International
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ISSN 0976 – 6359(Online), Volume 5, Issue 8, August (2014), pp. 73-83 © IAEME
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ISSN 0976 – 6340 (Print)
ISSN 0976 – 6359 (Online)
Volume 5, Issue 8, August (2014), pp. 73-83
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IJMET
©IAEME
EXPERIMENTAL INVESTIGATION OF WASTE HEAT RECOVERY
SYSTEM FOR DOMESTIC REFRIGERATOR
TANAJI BALAWANT SHINDE,
SHAILENDRA V. DHANAL,
SHIRISH S. MANE
SSDGCTs, Sanjay Ghodawat Group of Institutions, Atigre, Kolhapur- 416013
ABSTRACT
The objective of this project was to determine the energy savings associated with improved
utilization of waste heat from a domestic refrigerator. Domestic refrigerators maybe operate
continuously to maintain proper food storage condition. The continual operation of this equipment
accounts more electrical energy consumption. Furthermore, a significant amount of waste heat is
rejected by the condensers of refrigerator. The heat rejected by condenser is of low quality, meaning
temperature is low. Thus, practical uses of waste heat from the domestic refrigerators are typically
limited to space heating and water heating. In an effort to more effectively utilize waste heat, the
temperature of the waste heat may be increased, to a limited degree, by raising the condensing
pressure of the refrigeration system. However, studies have shown that raising the condensing
pressure to achieve higher quality waste heat uses more energy than it saves.
The waste heat recovered from a refrigeration system typically consists of either only the heat
which is required to desuperheat the compressor discharge gas, or both the heat required to
desuperheat the discharge gas as well as the heat required to condense the refrigerant. The waste heat
from the former is known as desuperheating waste heat while that from the latter is known as full
condensing waste heat. Less waste heat is recovered through only desuperheating as compared to full
condensing, however the quality of the heat recovered by only desuperheating is higher, i.e., the
temperature of the waste heat from desuperheating is higher than that obtained from full condensing.
The main objective of the project is to utilize the waste heat of the condenser by desuperheating of
compressor discharge gas. The project work also aims at,
- Fabrication, Experimentation and performance evaluation of Waste Heat Recovery System under
the following test conditions,
1) Refrigerator 2) Refrigerator-cum-Water Heater
Experimentally it is found that waste heat recovery from domestic refrigerator is technically feasible
and economically viable.
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International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 – 6340(Print),
ISSN 0976 – 6359(Online), Volume 5, Issue 8, August (2014), pp. 73-83 © IAEME
Keywords: Domestic Refrigerator, Desuperheating, Refrigerator-Cum-Water Heater, Performance.
INTRODUCTION
Waste heat recovery depends upon the various sources of application and temperature range.
It broadly classified as given in table1 below,
Sr.
No.
1
2
3
Table 1: Heat recovery sources and its temperature range
Type of heat
Remark
Recovery
High Temperature
These type of heat recovery results from direct fuel fired
Heat Recovery
processes of industrial process equipment in the high
o
temperature range.
(650-1650 C)
Medium Temperature Most of the waste heat in this temperature range comes from the
Heat Recovery
exhaust of directly fired process units in medium temperature
o
range.
(230-650 C)
These type of heat recovery results from bearings, welding
Low Temperature
machines, injection molding machine, Annealing furnaces,
Heat Recovery
forming dies, Air compressor, pumps, Internal combustion
o
engine, Air conditioning and refrigeration condensers, Drying,
(27-230 C)
baking and curing ovens, Hot processed solid or liquid etc.
A household 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 environment 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.
Heat can be recovered by using the water-cooled condenser and the system can work as a
waste heat recovery unit. The recovered heat from the condenser can be used for bathing, cleaning,
laundry, dish washing etc.
Typical waste heat temperature for Air conditioning and refrigeration condensers are 32 to 43
o
C. Low temperature waste heat may be useful in a supplementary way for preheating purposes.
Keeping this in mind, a technique for condensing heat of the refrigeration system is proposed in this
paper. The proposed system employs a combined air and water-cooling (desuperheating) technique
for condensing heat of refrigeration system. This new system provides not only the refrigeration
effect, but also hot water.
