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International Journal for Research in Engineering Application & Management (IJREAM)
ISSN : 2454-9150 Vol-04, Issue-07, Oct 2018
45 | IJREAMV04I0743005 DOI : 10.18231/2454-9150.2018.0894 © 2018, IJREAM All Rights Reserved.
A Review on Change in Properties of Phase Change
Materials (PCM) on Incorporating Additives
Vraj Mundra, Student-IV year, Medi-Caps Institute of Technology and Management, Indore,
India, [email protected]
Sourabh Mahajan, Student-IV year, Medi-Caps Institute of Technology and Management, Indore,
India, [email protected]
Bhupendra Singh Sikarwar, Assistant Professor, Medi-Caps University, Indore, India
Abstract: Latent heat energy storage and exchange system is emerging as an efficient alternative of storing extra
thermal energy for low consumption and slow energy delivery system. One of the challenges for latent heat storage
systems is the proper selection of the phase change materials (PCMs) for the targeted applications. The Phase change
materials in their native state display primitive heat storage and transition with discreet phase change properties,
melting and phase separation properties. To overcome these properties, doping or enhancement of the PCM is done,
quiet often which they differ is by the nature, structure or the fabrication of the composite displaying a myriad of
properties and their variation with change in additive’s structural matrix inside the composite, material of the additive
and their concentration inside the PCM. Furthermore, the nature of the bulk of PCM, display relatively distinct
properties as they may be organic or inorganic. This paper is a review based on the contemporary work done on
organic and inorganic PCM, their additives and effects of additives on the thermodynamic and phase change properties
of the composites, and gives an insight into potential uses and classification of the PCMs according to their properties
and ease of incorporation for industrial and domestic applications.
Keywords: PCM, Paraffin wax, embedded graphite, expanded graphite, Inorganic PCM, Metallic foam.
I. INTRODUCTION
The electrical/electronic goods are an integral part and
components in one‟s working life now-a-days. Abrupt rise
in the standard of living and the expansion of the
boundaries of what defines human comfort and luxury have
become necessities and this has been aided by rise in living
comforts, the affordability of electronics and rapid
industrialization. Therefore, the research is primarily
focused on miniaturizing the electronic components whilst
maintaining the computing power and efficiency of the
previous generation configurations of the system.
As of today, thermal management is the foremost concern
in developing and designing of new systems. Temperature
has been identified as the key factor in the performance and 1reliable operation of the electronic system. The traditional
methods of cooling, namely natural and forced convection
are no longer seen as sufficient alternatives for heat
exchange and subsequent cooling of high-performance
electronics. Alongside, PCM‟s have been widely
experimented and researched upon in civil engineering and
energy management domain, primarily as a backup latent
energy storage medium for smoothing out energy demand
fluctuations as well as acting as a passive heat/energy
release media in domestic heating/cooling applications.
PCM‟s have been also introduced as the cooling enhancer
in lithium ion batteries in electric vehicles and power
consuming battery operating devices.
The widespread potential uses and applications however are
not assisted or followed by a parallel rise in scientific
literature and research over the generalized industrial
potential of PCM and the effect of additives on their
properties, subsequent usage as well as their domain of
usability and fabrication. The cited works have been
extremely useful yet a bit myopic about the larger scope of
PCM in the widespread product design engineering and
industrial/civic application. Our work aims to comprehend
and distill the available works and findings of the research
work currently in progress as well as the past and provide a
brief and concise insight into the properties, fabrication as
well as the potential scope and spectrum of applications the
PCM can be put into practice.
A survey conducted by US air force noticed that the
temperature related failure in electronics exceeded in the
excess of 55% (E.M. Alawadhi and C.H. Amon [32]).
Manufacturing industry in communication systems expect a
reliability percentage of 99.99%, also called as 5 9‟s
International Journal for Research in Engineering Application & Management (IJREAM)
ISSN : 2454-9150 Vol-04, Issue-07, Oct 2018
46 | IJREAMV04I0743005 DOI : 10.18231/2454-9150.2018.0894 © 2018, IJREAM All Rights Reserved.
principle. Which translated to roughly 5 minutes of total
down time in any year. These high expectations ensure that
the conventional cooling methods are inadequate for the job
demanded from them. It has been found that a 1 °C
decrement in a localized temperature may lower its failure
rate percentage by as much as 4% and about 10–20 °C
increment in temperature can increase its failure rate by
100% ( S.F.Hosseinizadeh et al. [33]).”
The cooling methods used are mainly active and passive in
nature. The active cooling designs work by direct contact,
like a metal surface with many fins incorporated. This heat
transfer is obtained through free or forced convection,
liquid cooling or any combinations of them possible in
practice. In forced convection, heat sinks‟ thermal
performance is increased by uplifting overall heat transfer
coefficient, usually by adding a fan to the system. Fans
improve the transfer of thermal energy from the heat sink to
the surrounding air by moving cooler ambient air between
the fins, the major disadvantage of the fan system being is
noise, life, size and vibration. Wherever there is some
improper functioning of fan, like imbalance and rotational
friction, the system fails to operate for longer duration due
to generation of more heat and vibrations. Hence in recent
years, passive cooling is gaining property in passive cooling
applications. PCM exhibit properties of high latent energy
of fusion and relatively small amount of volume change
during energy absorption. This demonstrates that high
amount of energy can be reliably stored in PCM during its
phase change battery, not unlike a slow charging
conventional battery.
The physical and thermodynamic properties of PCM with
additives, mixed/impregnated/expanded (Organic) or other
methods (Inorganic) have been studied and discussed about
in this paper. The common properties mentioned in all our
citations have valuable insights into the thermal
conductivity, thermal storage, latent heat, temperature
distribution, reliability, effect of temperature distribution on
thermal conductivity.
