This work shows the effect phase change material (PCM) on temperature fluctuation inside the evaporator cabinet of a household refrigerator. The experiment has been done at different thermal loads with two different PCMs (Water and Eutectic solution (90% H2O + 10% NaCl) of melting point 0°C and -5°C respectively). The PCM is placed around the five sides of the evaporator cabinet in which the evaporator coil is immersed. The experimental results with PCM confirm the notable reduction of the fluctuation of the cabin temperature at lower load but at higher load this effect is not so significant. Between two PCM, the reduction of temperature fluctuation for Eutectic solution is better than water PCM. This reduction of temperature fluctuation ultimately improves the food preservation quality of the refrigerator

1. International Journal of Recent advances in Mechanical Engineering (IJMECH) Vol.3, No.1, February 2014
43
DIMINUTION OF TEMPERATURE FLUCTUATION INSIDE
THE CABIN OF A HOUSEHOLD
REFRIGERATOR USING PHASE CHANGE MATERIAL
Md. Imran Hossen Khan1
and Hasan M.M. Afroz2
1,2
Department of Mechanical Engineering, Dhaka University of Engineering &
Technology, Gazipur, Bangladesh
ABSTRACT
This work shows the effect phase change material (PCM) on temperature fluctuation inside the evaporator
cabinet of a household refrigerator. The experiment has been done at different thermal loads with two
different PCMs (Water and Eutectic solution (90% H2O + 10% NaCl) of melting point 0°C and -5°C
respectively). The PCM is placed around the five sides of the evaporator cabinet in which the evaporator
coil is immersed. The experimental results with PCM confirm the notable reduction of the fluctuation of the
cabin temperature at lower load but at higher load this effect is not so significant. Between two PCM, the
reduction of temperature fluctuation for Eutectic solution is better than water PCM. This reduction of
temperature fluctuation ultimately improves the food preservation quality of the refrigerator.
KEYWORDS
Food preservation, Household refrigerator, Phase change Material, Temperature fluctuation, Cabinet
1. INTRODUCTION
Household refrigerator or cold storage is playing an important role for preserving our daily food
and it is better than most of other preservation methods. But the most important problem in this
process is to exposure higher temperatures and/or fluctuations of storage temperature produces
cumulative adverse effects on the quality of stored foods, which is the primary cause of damage
to food marketed through retail channels [1]. In the conventional household refrigerator the
compressor works in on-off mode. The refrigerant of the evaporator coil takes the cabinet heat
during compressor on mode. During the off mode of the compressor, the temperature inside the
evaporator cabinet starts rising due to heat released by the food and also due to ambient
conditions. This on and off makes a temperature fluctuation (temperature rapidly rise and drop)
inside the evaporator cabinet which ultimately decrease the quality of the food. The physical and
chemical changes caused the loss of quality of the product. Due to temperature fluctuation
occurred during the storage period of frozen vegetables and fruits, which changes the physical
structure of that food which ultimately affect the quality are a result of re crystallization and
sublimation phenomena, related to the stability of the ice crystals inside and on the surface of the
products. Temperature fluctuations during freezing are prior responsible of that re- crystallization
and surface drying, although the importance of these physical changes decreases at lower storage
temperatures [2] [3][4]. Flores and Goff [5] found that the size of ice crystals was larger in
samples stored under fluctuating conditions compared to storage at a constant temperature.
Donhowe and Hartel [6] studied the ice re-crystallization during bulk storage of ice cream in
containers. They controlled the freezer temperature with ±1.0 ºC fluctuation and without

2. International Journal of Recent advances in Mechanical Engineering (IJMECH) Vol.3, No.1, February 2014
44
fluctuations ±0.01 ºC, within the temperature range between -15 and -5 ºC. They concluded that
re-crystallization rate increased with storage temperature and extent of temperature fluctuations.
Phimolsiripol et al. [7] also studied the temperature fluctuations effects on frozen dough and
bread quality during frozen storage. They found the weight and the quality of that food has been
lost significantly due to temperature fluctuation occurred during freezing. Gormley et al. [8]
studied some quality parameters of selected food products during freezing with and without
fluctuating the temperature inside the freezer. Their result shows that the food is damaged by
thermal stress and deleterious effects such as fat oxidation and changes in colour and texture due
to temperature fluctuations.