LITERATURE REVIEW
S.C. Kaushik [1] et al presents an investigation of the feasibility of heat recovery from the
condenser of a vapour compression refrigeration (VCR) system through a Canopus heat exchanger
(CHE) between the compressor and condenser components. The presence of the CHE makes it
possible to recover the superheat of the discharged vapour and utilize it for increasing the
temperature of the external fluid (water) removing heat from the condenser. The effects of the
operating temperatures in the condenser and evaporator for different inlet water temperatures and
mass flow rates on the heat recovery output and its distribution over the condenser and CHE (the
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International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 – 6340(Print),
ISSN 0976 – 6359(Online), Volume 5, Issue 8, August (2014), pp. 73-83 © IAEME
fraction of the condenser heat available through the CHE), available outlet water temperature and
heat recovery factor have all been studied and optimum operating parameters for feasible heat
recovery have been ascertained. The parametric results obtained for different working fluids, such as
R-22, R-12, R-717 and R-500, have been presented. It is found that, in general, a heat recovery factor
of the order of 2.0 and 40% of condenser heat can be recovered through the Canopus heat exchanger
for a typical set of operating conditions.
Dr.M.S.Tandale presented a case study on Super Heat Recovery Water Heater At Worli,
Dairy. They used R717 Kirloskar Reciprocating Compressor having refrigeration system capacity of
270 TR (950KW). The Inlet & Outlet temperature of Refrigerant are 115 & 60°C.The Inlet & Outlet
temperatures of Water are 25 & 70°C. They installed super heat recovery water heater in counter
current mode. The hot water flow rate is 70000 L/day. In this system fuel saving is about 390 l
FO/day. The annual saving is near about Rs.23 Lac/year. Also the reduction in CO2 emissions is 330
ton/year.
EXPERIMENTAL SETUP
Experimental setup consists of 200 L capacity, single door LG refrigerator. The system was
retrofitted with a water tank having capacity of 2 L. The refrigerator is having a vertical cabinet. A
tank made-up of MS is fitted at the beginning of the condenser line. A partial portion of the
condenser line is immersed in the tank for desuperheating of refrigerating gas. The volume of water
used for testing is 2L.A water in tank was kept stationery till water get temperature more than 40 0C.
An instrument panel made-up of MS is used for mounting gauges. Pressure gauges indicating suction
pressure of compressor and pressure after condensation. Also an energy-meter has been used to
measure the energy consumption. A temperature sensor set has been used to monitor various
temperatures encountered in the system. Symbols used for indicating temperatures are listed below,
Symbol
T1
Component
Temperature after evaporation, C
T2
Temperature after compression, C
T3
Temperature after condensation C
o
Symbol
T4
Temperature after throttling, C
T6
Water inlet temperature, C
T7
Water outlet temperature, C
o
o
Component
o
o
o
Fig1: Schematic diagram of the experimental setup
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International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 – 6340(Print),
ISSN 0976 – 6359(Online), Volume 5, Issue 8, August (2014), pp. 73-83 © IAEME
Photo1.Refrigerator condenser immersed
in water tank for desuperheating.
SpecificationsCondenserM S coil
Inner dia. 3mm, Outer dia. 5mm
Length 4.5metre
TankM S sheet
Size 120mm x 105mm x 280mm
Photo1 Desuperheating
Photo 3.Hermetically sealed compressor
Model: MA42LBJG
Min. pressure: 8psi
Max. Pressure: 140psi
Refrigerant-R134a
Photo 3.Hermetically sealed compressor
Photo 4.Instrument control and display Panel
1. Temperature Indicator ‘Sensography’ make 12 point single phase temperature
indicator 92 x 92 cutout,
Range – (-30 to 150 0C)
2. Temperature sensing element
Thermocouple wire 1/36” gauge
‘K’ type Cr-Al type
Range – - 50 0C to 400 0C
Quantity – @ 9 meter
3. Pressure gauge
‘WIKA’ make
Range – 0 to 28 kg/cm2
4. Energymeter
240 V, 5-30 A, CL 1, 50 Hz, 3200 imp/kWhr
Photo 4.Instrument control and display Panel
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International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 – 6340(Print),
ISSN 0976 – 6359(Online), Volume 5, Issue 8, August (2014), pp. 73-83 © IAEME
EXPERIMENTAL PROCEDURE
Fig.1 shows the scematic diagram of experimental setup. After the installation of the
components on refrigerator test setup started.Test was conducted in two phases which are as follows-
No Load (Refrigerator door fully closed), with and without water
Full Load (Refrigerator door fully opened), with and without water
At each load conditions temperature and pressure at salient points were noted down at every
thirty minutes interval. The initial and final temperature of the water also measured.The test were
conducted until steady state is reached.To find out energy consumption energymeter reading were
noted.for finding out the coefficient of performance compressor suction and discharge pressure were
used.Once equilibrium temperature were reached between water and condensing temperature it was
found that,there is no more change in temperature of water.The water temperature was upto
satisfactory level or preheated state.once water got preheated state the water tank filled fresh water
and procedure repeated.