For ease of comprehension and reference the PCM are
classified on some discreet divisions with insignificant
overlap due to the nature of experiments carried out but
mainly divided on nature, additives and melting points of
the PCM composites. The studied PCM in this paper are
classified by nature additives and melting points.
Organic composites:
1) Paraffin:
i) Expanded graphite
ii) Embedded graphite nanofibers
iii) Porous graphite matrix
iv) High density Poly ethylene composite
v) Carbon foam and contrast with isolated
carbon foam
vi) Carbon fiber
vii) RT44HC paraffin with expanded graphite
viii) Embedded herringbone style graphite
nanofibers
2) 1-Octadecanol
i) Graphene
ii) Graphene sheets
3) Poly-ethylene Glycol
i) SiO2 composite
ii) Graphite-nano-plates/Poly-methyl
Methacrylate composite
4) MA-PA-SA
i) Expanded graphite
Inorganic composites:
1) Pristine silver epoxy, hybrid graphene FLG- Silver
epoxy
2) LiNO3-KCl, LiNO3-NaNO3, LiNO3-NaCl
impregnated with expanded graphite
3) PCM44 {Mg (NO3)26H2O–MgCl26H2O–NH4NO3}
with carbon fiber
4) NaNO3 in copper.
Melting Points (Binary classification):
1) High temperature PCM (melting points above 2000C )
2) Low temperature PCM (melting points below 2000C)
The objective of this paper is to recollect and encapsulate
data and conclusions from various sources and researches
to make a comprehensible and self-contained source of
information regarding the properties, fabrication and
potential applications of PCM in industry.
II. CONTEMPORARY STUDIES ON PHASE
CHANGE MATERIALS
1. ORGANIC MATERIALS
1.1 Thermal conductivity
H. Yin et al. [1] studied the effect on thermal conductivity
of paraffin by adding expanded graphite in it. It was known
that thermal conductivity of paraffin with 0% of expanded
graphite is 0.2697W/mK, but during experiments it was
seen that thermal conductivity of composite increases on
adding 6.25% of graphite in paraffin which is 4.676W/mK
& on further inclusion of graphite thermal conductivity
observes downward trend i.e. it decreases to 1.795W/mK at
90.9% of graphite in PCM. Therefore, there is an optimized
range of doping of expanded graphite in paraffin.
C. Lin et al. [2] conducted experiment on LiFePO4 battery
of size (length*breadth*height) 100*32*180 (mm) to check
the rise in thermal conductivity on adding expanded
graphite in paraffin. It was found that there is increase in
thermal conductivity of composite to 24 times as that of
pure paraffin as shown in Table I.
Table I: Thermal properties of Paraffin and Paraffin EG composite
[2]
International Journal for Research in Engineering Application & Management (IJREAM)
ISSN : 2454-9150 Vol-04, Issue-07, Oct 2018
47 | IJREAMV04I0743005 DOI : 10.18231/2454-9150.2018.0894 © 2018, IJREAM All Rights Reserved.
Paraffin Paraffin and
expanded graphite
composite
Thermal conductivity
(W/mK)
0.16 3.95
Latent heat (kJ/kg) 174.4 132.6
Phase change
temperature oC
223.9-27.1 21.6-25.5
F. Yavari et al. [3] in their study studied the effect of
adding nano structured graphene in 1 – Octadecanol. It was
found that on insertion of 4% of graphene in 1-Octadecanol
there is 2.5 times rise in thermal conductivity of composite
from (0.38W/mK to 0.91W/mK). This increase in thermal
conductivity can be considered due to high thermal
conductivity network of filler material (graphene) and may
be large aspect ratio.
W. Wang et al. [4] conducted the study in which they form
a composite by blending polyethylene glycol, β -Aluminum
nitride powder and silica gel. Due to doping in pure PCM
there is rise in thermal conductivity of PCM. It is also seen
that as mass ratio of β-Aluminum Nitride increases, there is
increase in value of thermal conductivity which increase
from 0.3847 to 0.7661W/mK.
G. Xin et al. [6]in his work firstly forms a defect free
graphene then doped this defect free graphene into phase
change material. Fig. 1 shows the effect of mass loading of
GSs on thermal conductivity of pristine graphene/PCC
(PGPCC). It is known that measured thermal conductivity
of pure PCM is 0.22W/mK at ambient temperature. It is
seen that at loading from 0% to 10% Pristine GS there is
increase of thermal conductivity from 0.27 to 0.55W/mK.
Further TCE of PGSPCC is found to be 1.5 at 10% weight
of PGS.
Fig 1: Thermal conductivity and thermal conductivity enhancement
of pristine graphene/PCC (PGPCC)
at various mass loading fraction of GSs [6]
X. Yang et al. [7] performs an experiment in which they
measure the effect of expanded graphite on myristic acid–
palmitic-acid–stearic acid. Proportion of myristic acid–
palmitic-acid–stearic acid and EG was kept 13:1. On
comparison of thermal conductivities it was observed that
thermal conductivity of MA–PA–SA/EG composite PCM is
10.04 time higher than that of pure PCM.
W. Wang et al. [8] in his study forms a composite of
polyethylene glycol/silicon dioxide and studied its effect on
thermal properties. It was found that in table that with
increase in percentage of SiO2 there is increase in thermal
conductivity which reaches to 0.5124 W/mK but due to
constraint of heat storage mass percentage is optimized at
20% at which thermal conductivity is 0.3615 W/mK.
Table II: Thermal conductivity of the composite PEG (10,000)/SiO2 [8]
Samples Weight
percentage of
SiO2
Conductivity
(W/mK)
Increases
Percentage
1 0 0.2985 0
2 20 0.3615 21.0
3 30 0.4126 38.2
4 40 0.4783 60.2
5 50 0.5124 71.7
A. Trigui and M. Karkri [10] in order to determine apparent
thermal conductivity of liquid and solid of composite,
between up and down side of composite temperature
difference was applied until equilibrium condition. They
prepared two composite paraffin/epoxy resin/copper tube
(1) and paraffin/epoxy resin/brass tube (2). It was observed
that thermal conductivity of (1) sample without PCM was
0.270W/mK which increases to 0.280W/mK on in liquid
state on adding PCM. While thermal conductivity of sample
(2) without PCM was 0.214W/mK which increases to
0.218W/mK on adding PCM in liquid state.