So reduction of temperature fluctuation inside the evaporator cabinet, i.e. make a continuous or
stable temperature inside the cabinet would be the most important issue in terms of designing a
household refrigerator.
Using phase change material (PCM) could be a nice option for reduction of temperature
fluctuation inside the evaporator cabinet. A phase change material (PCM) is a latent heat
thermal energy storage system which, melting and solidifying at a certain temperature. During the
phase change time the material is capable of storing and releasing large amounts of heat energy
and that’s why it is called heat storage system (LHS). Some example of PCM are given in the
Table-1
Table. 1 List of some phase change materials with their melting point and latent heat of
fusion
PCMs Melting point (0
C) Latent heat of fusion (kJ/kg)
H2O 0.0 333
SbCl5 4.0 33
POCl3 1.0 85
Na2SO4 + NaCl +KCl + H2O
(31+13+16+40) wt %
4.0 234
NaCl (22.4 wt.%) /H2O -21.2 222
KCl (19.5 wt.%) / H2O -10.7 283
n-Tetradecane 5.5 226
n-Pentadecane 10 207
Working mechanism of PCM in a household refrigerator:
In the conventional household refrigerator the compressor works in on /off mode. The refrigerant
of the evaporator coil takes the cabinet heat during compressor on mode. Actually during the off
mode of the compressor or when the power failure happens which is very common in many
developing countries like Bangladesh, the temperature inside the evaporator cabinet starts rising
due to heat released by the food and also due to ambient conditions. If PCM is used in the cabinet
then it will take most of the heat by changing its phase from solid to liquid. It maintains a
constant temperature until the melting process is completed. Thus for a certain period of time
(until the PCM melts completely) the desired temperature of the product can be maintained
during the off cycle of the compressor which ultimately prolonged the off cycle.
Taking account of the benefits of PCM many researchers are using this PCM in a household
refrigerator. Maltini et al. [9] experimentally investigated effect of sodium chloride–water
mixture as cooling storage system on a household refrigerator. The observed that the PCM
behaved as a temperature damper which ultimately minimized the temperature fluctuations and
improved the quality of preservation of food. For economical and environmental considerations,
phase change materials are used in many applications [10], such as food or pharmaceutical

3. International Journal of Recent advances in Mechanical Engineering (IJMECH) Vol.3, No.1, February 2014
45
products preservation, storage devices in thermal conversion systems. Subramaniam et al. [11]
designed and investigate the effect of PCM on temperature fluctuation on dual evaporator
refrigerator and found the refrigerator with PCM to improve food quality and prolong compressor
off time. Marques et al. [12] developed a model to investigate the performance improvement
provided by a phase change material associated with the evaporator in a domestic refrigerator.
The compressor performance analysis demonstrated that larger displacement compressors are
more efficient. An effective way to exploit this higher performance is to accumulate the excess
cooling capacity in a PCM. A further advantage of a larger compressor is that the increased
cooling capacity enables more rapid freezing of the PCM. This will permit the compressor off-
cycle time to be increased, thereby saving energy. The PCM heat release and storage model
showed that the melting and freezing time increases proportionally with PCM thickness. The
refrigerator autonomy was strongly affected by the refrigerator heat load and compressor cooling
capacity. An increase in ambient temperature from 20 to 43 °C resulted in a 47 % reduction in
autonomy. K. Azzouz et al. [13] made a simulation of a system of household refrigerator with
PCM. The simulation results of the system with PCM show that the energy stored in the PCM is
yielded to the refrigerator cell during the off cycle and allows for several hours of continuous
operation without power supply. K. Azzouz et al. [15] experimentally investigated the
performance of a household refrigerator by using phase change material. The experimental results
indicate that the integration of latent heat storage allows 5-9h of continuous operation without
electrical supply which ultimately didn’t allow to increasing the temperature inside the cabin.
More recently, Gin et al. [16] investigated a refrigerator with PCM which is placed against the
internal walls of the freezer and they concluded from their result, it is possible to maintaining a
stable temperature inside the refrigerator in the presence of heat loads. Furthermore they observed
that the introduction of PCM has improved the quality of the frozen foods during the storage [17].
