A phase change material (PCM) is a substance with a high heat of fusion which, melting and solidifying at a certain temperature, is capable of storing and releasing large amounts of energy. Heat is absorbed or released when the material changes from solid to liquid and vice versa; thus, PCMs are classified as latent heat storage (LHS) units.

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SHRI RAMSWAROOP MEMORIAL UNIVERSITY
LUCKNOW (U.P.)
DEPARTMENT OF MECHANICAL ENGINEERING
PROJECT REPORT
ON
PHASE CHANGE OF MATERIAL
SUBMITTED BY:-
Shashwat Mishra

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Contents
1.Introduction Page No
1.1 Characteristics and classification………………………………………………………………………. 01
1.2 Organic PCMs…………………………………………………………………………………………………… 02
1.3 Inorganic………………………………………………………………………………………………………….. 03
1.4 Eutectics………………………………………………………………………………………………………….. 04
1.5 Hygroscopic materials……………………………………………………………………………………… 05
2. Selection criteria………………………………………………………………………………… 06
3. Thermophysical properties………………………………………………………………… 08
3.1 Common PCMs…………………………………………………………………………………………………. 09
3.2 Commercially available PCMs near room temperature……………………………………… 10
4. Technology, development and encapsulation……………………………………. 11
5. Thermal composites…………………………………………………………………………. 12
6. Applications……………………………………………………………………………………… 13
7. Fire and safety issues……………………………………………………………………….. 14
8. References………………………………………………………………………………………. 19

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List of figure Page No
Fig01……………………………………………………………………………………………………………………….o4
Figo2……………………………………………………………………………………………………………………….o9
Fig03………………………………………………………………………………………………………………………..15
Fig04………………………………………………………………………………………………………………………..16

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Phase-change material
A phase change material (PCM) is a substance with a high heat of fusion which, melting and
solidifying at a certain temperature, is capable of storing and releasing large amounts of energy.
Heat is absorbed or released when the material changes from solid to liquid and vice versa;
thus, PCMs are classified as latent heat storage (LHS) units. Research in the use of phase change
materials for buildings has successfully shown that use of phase change materials results in
savings and the environmentally benign use of premium energy. Research work in thermal
comfort using phase change materials needs to be more compatible with other building
materials.
The effect of mixing of different phase change materials and ensuing chemical processes on the
melting point and latent heat was reviewed. the production of nanocomposite-enhanced
phase-change materials (NEPCMs) using the direct-synthesis method by mixing paraffin with
alumina (Al2O3), titania (TiO2), silica (SiO2), and zinc oxide (ZnO) as the experimental samples.
Al2O3, TiO2, SiO2, and ZnO were dispersed into three concentrations of 1.0, 2.0, and 3.0 wt.%.
Through heat conduction and differential scanning calorimeter experiments to evaluate the
effects of varying concentrations of the nano-additives on the heat conduction performance
and thermal storage characteristics of NEPCMs, their feasibility for use in thermal storage was
determined. The experimental results demonstrate that TiO2 is more effective than the other
additives in enhancing both the heat conduction and thermal storage performance of paraffin
for most of the experimental parameters.
Furthermore, TiO2 reduces the melting onset temperature and increases the solidification onset
temperature of paraffin. This allows the phase-change heat to be applicable to a wider
temperature range, and the highest decreased ratio of phase-change heat is only 0.46%,
compared to that of paraffin. Therefore, this study demonstrates that TiO2, added to paraffin to
form NEPCMs, has significant potential for enhancing the thermal storage characteristics of
paraffin.