A. Sari [13] in work forms a form stable composite
paraffin/high density polyethylene (HDPE). He used two
types of paraffin (P1 and P2) having different melting
temperature of 42 – 44oC and 56 - 58
oC respectively. In
order to increase thermal conductivity of composite, 3% of
expanded graphite is added in composite which changes
percentage of paraffin and HDPE to 74.7 and 22.3 w/w %
respectively. As result of inclusion of EG it is observed that
there is increase in thermal conductivity of P1/HDPE and
P2/HDPE by 14 and 24% respectively.
Z. Ling et al. [16] conducted the investigation in which he
forms a composite of RT44HC/expanded graphite (EG) to
check the change in properties of pure PCM on addition of
EG. It is seen that thermal conductivity at 35% of EG is
nearly 30 times more than that of 25% mass fraction of EG.
Further it is seen that packing density has great influence
over thermal conductivity. It is seen that with increase in
packing density there is increase in thermal conductivity. At
density of 300 kg/m3 thermal conductivity of 25% EG was
4.3W/mK which increase to 10.7W/mK at density of 900
kg/m3.
1.2 Latent Heat
C. Lin et al. [2] conducted the experiment in which they
investigate the effect of using paraffin with expanded
International Journal for Research in Engineering Application & Management (IJREAM)
ISSN : 2454-9150 Vol-04, Issue-07, Oct 2018
48 | IJREAMV04I0743005 DOI : 10.18231/2454-9150.2018.0894 © 2018, IJREAM All Rights Reserved.
graphite in LiFePO4 battery. It was found that latent heat of
composite decrease to 132.6 kJ/kg as compared to that of
pure PCM which was 174.4kJ/kg. This decrease is due to
the impregnation of graphite in PCM. The Latent heat of
the composite is shown in Table I.
W. Wang et al. [4] in their experiment evaluated the change
in latent heat of polyethylene glycol, β –Aluminum nitride
powder and silica gel composite. In Fig. 2 two pointed
peaks were observed indicating solidification point and
melting point. Solidification point during cooling and
melting point during the
Fig 2: DSC Curve of the PEG/SiO2/ β –AlN composite PCM [4].
heat was 44.81 o
C and 60.93 o
C respectively, whereas latent
heat of solidification and melting process was 117.6 kJ/kg
and 137.7 kJ/kg respectively. Further the author calculated
latent heat, solidification and melting point of PCM at
various percentage of β – Aluminum Nitride and results are
shown in Table III.
From Table III it is seen that on increasing the percentage
of β-Aluminum Nitride there is a decrease in the value of
latent heat with a very insignificant change on crystallizing
and melting temperature respectively.
Table III: Thermal activities of the PEG/SiO2/β-AlN composite PCMs
[4]
AIN% Hm
(kJ/kg)
Tm (oC) Tc (
oC) Hc
(kJ/kg)
1 161.4 60.41 45.13 132.9
5 154.6 62.32 43.96 129.8
10 152.8 58.59 45.04 128.7
15 137.7 60.93 44.81 117.6
20 129.5 61.18 42.39 106.8
X. Yang et al. [7]in his experiment found that the melting
and freezing temperature of myristic acid–palmitic acid–
stearic acid and EG composite are 41.64oC and 42.99
oC
respectively and the melting and freezing latent heat to be
151.4 kJ/kg and 153.5 kJ/kg respectively.
Table IV: Comparison of thermal properties of the prepared
composite PCM with that of some composite PCMs in literatures. [7]
Composite
PCM
Meltin-g
point
(oC)
Freezin-g
point (oC)
Latent
heat
(kJ/kg)
Reference-s
Capric–myristic
acid (55
wt%)/expanded
perlite
21.70 20.70 85.40 A.
Karaipekli
and A. Sari
[25]
Capric–lauric
acid (66
wt%)/diatomite
16.74 – 66.81 M. Li et al.
[26]
Lauric acid (33.3
wt%)/activated
carbon
44.07 42.83 65.14 Z. Chen et
al. [27]
Stearic acid (47.5
wt%)/activated
montmorillonite
59.9 55.1 84.4 Y. Wang et
al. [28]
Stearic acid
(83%)/expanded
graphite
53.12 54.28 155.50 G. Fang et
al. [29]
Palmitic acid
(80%)/expanded
graphite
60.88 60.81 148.36 A. Sari and
A.
Karaipekli
[30]
Myristic–
palmitic–stearic
acid (92.86
wt%)/expanded
graphite
41.64 42.99 153.5 X. Yang et
al. [7]
G. Xin et al. [6] studied the influence on phase change
enthalpy of 1 – octadecanol on adding GS. It is seen that
phase change enthalpy of 1-octadecanol decrease on
addition of GS. There was minor reduction in enthalpy 225-
222kJ/kg at 55 oC of GSs loading, while at 10% reduction
in enthalpy of PGPCC and AGPCC reaches to 199kJ/kg
and 195kJ/kg respectively. This reduction is observed
because now volume of PCM decreases as some place of
PCM is occupied by GS which in turn do not contribute to
phase change.
Further it was seen TCE of 13.33 o
C is achieved at 15% of
loading fraction in PGPCC but it is still less than that of
AGPCC.
W. Wang et al. [8] checked the influence of SiO2 over
polyethylene glycol (PCM) and found that latent heat of
polyethylene glycol at temperature 61.8 o
C is 187.3 kJ/kg
which was slightly higher than that of composite which is
162.9 kJ/kg at temperature 61.61 oC, this indicates that there
is no reaction between PCM and silicon dioxide.
