International Journal of Engineering Trends and Technology (IJETT) – Volume 12 Number 6 - Jun 2014
Improvement in Coefficient of Performance of
Domestic Refrigerator Using Flash Chamber
Authors: Dheeraj, Manik Kataria, Saharsh Misra, Saurabh Bhatia, S.K Gupta
Department of Mechanical and Automation (MAE), Guru Gobind Singh Indraprastha University, Dwarka, New Delhi, India
Abstract — This paper investigates the impact of flash chamber
on the performance of household refrigerators. In this novel flash
chamber concept, the liquid and vapour is segregated before
entering the evaporator which results in improvement in the
coefficient of performance of the system. In minimum
construction, maintenance and running cost, this attempt is quite
useful for domestic purpose. Since environmental pollution and
energy costs are on a rise, therefore, this concept is a way
forward in realizing the economic as well as environmental
demands. As it’s coherently said, the energy saved is the energy
produced.
Keywords— Refrigerator, Flash Chamber, COP, Environment,
Pollution, Environment, Energy saving, Refrigerant
(COP) without F.C =
h1 – h4
h 2 – h1
(COP) with F.C =
h1 – h5
h2 – h1
Increase in COP = (COP) with F.C. – (COP) without F.C.
I. INTRODUCTION
=
Refrigerator is treasured as one of the best innovations
of the 20th century. It has become one of the prime necessities
of the 21st century. In over a span of three decades, there has
been a surge in the energy demands due to the ever increasing
population esp. in India. This has led to increased pollution
and energy costs. The World Health Organization (WHO)
estimates that about a quarter of the diseases facing mankind
today occur due to prolonged exposure to environmental
pollution. The idea of this project explores the possibility of
improvement in COP of refrigerator by the incorporation of a
flash chamber. R134a, the most common and eco-friendly
refrigerant was adopted as the refrigerant for this project.
Using a standard domestic refrigerator, the conceptual design
revolves around extending a hydraulic circuit in which a
liquid-vapour refrigerant separator known as Flash chamber is
installed. The thermodynamic calculations are obtained with
the help of pressure gauges and digital temperature meters
installed in the circuit.
(h1 - h5 – (h1 - h4))
h2 - h1
=
h 4 - h5
h2 - h1
Since,
Refrigerating effect with F.C. (h1-h5) > Refrigerating effect
without F.C. (h1-h4)
Hence, (COP) with F.C > (COP) without F.C
II. THEORY
Modified vapour compression system consists of compressor,
condenser, expansion device, evaporator and a flash chamber.
The operation cycle involves compressing a low pressure
vapour refrigerant to a high temperature-high pressure vapour
(process 1-2); condensing the high pressure vapour to a high
pressure liquid (process 2-3); expanding the high pressure
liquid to a low pressure and low temperature liquid-vapour
mixture (process 3-4); separating the liquid and vapour using
a flash chamber and evaporating the low pressure liquid to the
low pressure vapour (process 5-1).
ISSN: 2231-5381
Fig. 1 P-h diagram for refrigeration cycle without flash chamber
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International Journal of Engineering Trends and Technology (IJETT) – Volume 12 Number 6 - Jun 2014
III. SYSTEM DESCRIPTION
In the selected 165 litres domestic refrigerator, the
refrigerant's flow path has been modified by the use of ¼ inch
copper pipes. The hydraulic circuit including the flash
chamber has been designed to bifurcate and navigate
refrigerant's flow. The flash chamber is of ¾ inch diameter
and is 8 inches long copper pipe. Also a sight glass is
incorporated in the flash chamber circuit to keep a check on
the presence of liquid refrigerant in the vapour branch of the
flash chamber circuit.
.
Fig. 2 P-h diagram for refrigeration cycle with flash chamber
A. Effect of Condenser Temperature
Also, 5 gate valves have been incorporated to switch between
the original and modified circuit. There are 5 pressure gauges
and 3 digital temperature meters in the extended modified
circuit which indicate pressures and temperatures respectively.
IV. EXPERIMENTATION AND MEASUREMENT
The condensing temperature also enforces the improvement
in COP.
In, summer or extremely hot days, the room/ surrounding
temperature is bound to rise. The rise in the surrounding
temperature leads to a shift in the compressor outlet state
(2
2’) and hence a shift in the state (4
4’).
