenser of refrigerator to heat water. This heat can be used for number domestic and industrial purposes. In minimum constructional, maintenance and running cost, this system is much useful for domestic purpose like heating water, heating room, etc. It is valuable alternative approach to improve overall efficiency and reuse the waste heat. The study has shown that such a system is technically feasible and economically viable and also testingtheperformancewithandwithoutheatrecovering unit.
*Corresponding Author: Jose Philip, Research Scholar, Department of Thermal Engineering, Aditya Engineering College, Surampalem, Andra Pradesh, India. Published: December 19, 2015 Review Type: peer reviewed Volume: II, Issue : II Citation: Jose Philip,Research Scholar (2015) Performance Analysis of Domestic Refrigerator With and Without Heat Recovering Unit by using R134a and R600a
INTRODUCTION Heat is energy, so energy saving is one of the key matters from view point of fuel consumption and for the protection of global environment for our future usage. So it is necessary that a significant and concrete effort should be made for conserving energy through waste heat recovery from different machineries. The main objective of this paper is to study “Waste Heat recovery system for domestic refrigerator and performance of refrigerator by using environmental friendly refrigerant”. An attempt has been made to utilize waste heat from condenser of refrigerator to heat water. A domestic refrigerator is a common household Appliance that consists of a thermally insulated compartment and which when works, transfers heat from the inside of the compartment to its external atmosphere so that the inside of the thermally insulated compartment is cooled to a temperature below the ambient temperature of the room. Heat rejection may occur directly to the air in the case of a conventional household refrigerator
having air-cooled condenser or to water in the case of a water-cooled condenser. Tetrafluoroethane (HFC134a) refrigerant was now widely used in most of the domestic refrigerators as the working fluid. THEORY OF REFRIGERATION SYSTEM It has been mentioned before that the refrigeration is defined as the process of removal of heat from a region or state or a substance to reduce and maintain its low temperature and transferring that heat to another region, state or substance at higher temperature by the help of refrigerant which one known as working fluid. The refrigeration process that employed in the domestic refrigerator is based on a vapor compression cycle as shown in Figure 2 and collaborated with Figure 1. There are three main parameter that were considered in this study; compressor power, refrigeration capacity and coefficient of performance (COP).
P-h diagram of vapor compression cycle
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Advanced Research Journals of Science and Technology
Process line from 1 to 2 represents compressor power. Compressor power is defined as the power needed to do the compression process in watt. The compressor power is determined by multiplying enthalpy change across the compressor to the mass flow rate of refrigerant, thus, P=m(h2-h1)
Normal boiling point in O C
-11.6
-26.5
Pressure at -25o C in bar
0.58
1.07
Liquid density At -25o C in kg/l
0.60
1.37
h2 = enthalpy of compressor output (KJ/Kg) h1 = enthalpy of compressor input (KJ/Kg)
Vapor density at t0 -25/+32o C in kg/m3
1.3
4.4
