This project is devoted to feasibility study of substitution of LPG (60% Propane and 40 % commercial Butane) as refrigerant instead of R134a in a domestic refrigerator. An experimental performance study on a VCR system
with LPG as refrigerant was conducted and compared with R134a.The VCR system was initially designed to operate with R134a.
2. Ajeet Kumar Rai, Amit Kumar, Pravin Kumar and Ayaj Ahamad Ansari
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employed for medium and low temperature refrigeration. Hydrocarbons were,
however, found extremely inflammable. Dichloromethane, Dichloroethylene and
Monobromomethane were also used as a refrigerant for centrifugal machines. A great
break through occurred in the field of refrigeration with the development of freons.
Freons are a series of fluorinated hydrocarbons, generally known as fluorocarbons,
derived from methane, ethane, etc., as bases. With fluorine, chlorine sometimes
bromine in their molecules, these form a series of refrigerant with wide range of
normal boiling point to satisfy the varied requirements of different refrigerating
machines. The presence of fluorine in the molecule makes the compound non-toxic
and imparts other desirable physical and physiological characteristics. Plank has given
individual treatment to some 50 inorganic and organic refrigerant. Among the most
common inorganic refrigerant are ammonia, water, carbon dioxide. Presently, the
most commonly used organic refrigerant are the chloro-fluoro derivatives of CH4 and
C2H6. The fully halogenated ones with chlorine in their molecule are chloro-
fluorocarbons, referred to as CFCs. Those containing H atoms in the molecule along
with Cl and F atoms are referred to as hydro-chloro-fluoro carbons or HCFCs. Simple
hydrocarbons are HCs, Thus, we have HCs, HFCs, HCFCs and CFCs. Alsaad and
Hammad (1998) investigates the result of an experimental study carried out to
determine the performance of a domestic refrigerator when a propane/butane mixture
is used as a possible replacement to the traditional refrigerant CFC 12. The used
propane/butane mixture is liquefied petroleum gas (LPG) which is locally available
and comprises 24.4% propane, 56.4% butane and 17.2% isobutane. The refrigerator
worked efficiently when LPG was used as refrigerant instead of CFC 12. The
evaporator temperature reached -15C with COP value of 3.4 at a condenser
temperature of 27°C and an ambient temperature of 20°C. Fatouh and Kafafy (2006)
made an attempt to test Liquefied petroleum gas (LPG) of 60% propane and 40%
commercial butane as a drop-in substitute for R134a in a single evaporator domestic
refrigerator with a total volume of 10 ft3 (0.283 m3). Continuous running and cycling
tests were performed on that refrigerator under tropical conditions using different
capillary tube lengths and various charges of R134a and LPG. Continuous running
and cycling results showed that R134a with a capillary tube length of 4 m and charge
of 100 g or LPG with capillary tube lengths from 4.0 to 6.0 and charge of 50 g or
more satisfy the required freezer air temperature of 12 C. The lowest electric energy
consumption was achieved using LPG with combination of capillary tube length of 5
m and charge of 60 g. This combination achieved higher volumetric cooling capacity
and lower freezer air temperature compared to R134a. The performance of the
refrigerator using hydrocarbons as refrigerants was investigated and compared with
the performance of refrigerator when R-134a was used as refrigerant by Sattar et al
(2007). The effect of condenser temperature and evaporator temperature on COP,
refrigerating effect, condenser duty, work of compression and heat rejection ratio
were investigated. The energy consumption of the refrigerator during experiment with
hydrocarbons and R-134a was measured. The results show that the compressor
consumed 3% and 2% less energy than that of HFC-134a at 28°C ambient
temperature when iso-butane and butane was used as refrigerants respectively. The
energy consumption and COP of hydrocarbons and their blends shows that
hydrocarbon can be used as refrigerant in the domestic refrigerator. The present work
has been started with the objective to perform the experimental study on the system
using LPG as refrigerant.
3. Experimental Study on A Domestic Refrigerator Using LPG As A Refrigerant
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2. EXPERIMENTAL SETUP
Figure 1 Photograph of the experimental setup
The above photograph shows the experimental setup. The detailed specifications
of the different components of the setup are given.
Components of domestic refrigerator
Hermetically sealed reciprocating compressor
Type Hermetic reciprocating
Refrigerant R134a
Number of cylinders One
Stroke volume 6.64 cm3
Power supply 1 phase, 220–240 V
Current 6 A (starting), 1.2 (running)
Frequency 50 Hz
Speed 2900 rpm
Air-cooled condenser
Type Wire-on-tube
Tube material Steel
Tube diameter (inner/outer) 4.76/6.18 mm
Outer surface area 0.724m2
Maximum working pressure 40 bar
Evaporator
Type Roll bond-type
Material Aluminium
Length of evaporator panel 1184 ± 1 mm
Thickness of evaporator panel 1.2 ± 1 mm
Passage way surface of panel 0.35 m2
Volume capacity of panel 0.024 m3
4. Ajeet Kumar Rai, Amit Kumar, Pravin Kumar and Ayaj Ahamad Ansari
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Outlet tube diameter 6.5 mm
Maximum working pressure 20 bar
Capillary Tube
Material Copper
Inner diameter 0.78 ± 0.02 mm
Outer diameter 2.0 ± 0.05 mm
Length 2.75 ± 0.03 m
Initial charge (40-90) g
Observation Table
Table 1 Study of performance of 40g LPG as refrigerant in VCR system with 500 g of
water at 29 o
C in evaporator
Time
(min)
Evaporator
temp. T6
(o
C)
Compressor
inlet temp.