The following diagram shows the effect of condenser
temperature on COP :
A Godrej refrigerator of 165l capacity is used for the
development of experimental system.
TABLE I
SPECIFICATIONS OF SYSTEM
Refrigerant
Compressor : Rated Cooling
Capacity
Power Input
Displacement
Voltage
Condenser
R134a
107watts
102 watts
4.16cc
220
Air Cooled Condenser
The refrigerator test setup investigates the performance of the
system. In developing a reliable refrigerator test setup,
consideration should be highly addressed to the development
method and points of measurement of pressures and
temperatures.
Fig. 3 Effect of condenser temperature on COP.
The experimental test results show that as extreme summer
approach, the percentage increase in COP tends to rise.
COP new
=
COP old
=
Hence,
h1 – h4’
h2’ – h1
h1 – h4
h2 – h1
+
+
h4’ – h5
h2’ – h1
h4 – h5
h2 – h1
COP new > COP old
ISSN: 2231-5381
The refrigerator is equipped with three basic instrumentation
systems. The temperature meters and pressure gauges measure
the thermodynamic properties in the system. The Sub-meters
measure the power consumption of the compressor.
There are 5 points of pressure measurement and 3 points of
temperature measurement. Since the objective of this work is
to improve the COP of the domestic refrigerator using flash
chamber, therefore it is also closely related to refrigeration
capacity and compressor power produced by the system.
A typical test run involved putting the load in freezer. Usually
it would take 40 to 60 minutes for the system to reach steady
state. Some care should be taken in deciding if the refrigerator
has reached steady state.
For these tests, steady state conditions were assumed if after
40 minutes, the average pressures did not vary by more than 1
psi during that time period. It was found that if shorter time
periods were taken such as 10 minutes, it would appear that
steady state conditions had been reached when in fact the
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International Journal of Engineering Trends and Technology (IJETT) – Volume 12 Number 6 - Jun 2014
pressures were still changing. Data was collected every twenty
minutes for a minimum of at least one hour.
The cost of inclusion of flash chamber circuitry is
approximately Rs.220.
Considering electricity slab rate in Delhi as Rs.3.90/unit,
there is a saving of 0.507/day/refrigerator; we conclude that
the payback time period for the cost of modification in
circuitry if commercialized is 14 months, assuming that
electricity saving is 3-4% though out the compressor operation.
Presuming the refrigerator compressor works for 24
hours per day and on Flash Chamber circuit, the energy
consumption is 2.8kWh. Therefore, the refrigerator consumes
2.8 units of electricity per day, whereas, a normal domestic
refrigerator consumes 2.93 units of electricity per day under
the same conditions.
Presuming 10 million refrigerators units all over the country,
about 1.3 million units of electricity are being saved per day
and generation of several tons of CO2 is also prevented.
Fig. 5 Variation of COP with time in both without flash chamber and with
flash chamber circuits.
Fig. 4 Schematic diagram of the modified circuit including flash chamber.
V. RESULTS AND DISCUSSIONS
The Coefficient of Performance of domestic refrigerator after
the incorporation of Flash Chamber was increased by 48.57%
and the savings in the power consumption was about 3-4 %.
The routine tests involved an operating time of 100
minutes. Savings in power consumption are expected to
increase upto 10-15% due to the early cut-off of the
compressor. The instrumental errors in pressure gauges and
temperature gauges have been neglected in the calculations.
The experimental tests were performed during the month
of May in New Delhi, when the room temperature observed
on digital temperature meter was 31.7 degree Celsius. As
extreme summers approach, it was observed that the
condenser operated at higher temperatures.
ISSN: 2231-5381
ACKNOWLEDGMENT
We wish to express our profound gratitude to Prof. S.K Gupta,
HOD-Department of Mechanical & Automation Engineering,
HMR Institute of Technology & Management for introducing
the present topic and for his inspiring guidance, constructive
criticism and valuable suggestions throughout the project
work.
We are also indebted to the management of “HMR Institute of
Technology and Management” for lending us various
resources and constant support throughout.
It is imperative to say that our research and experiment would
not have been successful without the immense help from the
above mentioned people.
REFERENCES
[1]
[2]
C.P Arora, Refrigeration and air-conditioning notes.
[Online] site links. Available:
https://www.ideals.illinois.edu/handle/2142/18510
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