The studies that have been reported in the literature on the behaviour of a refrigerator coupled
with a phase change material as a slab applied on the backside of the evaporator or the PCM slab
which is placed inside the cabin. Concerning that the purpose of the present work is set to remove
the problem of third material between the PCM and cooling coil by installing the evaporator coil
into the PCM box so that the evaporator coil directly contacts with the PCM material as immersed
condition. As a result higher conduction heat transfer is expected to obtain. Also the PCM
materials have been used in the five sides of the evaporator chamber. Moreover, the PCMs and
operating conditions (thermal load, cabinet setting temperature, and quantity of PCM) that are
used in this experiment are different from the above discussed experiment to reveal their detail
effects on refrigeration cycle performance.
2. EXPERIMENTAL METHODOLOGY
A conventional household refrigerator is used in the modified form with PCM box located behind
the evaporator cabinet to carry out the necessary experiments. The experimental set up comprised
with a refrigerator, pressure transducer, pressure gauge, thermocouple, phase change material
box, and data acquisition system. Figures 1 and 2 show the details of the location of the PCM box
with the evaporator cabinet. The PCM box is made up by galvanized iron (GI) sheet have 1 mm
thickness, which is 0.56 m width, 0.44 m height and 0.47 m depth. The evaporator cabinet box of
outer volume 0.04 m3
with cooling coil [Fig. 1(a)] is inserted into the empty PCM box of internal
volume 0.11 m3
[Fig. 1(b)]. The thickness of the annular space between PCM box and evaporator
cabinet box is 0.006m. The open face of the annular space is sealed by a third sheet metal. Two
copper tubes are attached with the top of the annular space for PCM supply in the box and to
maintain the overflow. Another tube is attached in the bottom of the annular space to discharge
the PCM if necessary. Figure 3 shows the schematic diagram of the experimental set-up and
Figure 4 shows details circuitry of the setup. The modified PCM based refrigerator has a single

4. International Journal of Recent advances in Mechanical Engineering (IJMECH) Vol.3, No.1, February 2014
46
evaporator cabinet with a single door. The followings are the major technical specifications of the
refrigerator.
i) Cabinet : Internal volume, 0.03 m3
ii) Evaporator : Mode of heat transfer - Free convection, Linear length of the coil
/tube: 12.2 m, Internal and external diameter of the tube : 0.0762 m
and 0.0772 m respectively, Material of the coil/tube : Copper tube
iii) Condenser : Mode of heat transfer - Free convection, Linear length of the coil
/Tube: 5.8 m, Internal and external diameter of the tube : 0.003 and
0.004 m respectively, Material of the coil/tube: Steel and wire tube
iv) Compressor : Hermetic reciprocating compressor, HITACHI FL 1052- SK, 13 FL
220-240V, 50Hz
v) Expansion device : Capillary tube (Internal diameter 1 mm)
vi) On/off control and self defrost
vii) Refrigerant : 1,1,1,2-Tetrafluoroethane (R-134a)
Temperatures at various locations (compressor, condenser, evaporator and cabinet) are measured
with K-type (copper–constantan) thermocouples having 0.0005 m diameter as shown in Figure 4.
Three thermocouples are also positioned at the bottom, middle and the top of the PCM in the left
face of the cabinet to measure the temperatures of PCM. Two pressure transducers are used to
measure the evaporation and condensation pressures at the inlet and outlet of the compressor.
Another pressure transducer is placed at the inlet of the evaporator to measure the pressure drop
in the evaporator section. Four pressure gauges are used to cross check the pressure
measurements of the pressure transducer and the deviations have been found within ± 0.03 kg
/cm2
. The location of all of the pressure transducers and pressure gauges are shown in Figure 4.