Meanwhile, process from point 2 to 3 represents heat rejection through condenser to atmosphere. Refrigerant get cooled and changed from vapor form to liquid the amount of heat rejected is not significant in the present study. Process from point 3 to point 4 shows throttling effect through capillary tube whereby the working pressure of refrigerant will be reduced from discharge pressure to suction pressure in low pressure region. Refrigeration capacity, which is represented by process line 4 to 1, is defined as the amount of heat absorbed by a unit mass of refrigerant in evaporator from the cooling space. The refrigeration capacity can be obtained using equation below:
Volumetric capacity at -25/55/32o C in kJ/m3
373
658
Enthalpy of vaporization at -25o C in kJ/kg
376
216
Pressure at +20o C in bar (absolute)
3.0
5.7
toxicity
LOW
MEDIUM
Flammability
~460o C - ~470O C(YES)
-800O C
Toxicity after ignition
Extremely Low
Extremely high
Lubricant flammability
~ 200o C
~200o C
Global warming potential
~ 0/3
3100/1300
Ozone depletion potential I
No
No
Atmosphere life time(Years)
<1
~16
Cooling performance @ 40O C
Excellent
Poor
Energy efficiency
High
Low
Power consumption
Low
High
Average system charge by weight
<300 grams
~840 grams
Q=m(h1-h4) h1 = enthalpy of compressor input (KJ/Kg) h2 = enthalpy of evaporator input (KJ/Kg) The coefficient of performance (COP) is a measure of efficiency of the refrigerator. The COP of a domestic refrigerator is the ratio of the refrigeration capacity to the energy supplied to the compressor. It can be expressed by equation below
Refrigerants The last decade has seen drastic changes in the selection and use of refrigerants for refrigeration and air conditioning systems, mainly in reaction to the environmental issues of ‘holes in the ozone layer’ and ‘global warming or greenhouse effect’. Previously there had not been much discussion about the choice of refrigerant, as the majority of applications could be met by the well-known refrigerants. So in this paper am discussing about the usage of R600a which is more ecofriendly than R134a which is commonly using Properties of R-134a and R600a Refrigerants with Comparison Chart Refrigerant
R 600a
R 134a
Class
HC (Hydro carbon)
HFC(Hydro Fluoro Carbon)
Name
Isobutane
1,1,1,2-Tetra Fluoro-Ethane
Formula
(CH3)3CH
CH3-CH2F
Critical temperature in O C
135
101
Boiling point @ 20O C
-29.8O C
-26.6O C
Molecular weight in kg/kmol
58.1
102
EXPERIMENTAL PROCEDURE The following procedure is adopted for experimental setup of the vapor compression refrigeration system. 1. The domestic refrigerator is selected (whirlpool ML1340, 180l), working on vapor compression refrigeration system which using R134a as refrigerant. 2. Pressure and temperature gauges are installed at each entry and exit of the compressor, exit of condenser and inlet of evaporator. 3. Flushing of the system is done by pressurized nitrogen gas. 4. R134a refrigerant is charged into the vapor compression refrigeration system as shown in the above figure. It is charging to the compressor by amount of 100g. 5.Leakage tests are done by using soap solution in every welded portion in order to further the condenser and evaporator pressure and found that there is no leakages which required the absolutely the present investigation to carry out further processing and coated with plastic tapes for safety purpose.
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R134a-Without HRU (Heat Recovering Unit) Time