RESULTS AND DESCUSSION
The graphs plotted below indicate an increase in the outlet temperature of water with time.
The temperature rise varies according to type of load applied. The power consumption decreases
with an increase in outlet temperature. The graphs also indicate an increase in the Coefficient of
Performance. The COP decreases with an increase in time. Thus as time increases, the COP
decreases and remains constant after a certain interval of time.
The overall temperature difference encountered at the end of 30 minutes exceeds 10 0C . Thus, with
an increase in the time interval the outlet water temperature can be increased considerably.
Temperature Vs Time (No load with water)
Water Temperature (degree C)
Temperature Vs Time
(No load with water)
45
40
40.7
39.8
37.8
35
Temperature Vs Time
(No load with water)
34.6
30
25
0
10
20
30
40
Time (min)
Graph.1: Temperature Vs Time (No load with water)
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International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 – 6340(Print),
ISSN 0976 – 6359(Online), Volume 5, Issue 8, August (2014), pp. 73-83 © IAEME
Power Vs water temperature (No load with water)
Power Vs water temperature
(No load with water)
Power (kw)
0.20
0.12
0.11
0.10
Power(kw) Vs
water temperature
0.11 0.11
0.00
34
36
38
40
42
Water Temperature (degree C)
Graph.2: Power Vs water temperature (No load with water)
Temperature Vs Time (Full load with water)
Water Temperature (degree C)
Temperature Vs Time
(Full load with water)
50
47.5
45
44.6
40
Temperature Vs
Time(Full load with
water)
39.9
35
34
30
25
0
10
20
30
40
Time (min)
Graph 3: Temperature Vs Time (Full load with water)
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International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 – 6340(Print),
ISSN 0976 – 6359(Online), Volume 5, Issue 8, August (2014), pp. 73-83 © IAEME
Power Vs water temperature (Full load with water)
Power Vs water temperature
(Full load with water)
0.20
Power (kw)
0.18
Power Vs water
temperature (Full
load with water)
0.12
0.12
0.10
0.10
0.00
30
35
40
45
50
Water Temperature (degree C)
Graph.4: Power Vs water temperature (Full load with water)
COP Vs Time (No load with and without water)
Graph.5: COP Vs Time (No load with and without water)
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International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 – 6340(Print),
ISSN 0976 – 6359(Online), Volume 5, Issue 8, August (2014), pp. 73-83 © IAEME
COP Vs Time Full load with and without water
Graph.6: COP Vs Time Full load with and without water
SPECIMEN CALCULATIONS
Density of water, ࣋ = 1000 kg/m3
Specific heat of water,Cpw = 4.18 kJ/kg-K
Specific heat of refrigerant,Cpr = 1.51 kJ/kg-K
Volume of water, V= 2 ltr = 0.0002 m3
All temperatures in degree C and pressures in kg/cm2
For finding out the COP of the system, the enthalpies at all the points of the cycle must be known.
These enthalpies are noted from the p-h chart of the concerned refrigerant.