Figure 1. The arrangement of the PCM based evaporator
Fig. 1(c) Evaporator
box inserted into
the PCM box
Fig. 1(a) Evaporator
cabinet with coil
Fig. 1(b) Empty PCM
Box
PCM direct contact
with the evaporator coil
and cabinet box
PCM inlet
Fig. 1(d) Shape of solid
PCM after phase change
(Liquid to solid)
PCM overflow

5. International Journal of Recent advances in Mechanical Engineering (IJMECH) Vol.3, No.1, February 2014
47
Figure 2. Front View of the evaporator cabinet with PCM box
Figure 3. Schematic diagram of the Experimental set-up
Heater
PC
Thermocouple
Compressor
Condenser
Evaporator Coil
Capillary tube
Cabinet
Annular space
for PCM
Data acquisition
system

6. International Journal of Recent advances in Mechanical Engineering (IJMECH) Vol.3, No.1, February 2014
48
Figure 4. Location of pressure transducer, pressure gauge and thermocouple
A heater is used in the cabinet to do experiments at different thermal loads. The heater is located
at the bottom of the cabinet box, which is linked with a variable voltage transformer (variac) to
control the supply voltage for required thermal load variation into the cabinet. A K-type
thermocouple is used for the measurement of the air temperature within the cabinet, which is
located at the center of the cabinet space. A thermostat is used to drive the compressor cycling;
the thermocouple of the thermostat is located at the centre of the cabinet. The experimental set-up
is equipped with a data acquisition system linked to a personal computer, which allows a high
sampling rate and the monitoring of all the measurements made by means of the thermocouples.
The experiments have been carried out in a room where the temperature and humidity are
maintained constant with the aid of air conditioner. All the data have been collected from the data
acquisition system after ensuring the steady state condition of the refrigerator. To obtain the
steady state condition the system is allowed to run for several minutes (about 70 minutes).
Experiments were carried out under four different thermal loads like 0, 5, 10 and 20 watt with
two different PCMs as shown in table-2.
Table 2. List of phase change material (PCM) used in this experiment
PCMs Melting temperature
( MT ) ( 0
C )
Latent heat of fusion
(kJ/kg)
Distilled Water (H2O) 0 333
Eutectic Solutions
(90% H2O + 10% NaCl), (%wt.)
-5 289

7. International Journal of Recent advances in Mechanical Engineering (IJMECH) Vol.3, No.1, February 2014
49
3. EXPERIMENTAL RESULTS & DISCUSSIONS
Figure 5 shows the effect of PCM on average air temperature inside the cabin at no load condition
which shows the average temperature fluctuation for a specific time is significantly reduced for
the system with PCM in respect to without PCM.
The compressor on-off mode is triggered by the thermostat which is located in the evaporator
compartment .The thermostat setting point has been adjusted so that it starts the compressor at -
3.90
C and stops at -50
C. This adjustment is to keep the evaporator cabinet temperature around -
50
C. In case of without PCM, during compressor off mode the cabinet temperature rises quickly
due to the heat inlet by the door opening and intake heat from the surroundings due to ambient
conditions. As a result the thermostat triggers the compressor in on mode quickly. On the other
hand when PCM is used this excessive heat is absorbed by PCM due to its phase change nature
(solid to liquid) which does not allow the compartment temperature rise quickly. A low enough
temperature near to the desired point inside the cabinet is maintained during the whole melting
period of PCM and the compressor is not triggered in on mode quickly by the thermostat. As a
result a prolonged off mode of compressor is obtained. This longer off mode of compressor
ultimately reduces the number of on-off cycle significantly which ultimately reduces temperature
fluctuation inside the evaporator cabinet for a certain period of time.
Figure 6 shows a comparison between two PCM, which is better for reduction of temperature
fluctuation inside the cabin at no load condition. From figure 4 it is clearly identify that The
reduction of the temperature fluctuation inside the cabin at the experimental setting temperature
of the evaporator chamber is higher for eutectic solution than water. A PCM gives better
performance for a house hold refrigerator if the melting point of the PCM is equal or greater than
the setting temperature of the evaporator chamber and if it has high latent heat of vaporization.
Between the two PCMs used in this work, Eutectic solution shows higher reduction of
temperature fluctuation within a certain period of time than water because of its better phase