X. Fang et al. [11] compared predicted and measured latent
heat of fusion of eicosane – graphite nanofiber composite at
various loading of GNP in figure 3. It is known that latent
heat of fusion is approximately inversely proportional to the
loading. There is decrease latent heat of fusion in composite
as compared to that of pure PCM by 0.5%, 1.7%, 5.4% and
16% on loading of 1%, 2%, 5% and 10% respectively. At
International Journal for Research in Engineering Application & Management (IJREAM)
ISSN : 2454-9150 Vol-04, Issue-07, Oct 2018
49 | IJREAMV04I0743005 DOI : 10.18231/2454-9150.2018.0894 © 2018, IJREAM All Rights Reserved.
loading of 10% composite has the thermal conductivity of
2W/mK and latent of fusion to be 220kJ/Kg.
Fig 3: Comparison of the measured and predicated latent heat of
fusion of the eicosane-based composite PCMs with various loadings of
the GNPs [11].
A.Sari [13] in his experiment found that on increasing
the percentage of paraffin or decrease in the percentage of
HDPE, there is an increase in the latent heat. At 50:50 ratio
paraffin and HDPE latent heat was 95.7 kJ/kg which get
rise to 192.8 at ratio of 100:0 of paraffin and HDPE. But on
decrease the percentage of HDPE there is decrease in
strength of PCM there percentage is optimized at 77% of
paraffin with 33% HDPE. At this ratio latent heat of
P1/HDPE and P2/HDPE is takes as 146.7 o
C and 162.2 o
C
respectively.
Z. Ling et al. [16] in his experiment on investigation found
that the phase change enthalpy of RT44HC/expanded
graphite (EG) composite with 25% EG is 168.1 kJ/kg while
on increase percentage of EG to 35% phase change
enthalpy decrease to 152.5 kJ/kg.
L. Zhang et al. [17] in their study found that at mass
fraction of 0% of GNP in form stable polyethylene
glycol/polymethyl methacrylate, theoretical latent heat of
melting and freezing was 125kJ/kg and 114kJ/kg
respectively which decrease to approximately to 117kJ/kg
and 113kJ/kg at mass fraction of 8% respectively. Same
was observed as that were observed with another
composites.
R. J. Warzoha et al. [18] investigated the relation between
latent heat of fusion of HGNF/PCM and peak melt
temperature. It is seen in Table V that with increase in
percentage on HGNF in paraffin there is decrease in latent
heat of fusion. Latent heat of fusion of pure PCM is 271.6
kJ/kg which decrease to 242.7kJ/kg at 11.4% of HGNF.
Further with increase in HGNF there is increase in peak
melt temperature from 327.75 K to 333.65 K at 0% to
11.4% respectively.
Table V: Peak melt temperature and latent heat of fusion values for
HGNF/PCM nanocomposites [18].
Sample Peak melt
temperature (K)
Latent heat of
fusion (kJ/kg)
IGI 1230A 327.75 271.6
2.8% HGNF 330.55 252.9
5.8% H-GNF 330.15 251.3
8.5% H-GNF 330.35 250.6
11.4% H-GNF
333.65 242.7
333.65 242.7 242.7
Z. Zhang et al. [19] in his experiment found that at paraffin
mass fraction of 92% latent heat of composite (paraffin and
expanded graphite) was 170.3 kJ/kg which was lower than
that of latent heat of pure paraffin which was 188.2 kJ/kg.
1.3 Temperature variation
H. Yin et al. [1] in his experiment investigated temperature
distribution of paraffin/expanded graphite curve over
different heat input. It is seen that the phase change of
composite PCM is reached in Line 4.
In Figure 4 at heat input 37.5W before that phase change
was not achieved. Further all curve follows same pattern
i.e. curve experience rise till power is supplied and after
that there is decrease when heat input is shutoff.
Fig 4: Temperature variation curves of composite PCM [1].
C. Lin et al. [2] in his experiment which he performed by
using expanded graphite and paraffin composite found that
phase change temperature of composite reduced to 21.6 –
25.5 oC which was 23.9 – 27.1
oC for pure PCM.
O. Sansui et al. [5] conducted an experiment in which they
impregnated GNF in paraffin. They evaluated a transient
temperature profile for various temperature profile. It was
observed that at constant mass/volume and power input,
there was change in heat flux due to change in aspect ratio
i.e. on supplying heat input of 500W at A.R. = 0.5 (q = 2.5
W/cm2), at A.R. = 1 (q = 5 W/cm
2) and at A.R. = 2 (q = 10
W/cm2). It was seen that solidification time of pure paraffin
at A.R. of 1 is 80 min which reduces to 69 min at A.R. of
0.5 and increase to 225 min at A.R. of 2. But when GNF is
embedded in PCM it is observed that solidification time at
International Journal for Research in Engineering Application & Management (IJREAM)
ISSN : 2454-9150 Vol-04, Issue-07, Oct 2018
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A.R. of 0.5 and 2 changes. At AR. Of 0.5 there is reduction
of A.R. to 56 min of pure PCM which is 19% while
reduction of solidification time of A.R. of 2 is 39 min
which is 78% of time of pure PCM.
G. Xin et al. [6]in his experiment evaluated the temperature
response of phase change composite of annealed graphite
and PCM during heating and cooling.
Fig 5 (a) shows temperature response of phase change
composite during heating. To measure transient temperature
response samples of AGPCC, PGPCC both with loading
fraction of 10% and pure PCM is created of circular shape
and put into cylindrical mold which was kept hot isothermal
plate at 105 o
C. When approaching Tm, phase change takes
places and temperature of surface remain stable. Time
required to attain the phase change of 1-Octadecanl was
found to be highest that is 135s and final surface
temperature was found maximum of AGPCC which was
101 oC.