T1 (o
C)
Compressor
outlet temp.
T2 (o
C)
Condenser
Outlet temp.
T3 (o
C)
Evaporator
inlet temp.T4
(o
C)
Evaporator
outlet temp.
T5
(o
C)
Suction press.
(Lps)
(Psi)
Discharge
press.
(hps) (Psi)
At start 29 29.2 28 29.4 27.9 28 40 46
2 24.8 28 28.3 30.1 24.4 26.6 4 120
4 23.7 26.8 42.7 34.3 21.8 25.4 2 120
6 22.7 25.8 43.8 35.3 17.8 22.9 0 120
8 21.6 23.3 44.7 35.4 13.6 18.9 0 115
10 19.1 20.8 44.4 35.1 12.5 13.3 0 115
12 17.9 16.6 44.1 35 11.4 12.2 0 110
14 16.8 12.7 43.9 34.8 10.2 11 0 115
16 15.7 10.2 43.9 34.8 9.8 10.1 0 110
18 14.6 9.1 43.9 34.8 9.4 9.8 0 110
20 12.1 8 43.9 34.7 9.7 9.6 10cmHg 110
22 11 7 44.1 34.6 9.2 9.4 10cmHg 110
24 9.9 6.8 44.4 34.6 9 9.3 0 110
26 8.8 6.8 45 34.3 8.9 9.3 0 110
28 7.8 6.4 45.4 34.2 8.9 9.2 10cmHg 110
30 6.8 6.3 45.8 34 8.8 9 10 cm Hg 110
3. RESULTS AND DISCUSSION
In this project LPG gas (used in kitchen for cooking purpose) was used as refrigerant
in domestic refrigerator of 165 litre capacity, basically designed for R-134a as
refrigerant. No alteration has been made by us in the basic design of any component
or capillary length of refrigerator. We tested the performance of refrigerator by
charging 40g of LPG and checked its performance. Experiment has been performed
under load of 500g water kept in steel vessel. Temperature of water, initially was 27
degree Celsius and was brought down at 7 degree Celsius. Reading from various
temperature sensors (fixed at various points), Pressure gauge (fixed at compressor
inlet and compressor outlet), Ammeter and Voltmeter were taken at an interval of two
minutes each. We found that Ammeter reading fluctuates between 0.5A to 1A and
voltmeter reading fluctuated in the range of 210V to 220V. For further calculation we
took these values as 0.5A and 215V as these values were more consistent.
5. Experimental Study on A Domestic Refrigerator Using LPG As A Refrigerant
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Figure 2 compressor temp. vs time graph of 40g LPG refrigerant.
Figure 3 HPS vs time graph of 40g LPG refrigerant.
Figure 4 LP S vs time graph of 40g LPG refrigerant.
0
5
10
15
20
25
30
35
40
45
50
0 5 10 15 20 25 30 35
Compressortemp.(oC)
Time (min.)
108
110
112
114
116
118
120
122
0 5 10 15 20 25 30 35
Highpressureside(Psi)
Time (min.)
-0.5
0
0.5
1
1.5
2
2.5
3
3.5
4
4.5
0 5 10 15 20 25 30 35
Lowpressureside(Psi)
Time (min.)
6. Ajeet Kumar Rai, Amit Kumar, Pravin Kumar and Ayaj Ahamad Ansari
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Figure 5 Evaporator temp. vs time graph of 40g LPG refrigerant.
COP is calculated assuming cycle to be ideal vapour compression cycle and taking
dryness fraction as 0.95.
LPS = 0.69 bar
hf=83.41kJ/kg, hg=516.33 kJ/kg, hfg=432.92 kJ/kg
HPS= 8.28 bar
hg= 593.951kJ/kg= h2, hf = 250.52 kJ/kg= h3= h4
COP= (h1-h4)/ (h2-h1) = 2.45
Experiments were conducted at no load condition, took 6.5 minute to bring down
the Temperature from 300
C to 00
C. Pull down time is 6.5 minutes.
Analysing above data we can infer that LPG charge of 40g worked well at loaded
condition as it took 30 min. to bring down the temperature of 500g of water from 30
degree Celsius to 6.8 degree Celsius in comparison to 90g of R-134a which took 26
min. to bring down the temperature from 27 degree Celsius to 7 degree Celsius.
4. CONCLUSION
The performance of a domestic refrigerator was investigated using LPG as
refrigerants. Although the refrigerator has been designed for 105 g R134a, it was
capable to work with LPG. Nevertheless, energy consumption analysis indicated that
the HFC compressor should be changed to a HC compressor for hydrocarbon
refrigerants. Results showed that energy consumption was reduced, for the
refrigerator while working with a HFC type compressor charged with the optimum
amount of LPG charge, in comparison with the base refrigerator. The proposed LPG
seems to be an appropriate long-term candidate to replace R134a in the existing
refrigerator, except capillary tube length and initial charge Literature review on safety
analysis showed that in case of a sudden leakage of total amount of hydrocarbon
refrigerants, it would not result in explosive conditions. If same experiment was
conducted on the refrigerator designed for LPG, better results are expected.
0
5
10
15
20
25
30
0 5 10 15 20 25 30 35
Evaporatortemperature(oC)
time (min.)
7. Experimental Study on A Domestic Refrigerator Using LPG As A Refrigerant
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