change tendency. The melting point of Eutectic solution is -50
C and setting temperature of the
evaporator chamber is also -50
C. As a result Eutectic solution has a better phase change tendency.
0 8 16 24 32 40 48 56 64 72 80 88 96 104 112 120
-6.4
-6.0
-5.6
-5.2
-4.8
-4.4
-4.0
-3.6
-3.2
-2.8
-2.4
AverageairTemperatureinsidetheCabin(
0
C)
Time (min)
Without PCM
Eutectic solution (MT
= -5
0
C, Q=4.25 L)
Load = 0W
Q = 4.25L
Figure 5. The effect of PCM on average air temperature inside the cabin (Load = 0W)

8. International Journal of Recent advances in Mechanical Engineering (IJMECH) Vol.3, No.1, February 2014
50
0 8 16 24 32 40 48 56 64 72 80 88 96 104 112 120
-6.4
-6.0
-5.6
-5.2
-4.8
-4.4
-4.0
-3.6
-3.2
-2.8
-2.4
AverageairTemperatureinsidetheCabin(
0
C)
Time (min)
Without PCM
Water (MT
= 0
0
C, Q=4.25 L)
Eutectic solution (MT
= -5
0
C, Q=4.25 L)
Load = 0W
Q = 4.25L
Figure 6. The effect of PCM on average air temperature between two PCM inside the cabin at no load
condition
Though the water has higher latent heat of vaporization, it shows lesser reduction of temperature
fluctuation than other PCMs within a certain period of time because of its poor phase change
tendency for the -50
C setting temperature of the cabinet. Actually due to its 00
C melting
temperature it does not participate in the phase change process.
0 8 16 24 32 40 48 56 64 72 80 88 96 104 112 120
-6.4
-6.0
-5.6
-5.2
-4.8
-4.4
-4.0
-3.6
-3.2
-2.8
Time (min)
AverageairTemperatureinsidetheCabin(
0
C)
Without PCM
Water (MT
= 0
0
C, Q=4.25 L)
Eutectic solution (MT
= -5
0
C, Q=4.25 L)
Load = 05W
Q = 4.25L
Figure 7. The effect of PCM on average air temperature inside the cabin (Load = 05W)

9. International Journal of Recent advances in Mechanical Engineering (IJMECH) Vol.3, No.1, February 2014
51
0 8 16 24 32 40 48 56 64 72 80 88 96 104 112 120
-6.4
-6.0
-5.6
-5.2
-4.8
-4.4
-4.0
-3.6
-3.2
-2.8
Time (min)
AverageairTemperatureinsidetheCabin(
0
C)
Without PCM
Water (MT
= 0
0
C, Q=4.25 L)
Eutectic solution (MT
= -5
0
C, Q=4.25 L)
Load = 10W
Q = 4.25L
Figure 8. The effect of PCM on average air temperature inside the cabin (Load = 10W)
Figures 5-8 shows that the effect of thermal load on the performance of PCM inside the cabin
temperature and from this figure it is clearly concluded that if the thermal load is increased then
the PCM performance is decreased. So it is obviously suggest that at higher thermal load the
PCM effect is not so significant. At high thermal load system with PCMs and without PCM show
higher number of on-off cycle i.e. higher temperature fluctuation than that at low thermal load, as
the cabinet temperature quickly rises during the off mode of compressor. In case of PCM, at high
thermal load the rate of energy extracted by the PCM from the cabinet is not sufficient to provide
the cooling capacity needed to maintain the desired temperature of the cabinet long. That’s why
the thermostat triggers the compressor in on mode quickly. This reason shortens the off mode of
compressor and ultimately increases the number of on-off cycle of compressor which increases
the temperature fluctuation inside the cabinet, within a certain period of time.
CONCLUSIONS
Experimental tests have been carried out to investigate the temperature fluctuation inside the
evaporator cabin a household refrigerator using two different phase change materials at different
thermal loads. The following conclusions have been drawn from these experimental tests:
i) Use of PCM in a household refrigerator decreases the fluctuation of the cabinet temperature.
ii) The reduction of temperature fluctuation between two PCM, Eutectic solution is higher than
water.
iii) At higher thermal load this effect is not so significant.
This reduction of temperature fluctuation ultimately improves the food preservation quality of the
refrigerator

10. International Journal of Recent advances in Mechanical Engineering (IJMECH) Vol.3, No.1, February 2014
52
REFERENCES
[1] Blond, G., M. Le Meste, (2004) “Principles of frozen storage”, In: Hui, Y.E., Cornillon, P., Legaretta,
I.G., Lim, M.H., Murrell, K.D., Nip, W. (Eds.), Handbook of Frozen Foods.Marcel Dekker, New
York. pp. 25-53.
[2] Canet, W., (1989) “Quality and stability of frozen vegetables”, In: Thorne, S. (Ed.), Developments in
Food Preservation, Elsevier, London, pp. 1–50.