Fig 5(a): Temperature response of PCCs during heating [6]
The beginning temperature of AGPCC was maximum; 101
oC, due to its maximum thermal conductivity. It is clearly
being seen that as the time increases there is a rapid
decrease in temperature of AGPCC as compared to other
two. From their respective plateau length, it was seen that
AGPCC can store higher thermal energy at increased rate
during phase change.
Fig 5 (b): Temperature response of PCCs during cooling [6]
W. Wang et al. [8] in their study found that at 60 o
C PEG
was solid but as the temperature increases to 64 o
C some
part of PCM starts to melt and at 68 o
C there is complete
change of PEG into liquid state.
In contrary to this even at 110 o
C, there was minuscule
amount of volume change in composite of PEG/SiO2
showing that it is in solid state.
„A. Babapoor et al. [15] has his study on change of
properties of paraffin on insertion of carbon fiber. Fig. 6
shows local temperature versus time for composite having
0.46% wt mass fraction of carbon fiber at constant rate of
heat dissipation (2W) and fiber length of 2 mm. It is
observed from the graph that on increasing radial location
there is a decrease in local temperature. Maximum
temperature reaches to 47 0C at 7mm of radial location.
Fig 6: Local temperatures versus time at constant rate of heat
dissipation (2 W) for a composite containing 0.46% wt. carbon fiber
and fiber length of 2 mm [15].
Fig. 7. Time variation of the simulator surface temperature
vs different mass ratios of carbon fiber (fiber length = 1
mm). It is observed that with increase in time there is
increase in temperature battery. It was seen that when
system is enclosed it has its maximum temperature rise as
compared to pure PCM and composite. Temperature curve
can be break down in three portions. First prior to melting
phase when time is less then 50min. In this portion
temperature rise is maximum because of high latent heat. In
second portion time is between 50 min and 150min. where
rise in temperature is at slower rate as phase change occurs.
And in the last portion composites reaches temperature
stability at time greater then 150min. It was observed that
composite with 0.46% mass fraction of carbon fiber is the
most efficacious among all composites.
International Journal for Research in Engineering Application & Management (IJREAM)
ISSN : 2454-9150 Vol-04, Issue-07, Oct 2018
51 | IJREAMV04I0743005 DOI : 10.18231/2454-9150.2018.0894 © 2018, IJREAM All Rights Reserved.
Fig 7: Time variation of the simulator surface temperature for
different mass ratios of carbon fiber (fiber length = 1 mm) where W1=
0, W2=0.32, W2=0.46, W3=0.56 and W4=0.69 are the mass ratio of
fiber [15].
1.4 Thermal Storage Performance
H. Yin et al. [1] studied the effect of expanded graphite on
the performance of paraffin. It was seen that time required
by pure paraffin to reach 66 o
C from 28.5 o
C is 1010s in
comparison to time for composite is only 350s which was
65.3% of pure PCM. Further time required for cooling of
the composite was 2620s which was 26.2 % lower than that
of pure paraffin.
W. Wang et al. [4] studied the change in thermal
performance of polyethylene glycol/ SiO2 – β AIN
composite. Fig. 8 shows the heat release and storage curve
of pure PCM and composite.
On investigation it was seen that PEG takes 577s to reach
80 oC from 28
oC in contrast to it time taken by composite is
265s to attain same temperature.
Further during solidification process, it was observed that
composite PCM crystallize rapidly as compared to that
PEG. It was seen that the composite takes 1225s to freeze
whereas time taken by PEG to freeze is 2720s.
Fig 8: Heat storage and release curves of PEG and PEG/SiO2/β-AlN
[4]
O. Sansui et al. [5] studied the effect on thermal
performance after the impregnation of GNF in paraffin. Fig
9 shows the relation between Stefan‟s number and time for
composite as well as pure PCM at power input of 4W/cm2
and 20 W/cm2. It is seen that at heat flux of 20W/cm
2 time
required for complete solidification of pure PCM is 52 min
which reduces to 20.5 min on addition of graphite nanofiber
in PCM which is approximately 60% reduction of
solidification time. It is very beneficial in electronic cooling
requires for more operating time, so that PCM can get
rejuvenate for next cycle.
Fig 9: St vs. time the 5.08 cm side length cubic TCU cube with paraffin
and GNF/paraffin [5].
While at a low heat flux of 4 W/ cm2 for pure PCM
solidification time was 27 min but when GNF is embedded
in PCM, it was noticed that there is not requirement of
solidification time because PCM‟s steady state is achieved
under melting time.
B. Wu and Y. m. Xing [9] perform the numerical study and
evaluated the temporal variation of heat transfer for carbon
foam‟s different porosities in organic PCM. On
investigation it was seen that the composite with porosity of
0.95% has heat transfer approximately 3 times greater than
that of heat transfer of pure PCM. It is well evident from
the graph that after some time graph experience negative
trend.
J. M. Marin et al. [12] studied the influence of graphite on
the properties of paraffin. Table VI shows the energy
storage and process time for the accumulator with and
without PCM. It is seen that time taken by system to reach
at zero heat exchange for PCM with graphite is 50% lower
that of pure PCM. Further effect of mixing of graphite in
PCM on energy stored is also very slight about 12% to 20%
reduction.
Table VI: Process time and energy stored for loading and unloading of
the accumulator for the PCM without and with a graphite matrix [12].
Type of
process
C
(m3/h)
Process
time (h)
RT-25
Process
time (h)
composite
Stored
energy
(kJ)
RT-25
Stored
energy
(kJ)
composite
Solidification 100 6.31 3.16 602 525
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Solidification 150 5.47 2.55 600 510.75
Melting 100 7.34 2.83 591 476
Melting 150 6.32 3.47 592 475
W. G. Alshaer et al. [14] studied the effect of the two
different carbon foams (CF-20 and KL1-250), multi wall
carbon nanotube on paraffin (RT-65).