6. Power on the refrigerator and observation is required for 1 hour and take the pressure and temperature readings at each section in every one hour gap. 7. The performance of the existing system is completed, with the help of temperature and pressure gauge readings those which are connected to compressor inlet and outlet, condenser out and evaporator inlet. 8. The refrigerant is discharged out and condenser is located at the inlet of the capillary tube. 9. Temperature gauge and pressure gauge readings are took and the performance is completed by calculations and values from p-h chart. 10. After that removed R134a and charging R600a to the same system. 11. Then power on and taking values from pressure gauge and thermometer and calculating the cop, that means continuing the process same as R134a 12 After that connected water heater to the outlet of compressor and bottom of condenser tubes, this made with copper coil and again continuing the process from charging R134a (Step 4) Observations and Result Analysis T1=Compressor Inlet Temperature ( C) T2=Compressor Outlet Temperature (o C) T3=Condenser Inlet Temperature (o C) T4=Evaporator Inlet Temperature (o C) o
P1=Compressor Inlet Pressure (bar) P2=Compressor Outlet Pressure (bar) P3=Condenser Outlet (bar) P4=Evaporator Inlet (bar) h1= enthalpy (kJ/kg) according to temperature (T1) and pressure (P1) from p-h chart h2= enthalpy (kJ/kg) according to temperature (T1) and pressure (P1) from p-h chart h3= enthalpy (kJ/kg) according to temperature (T1) and pressure (P1) from p-h chart h4= enthalpy (kJ/kg) according to temperature (T1) and pressure (P1). from p-h chart Net Refrigeration Effect (NRE) = h1-h4 (kJ/kg) Amount of Compressor work= h2-h1 (kJ/kg) Heat removed through condenser= h3-h2 (kJ/kg)
T1 (oC)
T2 (o C)
T3 (oC)
T4 (oC)
P1 (bar)
P2 (bar)
P3 (bar)
P4 (bar)
10AM
20
34
28
2
1.1
12.2
11.3
0.9
11AM
29
42
32
-2
1.4
13.3
11.9
1.2
12PM
31
44
35
-4
1.6
15.3
12.7
1.4
1PM
33
47
36
-6
1.8
16.8
13.3
1.6
2PM
34
50
39
-9
2.1
17.1
14.2
1.9
Time
h1 (kJ/ kg)
h2 (kJ/ kg)
h3 (kJ/ kg)
h4 (kJ/ kg)
h1h4
h2h1
h2h3
COP
Energy Consumption (KWh)
10 AM
380
420
265
160
220
40
155
5.95
1.29
11AM
385
422
269
167
218
37
153
6.18
1.45
12 PM
389
424
272
171
218
35
152
6.22
1.57
1 PM
392
426
275
174
218
34
151
6.45
1.69
2 PM
395
430
280
175
220
35
150
6.75
1.85
R134a-With HRU Time
T1 (o C)
T2 (o C)
T3 (o C)
T4 (o C)
T WATER
P1 (bar)
P2 (bar)
P3(bar)
10AM
24
35
28
0
21
1.2
13.2
12.5
11AM
28
40
30
-2
30
1.7
18.2
16.7
12PM
33
47
32
-6
38
2.1
21.2
17.3
1PM
37
52
34
-8
42
2.4
22.2
18.2
2PM
39
55
36
-11
54
2.8
24.2
19.1
Time
h1 (kJ/ kg)
h2 (kJ/ kg)
h3 (kJ/ kg)
h4 (kJ/ kg)
h1h4
h2h1
h2h3
COP
Energy Consumption (KWh)
10AM
385
420
235
150
235
35
185
6.71
1.13
11AM
390
423
240
158
232
33
183
7.03
1.39
12PM
393
425
243
166
227
32
182
7.09
1.53
1PM
397
428
247
168
229
31
181
7.19
1.70
2PM
400
430
250
170
230
30
180
7.86
1.70
R600a-Without HRU (Heat Recovering Unit) Time
T1 (oC)
T2 (o C)
T3 (oC)
T4 (oC)
P1 (bar)
P2 (bar)
P3 (bar)
P4 (bar)
10AM
21
36
24
1
1.7
19.6
15.3
1.5
11AM
28
40
28
-3
2.3
23.3
17.4
2.1
12PM
33
47
31
-7
2.9
24.1
18.2
2.7
1PM
36
53
33
-12
3.2
24.8
18.9
3.0
2PM
39
58
36
-15
3.4
25.3
19.3
3.2
Time
h1 (kJ/ kg)
h2 (kJ/ kg)
h3 (kJ/ kg)
h4 (kJ/ kg)
h1h4
h2h1
h2h3
COP
Energy Consumption (KWh)
10 AM
580
620
280
185
395
40
340
9.87
.92
11AM
583
623
285
186
397
40
338
9.97
.99
12 PM
587
625
290
190
397
38
335
10.04
1.14
1 PM
589
626
292
192
397
37
334
10.17
1.20
2 PM
590
628
295
195
395
35
150
10.39
1.26
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Percentage Energy Saved
R600a-With HRU Time
T1 (oC)
T2 (o C)
T3 (oC)
T4 (oC)
P1 (bar)
P2 (bar)
P3 (bar)
P4 (bar)
Time
Energy Consumption (KWh) of R134a
Energy Consumption (KWh) of R134a With HRU
% of Energy Saved
10AM
25
35
27
0
21
1.9
20.2
16.3
11AM
33
48
33
-5
30
2.6
24.6
18.9
12PM
36
54
35
-11
38
3.4
28.3
21.2
1PM
39
58
37
-14
42
3.9
29.4
24.3
10AM
1.29
1.13
14.15
28.3
11AM
1.45
1.39
4.31
12PM
1.57
1.53
2.61
1PM
1.69
1.70
-0.588
2PM
1.85
1.70
0.088
2PM
Time
40
62
38
-19
54
4.2
h2h1
h2h3
32.1
h1 (kJ/ kg)
h2 (kJ/ kg)
h3 (kJ/ kg)
h4 (kJ/ kg)
h1h4
COP
Energy Consumption (KWh)
10AM
590
625
275
225
365
36
350
10.42
1.02
11AM
594
632
278
228
366
38
354
10.63
1.02
12PM
605
634
282
230
375
29
352
12.93
1.15
1PM