[3] Alvarez, M.D., W. Canet, (1998) “Effect of temperature fluctuations during frozen storage on the
quality of potato tissue (cv. Monalisa) Zeitschrift Fur Lebensmittel-Untersuchung Und Forschung A-
Food Research and Technology 206, pp 52–57
[4] Sousa, M.B., W. Canet, M.D. Alvarez, M.E. Tortosa, (2005) “The effect of the pre treatments and the
long and short-term frozen storage on the quality of raspberry (cv. Heritage)”,European Food
Research and Technology 221, pp 132–144.
[5] Flores, A.A., H.D. Goff, (1999) “Re-crystallization in ice cream after constant and cycling
temperature storage conditions as affected by stabilizers” J. of Dairy Science Vol. 82, No. 7, pp
1408–1415. DOI: 10.3168/jds.S0022-0302(99)75367-1
[6] Donhowe, D.P., R.W. Hartel, (1996) “ Recrystallization of ice during bulk storage of ice cream”, Int.
Dairy Journal Vol. 6, No. (11-12), pp 1209-1221. DOI: 10.1016/S0958-6946(96)00030-1
[7] Phimolsiripol, Y., U. Siripatrawan, V. Tulyathan, D.J. Cleland, (2008) “Effects of freezing and
temperature fluctuations during frozen storage on frozen dough and bread quality” J. of Food
Engineering, Vol. 84, No.1 pp 48-56. DOI: 10.1016/j.jfoodeng.2007.04.016
[8] Gormley, R., T. Walshe, K. Hussey, F. Butler, (2002) “The effect of fluctuating vs. constant
frozen storage temperature regimes on some quality parameters of selected food products”,
Lebensm.-Wiss. Technol. 35, pp 190-200.
[9] Maltini E., G. Cortella, M. Stecchini, M. Deltorre, P. Pittia, M. Spaziani, G. Mansutti, (2004)
“Design and Performances of a Constant Temperature Compartment for Domestic Refrigerator”
International Congress on Engineering and Food, Montpellier.
[10] Zalba B., J.M. Marin, L.F. Cabeza, H. Mehling, (2003) “Review on thermal energy storage with
phase change: materials, heat transfer analysis and applications”, Appl. Therm. Eng. Vol. 23, No. 3,
pp 251–283. DOI: 10.1016/S1359-4311(02)00192-8
[11] Subramaniam, P., C. Tulapurkar, R. Thiyagarajan, G. Thangamani, (2010) “Phase change materials
for domestic refrigerators to improve food quality and prolong compressor off time”, Int.
Refrigeration and Air Conditioning Conference at Purdue.
[12] Marques C., G. Davies, G. Maidment, J.A. Evans, I. Wood, (2010) “Application of phase change
materials to domestic refrigerators”, IIR Proceedings Series 'Refrigeration Science and Technology',
2010/5: 167-175.Copyright © 2010 International Institute of Refrigeration, 9th International
Conference on Phase-Change Materials and Slurries for Refrigeration and Air Conditioning 29
September - 1 October, Sofia, Bulgaria.
[13] Azzouz, K., D. Leducq, J. Guilpart, D. Gobin, (2005) “Improving the energy efficiency of a vapor
compression system using a phase change material. In: Proceedings 2ndConference on Phase Change
Material & Slurry”, Yverdon les Bains, Switzerland.
[14] Azzouz, K., D. Leducq and D. Gobin, (2009) “Enhancing the performance of household refrigerators
with latent heat storage: an experimental investigation”, Int. J. of Ref., Vol. 32,No.7, pp 1634-1644.
DOI : 10.1016/j.ijrefrig.2009.03.012
[15] Gin, B., M.M. Farid, P.K. Bansal, (2010b) “Effect of door opening and defrost cycle on a freezer with
phase change panels”, Energy Conservation and Management, Vol. 51, No. 12, pp 2698- 2706. DOI:
10.1016/j.enconman.2010.06.005
[16] Gin, B., M.M. Farid, (2010a) “The use of PCM panels to improve storage condition of frozen food”,
J. of Food Engineering, Vol. 100, No. 2, pp 372-376. DOI: 10.1016/j.jfoodeng.2010.04.016