Fig. 10. Temperature histories of thermocouples at power
of 30W of different TM modules. It is seen from the graph
8(a) that time taken to reach 60 o
C is approximately 450s
for pure CF-20 whereas for CF-20+RT65 and CF-
20+RT65/MWCNTs is about 600s. Further to reach 80 o
C
time required is 1100s for CF-20 while CF-20+RF65 and
CF-20+RT65/MWCNTs observed time lag of 800s and
1700s respectively.
Fig 10: Temperature histories of thermocouples of different TM
modules (power = 30 W) [14].
Fig. 11. Heater temperatures for different thermal
management modules at different uniform power levels. It
is seen from all curves that with an increase in power
supply of heater there is increase in temperature of heater.
But in all scenario, it was observed that CF-
20+RT65/MWCNTs perform better as compared to CF-20
and CF-20+RF65.
It is seen that that for KL1-250 power supplied was 58W
while for CF-20 was 18W but approximately same steady
state temperature heater temperature is reached. His study
implies that power carrying capacity of KL1-250 is more of
CF-20. When RT65/MWCNTs is doped in KL1-250 steady
state temperature is 1.2 o
C lower than that of KL1-250
while KL1-250+RF65 which can lead to increase in thermal
conductivity.
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Fig 11: Heater temperatures for different TM modules at different
uniform power levels [14].
Z. Zhang et al. [19] in their experiment studied the effect of
expanded graphite on thermal storage of paraffin. It is seen
that at 92% of mass fraction of graphite and time period of
123min, temperature remain constant at 68.5 o
C for
composite PCM in contrast to it at time period of 385min
temperature of pure paraffin was 66.8 o
C. This property of
the composite shows thermal conductivity of composite is
higher than that of pure paraffin.
1.5 Thermal Recycle Stability
G. Xin et al. [6] in their study of recycling stability of
composite of GS and organic PCM. Fig. 12 shows the
transient temperature response of PCC before and after
recycling. In order to check thermal stability transient
temperature responses of AGPCC has been compared (at
temperature of 2200 °C annealed GSs and with 10 wt. %
loading fractions) before and after melting-solidification
cycles. Phase change composite was melted till 105°C and
then cooled till 20°C continuously for 50 cycles. It was seen
that phase change enthalpy and thermal conductivity gives
excellent performance.
Fig 12: Transient temperature response of PCC before and after
recycling with temperature °C on y axis and time on x axis [6].
X. Yang et al. [7] studied the change on thermal properties
of myristic acid–palmitic acid–stearic acid and EG
composite after 500 and 1000 cycles. They found that after
500 cycle there is increase in 1.03°C in freezing
temperature which changes to 44.02°C while there is
decrease of 0.46°C in melting temperature which changes
to 41.18°C. Further they also observed change in latent heat
of freezing and melting which changes to 150.8 kJ/kg and
152.6kJ/kg, which is very slight. After 1000 cycle change
in solidification and melting temperature is 0.28°C and
0.48°C respectively, while that is latent heat of
solidification and melting is -1.32% and -1.62%
respectively.
1.6 Effect of temperature on thermal conductivity
G. Xin et al. [6] studied the impact on thermal conductivity
on change in temperature. Fig 13 shows relation between
annealed graphene/PCC (AGPCC) at 5 wt. % loading
fractions of GSs and various annealing temperatures.
It is found that with the anneal fraction of 5% thermal
conductivity increase from 0.7 W/mK to 1.32 W/mK with
temperature ranging between 1600 °C to 2200 °C. While at
this fraction increase in TCE from 2.18 W/mK to 5 W/mK.
This is due to elimination of lattice defect on Gs and of
oxygen functional group.
Fig 13: Thermal conductivity and thermal conductivity enhancement
factor of graphene-PCCs annealed graphene/PCC (AGPCC) at 5 wt
% loading fractions of GSs with various annealing temperatures [6].
X. Fang et al. [11] conducted the experiment in which they
added graphene nano platelets in organic PCM eicosane to
evaluated change in thermal conductivity as function of
temperature of composite as compared to that of pure PCM.
It is seen that at loading of 0%, 1% and 2% respectively
curves are nearly parallel to each other i.e. independence of
temperature but there is increase in thermal conductivity
with increase inn loading. At 10% loading a trough is
observed between 20-30oC having nadir at 25
oC. At 1%
loading value of thermal conductivity is approximately
2W/mK which was approximately 400 times higher than
that of pure eicosane. On comparison to thermal
conductivity of eicosane/CuO presented by Nabil and
Khodadadi much lesser even for 10% of composite than 1%
of eicosane/GnP composite.
Further they studied the change in thermal conductivity in
temperature range of 30 o
C to 35 o
C. It is observed from the
graph that there is minute increase in thermal conductivity
from 30 o
C to 31 o
C. But after that there is constant increase
in thermal conductivity at all loading. In few loadings there
is approximately 1.2W/mK increase in thermal conductivity
from 30 oC to 35
oC.
Z. Ling et al. [16] studied the temperature dependent
thermal conductivity of RT44HC/EG composite where
mass fraction of EG is 25wt%. It is seen that thermal
conductivity of composite increases up to 50-60% on
addition of EG to PCM. Further it is also observed that
thermal conductivity above 45 o
C and below 35 o
C is
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approximately same. But within phase change temperature
range there is there is nearly double rise in thermal
conductivity i.e. at 42 o
C thermal conductivity of composite
with density 700kg/m3 is 14.7W/mK which approximately
double of thermal conductivity at 30 oC which is 30W/mK.
R. J. Warzoha et al. [18] studied the temperature dependent
thermal conductivity HGNF and paraffin composite. Fig.