609
638
288
232
377
29
350
13
1.18
2PM
615
640
290
235
380
25
350
15.2
1.24
Percentage of COP Improved TIME
COP of R134a
COP of R134a with HRU
% of COP improved
10AM
5.95
6.71
12.77
11AM
6.18
7.03
13.75
12PM
6.22
7.09
13.98
1PM
6.45
7.19
11.47
2PM
6.75
7.86
13.48
Percentage of COP improved by using HRU than normal system
Percentage of Energy Savings by using HRU in R134a System Time
Energy Consumption (KWh) of R134a
Energy Consumption (KWh) of R600a
% of Energy Saved
10AM
1.29
.92
40.21
11AM
1.45
.99
46.46
12PM
1.57
1.14
37.71
1PM
1.69
1.20
40.83
2PM
1.85
1.26
46.82
Percentage of Energy Savings by using R600a against R134a Time
Energy Consumption (KWh) of R600a
Energy Consumption (KWh) of R600a with HRU
% of Energy Saved
10AM
.92
.90
14.15
11AM
.99
1.02
-2.94
TIME
COP of R134a
COP of R600a
% of COP improved
12PM
1.14
1.15
-0.869
10AM
5.95
9.87
65.88
1PM
1.20
1.18
1.694
2PM
1.26
1.24
1.612
11AM
6.18
9.97
61.32
12PM
6.22
10.04
61.41
1PM
6.45
10.17
57.67
2PM
6.75
10.39
53.92
Percentage of Energy Savings by using HRU in R600a system Time
Energy Consumption (KWh) of R134a With HRU
Energy Consumption (KWh) of R600a with HRU
% of Energy Saved
Percentage of COP improved by using R600a against R134a TIME
COP of R600a
COP of R600a with HRU
% of COP improved
10AM
1.13
.90
25.55
10AM
9.87
10.42
5.57
11AM
1.39
1.02
36.27
11AM
9.97
10.63
6.61
12PM
1.53
1.15
33.04
12PM
10.04
12.93
28.7
1PM
1.70
1.18
44.06
1PM
10.17
13
28.7
2PM
1.70
1.24
37.09
2PM
10.39
15.2
29.1
Performance improved by using HRU in R600a system TIME
COP of R600a
COP of R600a with HRU
% of COP improved
10AM
6.71
10.42
55.29
11AM
7.03
10.63
51.20
12PM
7.09
12.93
82.36
1PM
7.19
13
80.80
2PM
7.86
15.2
83.43
Percentage of Energy Savings by using HRU with R134a & R600a
Sample Calculations For R134a (Without HRU) (For Set of Values According To 12pm) T1= 31 (o C) P1= 1.6 (bar) h1= 389 (kJ/kg) (Enthalpy values from R134a p-h Chart) T2= 44 (o C) T3= 35 (o C) T4= 4 (o C)
P2= 15.3 (bar) P3= 12.7 (bar) P4= 1.2 (bar)
h2= 424 (kJ/kg) h3= 272 (kJ/kg) h4= 171 (kJ/kg)
Percentage of COP improved by using HRU with R134a & R600a
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Advanced Research Journals of Science and Technology
Net Refrigeration Effect (NRE) = h1-h4 =218 (kJ/kg) Amount of Compressor work= h2-h1 = 35 (kJ/kg) Heat removed through condenser= h3-h2 = 152 (kJ/kg)
Comparison of COP of R134a and R600a both with HRU
Average % of COP improved (By using HRU in R134a System) = 13.07 % Average % of COP improved (By using R600a in R134a System) = 60.04% Average % of COP improved (By using HRU in R600a System) = 19.73% Average % of COP improved (By using HRU in R134a & R600a Systems) = 70.61% Average Energy consumption by R134a without HRU = 1.57 KWh Average Energy consumption by R134a with HRU = 1.49KWh
Comparison of COP of R134a and R134a with HRU
Average Energy consumption by R600a without HRU = 1.12KWh Average Energy consumption by R600a with HRU = 1.12KWh % of energy saving by using R600a in R134a System = 40.17% % of energy saving by using HRU in R600a System = 0% % of energy saving by using HRU in R134a & R600a System = 33.07 % GRAPHS
Comparison of COP of R600a and R600a with HRU
Time vs. Energy consumption in KWh Comparison of COP of R134a and R600a
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Advanced Research Journals of Science and Technology
Experimental Cases
Refrigeration Effect
COP
Energy Consumption
R134a without HRU
218
6.45
1.57KWh
R134a with HRU
230
7.20
1.49 KWh
R600a without HRU
397
10.00
1.12 KWh
R600a with HRU
375
12.50
1.12 KWh
Comparison Table TIME vs. T water Graph
Time vs. Refrigeration Effect