1) The refrigerating effect is calculated as,
Re = h1-h4 kJ/kg
2) The work done per kg of refrigerant is given by,
W= h2-h1 kJ/kg
3) The coefficient of performance is given by,
COP = (Re/W) = (h1-h4/ h2-h1)
4) The coefficient of performance using Carnot cycle is given as,
COP (Carnot) = (Te/Tc-Te)
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International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 – 6340(Print),
ISSN 0976 – 6359(Online), Volume 5, Issue 8, August (2014), pp. 73-83 © IAEME
5)Also,
Heat gained by evaporator,Qe = h1-h4 kJ/kg
Heat rejected by condenser,Qc = h2-h3 kJ/kg
6) Now, to calculate heat gained by water
Qw = (ρ*v*Cpw*∆T)/t kW
7) The power consumption is calculated as,
P = (3600*n) / (EM constant * time for n pulses) kW
8) The temperature difference is calculated as,
∆T = (T7-T6) 0C
I-Condition: Refrigerator-cum-Water Heater with NO LOAD
1) The refrigerating effect is calculated as,
Re = h1-h4 kJ/kg = 113 kJ/kg
2) The work done per kg of refrigerant is given by,
W= h2-h1 kJ/kg = 57 kJ/kg
3) The coefficient of performance is given by,
COP = (Re/W) = (h1-h4/ h2-h1) = (113/57) = 2.0175
4) The coefficient of performance using Carnot cycle is given as,
COP (Carnot) = (Te/Tc-Te) = ((-20+273) / (54+20)) = 3.42
5)Also,
Heat gained by evaporator,Qe= h1-h4 kJ/kg = 113 kJ/kg
Heat rejected by condenser,Qc= h2-h3 kJ/kg = 180 kJ/kg
6) Now, to calculate heat gained by water
Qw=(ρ*v*Cpw*∆T)/t kW = (1000*2*4.187*10.7) / (1000*30*60) = 0.0496 kW
7) The power consumption is calculated as,
P= (3600*n) / (EM constant * time for n pulses) kW = (3600*10) / (3200*80.4) = 0.13992 kW
8) The temperature difference is calculated as,
∆T = (T7-T6) 0C = 0.9
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International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 – 6340(Print),
ISSN 0976 – 6359(Online), Volume 5, Issue 8, August (2014), pp. 73-83 © IAEME
II-Condition: Refrigerator-cum-Water Heater with FULL LOAD
1) The refrigerating effect is calculated as,
Re = h1-h4 kJ/kg = 109 kJ/kg
2) The work done per kg of refrigerant is given by,
W = h2-h1 kJ/kg = 59 kJ/kg
3) The coefficient of performance is given by,
COP = (Re/W) = (h1-h4/ h2-h1) = (109/59) = 1.84746
4) The coefficient of performance using Carnot cycle is given as,
COP (Carnot) = (Te / Tc-Te) = ((-20+273) / (54+20)) = 3.42
5) Also,
Heat gained by evaporator,Qe = h1-h4 kJ/kg = 109 kJ/kg
Heat rejected by condenser,Qc = h2-h3 kJ/kg = 168 kJ/kg
6) Now, to calculate heat gained by water
Qw = (ρ*v*Cpw*∆T)/t kW = (1000*2*4.187*7.5) / (1000*30*60) = 0.0348333 kW
7) The power consumption is calculated as,
P = (3600*n) / (EM constant * time for n pulses) kW = (3600*10) / (3200*72) = 0.15625 kW
8) The temperature difference is calculated as,
∆T = (T7-T6) 0C = 2.9 0C
CONCLUSION
It can be concluded that the system while operating under full load condition gives a better
COP as compared to no load condition. Hence if the system continuously operates under full load,
the COP can be improved. The heat absorbed by water has been observed to be maximum during full
load. The heat recovery technique, which can be applied to a refrigeration system provides a
compound air-cooling and water-cooling. The use of heat recovery system illustrates the
improvement in COP and also the reduction in power consumption. The temperature difference
obtained between the water inlet and outlet exceeds 10 0C . Thus a more optimum and efficient
system can be built to give better results. The heat recovery module can thus be used in various
refrigeration applications as well as in air conditioning.
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International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 – 6340(Print),
ISSN 0976 – 6359(Online), Volume 5, Issue 8, August (2014), pp. 73-83 © IAEME
REFERENCES
A. Journals
[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,
Volume 15, Issue 7, October 1995, Pages 665-673.
[2] G.E. Stinson, C.J. Studman and D.J. Warburton, ‘The performance and economics of a dairy
refrigeration heat recovery unit’, Agricultural Engineering Department, Massey University,
Palmerston North, New Zealand, Journal of Agricultural Engineering Research, Volume 36,
Issue 4, April 1987, Pages 287-300.
B. Reference Books
[1] Yunus A. Çengel, “Heat and Mass Transfer: Practical Approach (Si Units)”, Third Edition,
Tata McGraw-Hill publication. 2000.
[2] Arora, Domkundwar ,”A Course in Refrigeration and Air Conditioning”, Dhanpat Rai & Co.
(P) Ltd., pg. 4.1 to 4.48 and 5.1 to 5.81.
C. Websites
[1] www.sciencedirect.com
[2] www.ASHRAE.com
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