14. (a) shows the temperature-dependent thermal
conductivity of HGNF/PCM composites, (b) variance ratio
(ratio of solid and liquid thermal conductivity).
From the figure it is seen that the thermal conductivity in
liquid phase is lower than that of thermal conductivity in
solid phase. It is seen that thermal conductivity is
dependent on temperature
But it cannot be considered as strong function of
temperature.
Fig 14: Temperature-dependent thermal conductivity of HGNF/PCM
composites, (b) variance ratio (ratio of solid and liquid thermal
conductivity) [18].
It is seen from 14(a) there with increase in percentage of
inclusion of HGNF from 0 to 11.4% & there is increase in
value of k/k base paraffin solid from 1 to 1.8 for solid phase. In
liquid phase region there is decrease in thermal
conductivity of 11.4% HGNF to nearly 1.
Further on evaluating ratio of thermal conductivity in solid
phase to that in liquid phase it is seen that at 8.5% of HGNF
ratio is highest nearly 2.4.
2. INORGANIC PCM COMPOSITES:
2.1 Thermal conductivity
V. Goyal and A. A. Balandin [23] performed an experiment
to evaluate the thermal conductivity of pristine silver
epoxy, hybrid graphene-FLG-silver-epoxy composites. It is
seen in Fig 15 that at 0% of graphene volume fraction
thermal conductivity of composite was 1.67WmK but it
was observed that with increase in percentage of volume
fraction there was drastically rise in thermal conductivity.
Fig 15: Thermal conductivity of the pristine silver epoxy, hybrid
graphene-FLG-silver-epoxy composites, and the reference silver
epoxy-carbon black composites as a function of the volume fraction f
of the graphene-FLG nano-micro-filler [23].
Further they also evaluated thermal conductivity of hybrid
graphene-FLG-silver-epoxy composites as a function of
temperature. It is observed that temperature has
insignificant effect over thermal conductivity of silver
epoxy graphene composite which was very beneficial.
Further in range of temperature from 0-75 o
C with rise in
volume fraction of graphene there was increase in thermal
conductivity but remain constant with increase in
temperature.
Fig 16: Thermal conductivity of the hybrid graphene-FLG silver
epoxy composite as a function of temperature for 1%, 3%, and 5% of
the volume fraction of graphene-FLG filler loading. Note that the
thermal conductivity almost does not change in the examined range,
which is important for TIM applications [23].
L. Zhong et al. [21] performed an experiment to study
change in thermal conductivity of three binary molten salts
(LiNO3–KCl, LiNO3–NaNO3 and LiNO3–NaCl) on
impregnation of expanded graphite. It is known that thermal
conductivity of expanded graphite is 7.34 W/mK and that
of molten salts are usually around 1 W/mK. Therefore, in
order to increase the thermal conductivity of PCM, higher
thermal conductive material is added. It is seen in fig 17
that thermal conductivity of composite is increased to 5-6
times that of their respective pure form PCM.
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Fig 17: Thermal conductivity of the samples [21].
F. Frusteri et al. [22] performed an experiment to check the
influence of carbon fiber on the PCM 44 which is Mg
(NO3)26H2O–MgCl26H2O–NH4NO3. They observed the
enhancement of thermal conductivity at different length of
fiber. It is seen from the graph that thermal conductivity
increases with increase with increase in mass fraction of
carbon loading. Further it was also seen that thermal
conductivity of decrease with increase in size of carbon
fiber.
2.2 Phase change properties
L. Zhong et al. [21] performed an experiment to study the
influence of expanded graphite on LiNO3–KCl, LiNO3–
NaNO3 and LiNO3–NaCl. It is seen that melting
temperature of pure PCM is lower than that of composite
PCM (impregnated with expanded graphite). While other
properties such as latent heat of fusion, solidification
temperature and enthalpy of crystallization are higher for
pure PCM as compared to that of composite PCM. Further
all properties of LiNO3–KCl and its composites are lower
than that of LiNO3–NaCl and its composites.
2.3 Thermal energy system
Z. Li and Z. G. Wu [20] performed a numerical study to
study the thermal energy of NaNO3 in copper in steady
state an in unsteady state.
In steady state they found that total heat flux without
natural convection of pure PCM is 196 W/m2 which is very
less as compared to that of composite PCM. It was seen that
maximum heat flux is obtained at porosity of 0.90 and
30PPI which is 5656.9 W/m2 at 96.3 % mass fraction of
copper matrix struts. As compared to heat flux without
convection, heat flux in convection get significantly rise. It
was observed that heat flux of pure liquid PCM was 3793.0
W/m2
which increases to 11965 W/m2
at porosity of 0.90
and 5PPI with 78.9 mass fraction of copper matrix strut.
While in unsteady state it is seen that melting time of the
pure PCM is 739 s which get reduced to 29.9 – 38.7% and
20.6 – 29.0% with composite of porosity of 95 and 90%
respectively. Further melting time of composite with
porosity of 90% was 69-75% lower than that of composite
with porosity of 95%. The melting process is endothermic
process.
It was further seen that solidification time of pure PCM is
5406s which gets reduced to 213s with copper foam having
porosity of 0.90 and 30PPI. It was seen that total
solidification time for composite with porosity of 90% is
nearly half of that of composite with porosity of 95%.
III. Summary
S
No
Author PCM Used Nature of
PCM
Additives Result
1 H. Yin et al. [1] Paraffin Organic Expanded Graphite It is seen that when paraffin is absorbed in EG heat release period and
heat storage period is reduced by 26.2% and 65.3%
2 C. Lin et al. [2] Paraffin Organic Graphite Sheets It is seen that in thermal conductivity of composite reaches to 3.95W/mK
which 0.16W/mK of pure PCM was.
Further there is decrease in latent heat by 41.8 kJ/kg.
3 F. Yavari et al. [3] 1-
octadecanol
Organic Graphene Thermal conductivity rises to 140% on adding 4% of graphene and heat
of fusion decrease to 15.4%.