CONCLUSION In the present work experimental investigation is carried out to investigate the performance of vapor compression refrigeration system of a domestic refrigerator of 180 liters capacity, with R134a and R600a as refrigerants in domestic refrigerator with and without HRU. After conducting the experiments, the following conclusions are drawn. Net refrigerating effect is increased by using HRU in domestic Refrigerator by using R134a as refrigerant and light decrease in R600a refrigeration system with and without HRU. Giving more refrigeration effect than R134a by using R600a in both cases. Coefficient of performance is increased by using HRU in Domestic Refrigerator and also R600a giving more COP than R134a. R600a with HRU giving highest COP. Then R600a without HRU, R134a with HRU, least COP given by R134a without HRU. Heat to be rejected in condenser is used to heat water. While using R600a getting more hot water than R134a which shows that it is transferring more heat. Energy Consumption By using R600a is less than Energy consumption By R134a and also with and without HRU, energy Consumption By R600a is same But in R134a with HRU consuming less energy than without HRU. From the above discussions, it can be concluded that the performance of vapor compression refrigeration system of domestic refrigerator is increasing by using water heater for recovering heat. In domestic refrigerator we can directly replace R134a with R600a and the performance is increased by using R600a than R134a. Below tables shows the performance analysis results and energy consumption analysis. From table 6.2 we can conclude that by using HRU we can improve COP and energy savings in both cases of using R134a and R600a. By using R600a in R134a system, we can see that COP and Energy savings are improved. By using R600a, we are getting more performance and energy savings than R134a and it is environmental friendly also. So we can prefer R600a and also HRU also for energy savings.
Experimental Cases
% of COP improved
% of Energy Saved
Energy Consumption
By using HRU in R134a System
13.07
4.114
1.57KWh
By using R600a in R134a System
60.04
42.42
1.49 KWh
By using HRU in R600a System
19.73
2.73
1.12 KWh
By using HRU in R134a & R600a Systems
70.61
35.22
1.12 KWh
Comparison Table
References [1] S C Kaushik and M Singh, Feasibility and design studies for heat recovery from a refrigeration system with a Canopus Heat Exchanger, Heat Recovery Systems and CHP, Vol.15(1995)665673. [2]P Sathiamurthi, P S S Srinivasan, Studies on Waste Heat Recovery and Utilization. Globally Competitive eco-friendlt technologies engineering National Conference(2005)39. [3]P Sathiamurthi, P S S Srinivasan ‘‘Design and Development of Waste Heat Recovery system for air conditioning unit’’, European Journal of Scientific Research,Vol.54 No.1(2011) , pp.102-110. [4]F.N.Yu, K T Chan, ‘‘Improved Condenser design and condenser-fan operation for air-cooled chillers”,Applied Energy,Vol.83(2006)628-648. [5]H.I.Abu-Mulaweh, ‘‘Design and performance of a thermo siphon heat recovery system”,Applied Thermodynamic Engineering,Vol.26(2006)417-477. [6]P Sathiamurthi and R Sudhakaran ‘‘Effective utiluzation of waste water in air conditioner”, Energy and Environmental technologies for sustainable development-Int. Conf.Proc.(2003).
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Author
Jose Philip, Research Scholar, Department of Thermal Engineering, Aditya Engineering College, Surampalem, Andra Pradesh, India.
V.V Kamesh Assistant Professor, Department of Mechanical Engineering, Aditya Engineering College, Surampalem, Andra Pradesh, India.
S.N.CH.Dattu Assistant Professor, Department of Mechanical Engineering, Aditya Engineering College, Surampalem, Andra Pradesh, India.
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