4 Wang et al. [4] PEG Organic Silica gel and β-
Aluminum Nitride
powder
It is observed that there is melting temperature does not change but there
is increase in thermal conductivity from 0.3847W/mK to 0.7661W/mK
5 O. Sansui et al. [5] Paraffin Organic GNF It is observed that GNF reduces solidification time by 61% over pure
paraffin at aspect ratio of 1
6 G. Xin et al. [6]
1-
Octadecano
l
Organic Graphene Sheet At 10% weight there is increase in thermal conductivity to 600% of
composite as compared to that of pure PCM
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7 X. Yang et al. [7] Myristic
Acid-
Myristic
Acid-
Palmitic
Acid
Ternary
Eutectic
Mixture
Expanded Graphite Melting Temperature of composite 41.64oC
Freezing Temperature of composite 42.99 oC
Latent heat of melting and freezing are 153.5J/g and 151.4J/g
At 1000 thermal cycle latent heat changes 1.63% and 1.32% respectively.
8 Wang et al. [8] PEG Organic Silicon dioxide It is seen that there is decrease in latent heat to 162.2J/g from 187.3J/g
and thermal conductivity increase to 0.3615W/mK which is 21% of
thermal conductivity at 0% of silicon di oxide.
9 B. Wu and Y. m.
Xing [9]
Paraffin Organic Graphite foam With porosity of 0.95% heat transfer of composite is approx. 3 times of
pure PCM.
10 A. Trigui and M.
Karkri [10]
Paraffin Organic composite
paraffin/epoxy
resin/copper tube (1)
and paraffin/epoxy
resin/brass tube (2)
It was seen that thermal conductivity of composite PCM was higher in
liquid state than pure PCM. While thermal conductivity of sample (1) was
higher than sample (2)
11 X. Fang et al. [11] Eicosane Organic GNP At 10% of GNP thermal conductivity reaches to 400% of pure PCM at 10
oC.
12 J. M. Marin et al.
[12]
Paraffin Organic Graphite Time taken to reach zero heat exchange of composite is nearly 50% lower
than pure PCM
13 A. Sari [13] Paraffin Organic High density
Polyethylene
It is seen that maximum percent of PCM in composite without leakage
was 77%. Thermal Conductivity of P1/HDPE and P2/HDPE increase to
14% and 24% respectively.
14 W. G. Alshaer et al.
[14]
RT-65 Organic CF-20 and KL1-250
and MWCNT
It was seen that CF-20 was more effective as compared to KL1-250
15 A. Babapoor et al.
[15]
Paraffin Organic Carbon Fiber At 0.46% mass of Carbon fiber maximum temperature rise reduced to
45%
16 Z. Ling et al. [16] RT44HC Organic Expanded Graphite On increase in mass fraction of EG there is increase in thermal
conductivity up to 60 times
17 L. Zhang et al. [17] PEG/PMM
A
Organic GNP At 8% of GNP thermal conductivity increased to 9 times that of pure
PCM
18 R. J.
Warzoha et al. [18]
Paraffin Organic Herringbone style
graphite nanofibers
It was observed that HGNF /PCM thermal conductivity increase
exponentially in Paraffin solid phase.
19 Z. Zhang et al. [19] Paraffin Organic Expanded Graphite It was seen that there is decrease in latent heat on adding EG to paraffin.
Latent heat reaches to 170.3J/g as compared to pure PCM which was
188.2J/g.
20 Z. Li and Z. G. Wu
[20]
Sodium
Nitrate
Inorganic Copper matrix Doped NaNO3 shows 80% reduced melting time than pure NaNO3, heat
transfer coefficient increased by 28.1 times in solid phase.
21 L. Zhong et al. [21] Binary
molten salts
Inorganic Expanded graphite Thermal conductivity increased by 4.9-6.9 times when impregnated with
EG
22 F. Frusteri et al. [22] PCM44 Inorganic Carbon fiber Thermal conductivity quadruples at 7% of fiber loading wt%
23 C. Y. Zhao and Z.
G. Wu [24]
NiNO3 Inorganic Metal Foam/expanded
Graphite
It was seen that heat transfer can be increased with both metal foam and
EG, but metal foam gives maximum performance.
The findings from the summarized result indicate that the Graphene/Expanded graphite/GNF composites increase the thermal
conductivity in the range of 19-60 times their non-doped organic samples and decrease latent heat values; the dispersion of
heat channels inside the composite significantly lower the melting time and solidification time. The inorganic composites
however show improvement in the melting times and heat transfer coefficients, the conductivity increase being not as
significant as their organic counterparts are.
IV. Conclusion
On studying to conventional active cooling by forced
air/liquid convection which is cumbersome and complex,
the passive thermal management system based on phase
change materials shows highlights of high efficiency,
compactness, no extra power input and the very simplicity.
However, the phase change materials with proper phase
transition temperatures are useful in keeping the
temperature of electronic devices within the desired range
for a long duration. The low thermal conductivity of
traditional organic and inorganic phase change materials
thwart rapid heat liberation from electronic system to
phase change materials and the augmentation of heat cause
to an extra high temperature. On reviewing works on
PCM-based thermal energy storage system, it is seen
expanded graphite and metal foam has been to be
efficacious in enhancing the thermal conductivity and
controlling temperatures of phase change materials. The
thermal properties which extracted from various research
works are: thermal conductivity, latent heat, temperature
variation, thermal storage performance and thermal
recyclability. Thermal conductivity can be enhanced by
International Journal for Research in Engineering Application & Management (IJREAM)
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inserting expanded graphite matrix in to PCM matrix or by
inserting foam in PCM. Although PCMs have large
amount of latent heat, but it decreases on incorporating
additives. Application of the passive thermal management
system is not suitable for devices operating non-
periodically.
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