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Characteristics and classification
Fig.1
Latent heat storage can be achieved through liquid–>solid, solid–>liquid, solid–>gas and liquid–
>gas phase changes. However, only solid–>liquid and liquid–>solid phase changes are practical
for PCMs. Although liquid–gas transitions have a higher heat of transformation than solid–liquid
transitions, liquid->gas phase changes are impractical for thermal storage because large
volumes or high pressures are required to store the materials in their gas phase. Solid–solid
phase changes are typically very slow and have a relatively low heat of transformation.
Initially, solid–liquid PCMs behave like sensible heat storage (SHS) materials; their temperature
rises as they absorb heat. Unlike conventional SHS materials, however, when PCMs reach the
temperature at which they change phase (their melting temperature) they absorb large
amounts of heat at an almost constant temperature. The PCM continues to absorb heat

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without a significant rise in temperature until all the material is transformed to the liquid
phase. When the ambient temperature around a liquid material falls, the PCM solidifies,
releasing its stored latent heat. A large number of PCMs are available in any required
temperature range from −5 up to 190 °C.[1] Within the human comfort range between 20–30
°C, some PCMs are very effective. They store 5 to 14 times more heat per unit volume than
conventional storage materials such as water, masonry or rock.
1. Organic PCMs
Paraffin (CnH2n+2), carbohydrate and lipid derived.
Salt hydrate phase change materials used for thermal storage in space heating and
cooling applications have low material costs, but high packaging costs. A more economic
installed storage may be possible with medium priced, high latent heat organic
materials suitable for low cost packaging, i.e. those that are insoluble in water and
unreactive with air and some of the common packaging films. We have done a
preliminary survey of 12 such organic materials with melting points in the range 10–
43°C. Measurements of melting point, freezing point, and the latent heats of melting
and fusion are presented. For distributed passive solar storages, butyl stearate, m.p. =
19°C, f.p. = 21°C, ΔHm = 120 J/g, current cost 55¢/lb, seem promising. For central
storage, both vinyl strearate, m.p. = 27°C, f.p. = 29°C, †Hm = 122 J/g, and mixtures of
ethoxylated (C11-C15) linear alcohols, 30°C < m.p. < 41°C, 31°C < 40°C, 105 J/g < ΔHm <
134 J/g, current costs between 38¢/lb and 57¢/lb, for average molecular weights
between 1080 and 1520, warrant further study. Isopropyl stearate, m.p. = 14°C, f.p. =
18°C, ΔHm = 142 J/g, should be considered as a “coolness” storage for desert regions.
Advantages
1. Freeze without much undercooling
2. Ability to melt congruently
3. Self nucleating properties

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4. Compatibility with conventional material of construction
5. No segregation
6. Chemically stable
7. High heat of fusion
8. Safe and non-reactive
9. Recyclable
10. Carbohydrate and lipid based PCMs can be produced from renewable sources
Disadvantages
Low thermal conductivity in their solid state. High heat transfer rates are required during the
freezing cycle
1. Volumetric latent heat storage capacity can be low
2. Flammable. This can be partially alleviated by specialist containment
3. To obtain reliable phase change points, most manufacturers use technical grade
paraffins which are essentially paraffin mixture(s) and are completely refined of oil,
resulting in high costs
2. Inorganic
Salt hydrates (MnH2O)
Advantages
1. High volumetric latent heat storage capacity
2. Availability and low cost
3. Sharp melting point
4. High thermal conductivity

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5. High heat of fusion
6. Non-flammable
Disadvantages
1. Change of volume is very high
2. Super cooling is major problem in solid–liquid transition
3. Nucleating agents are needed and they often become inoperative after repeated cycling
4. Infinite R Energy Sheet
Example eutectic salt hydrate PCM with nucleation & gelling agents for long term thermal
stability and thermoplastic foil macro-encapsulation physical durability. Applied for passive
temperature stabilization to result in building HVAC energy conservation.
Eutectics
c-inorganic, inorganic-inorganic compounds
Advantages
1. Eutectics have sharp melting point similar to pure substan
2. Volumetric storage density is slightly above organic compounds
Extra water principle can be used to avoid phase change degradation, involving dissolving the
anhydrous salt during melting to result in a thickening of the liquid material so that it melts to a
gel form
Disadvantages
1. Only limited data is available on thermo-physical properties as the use of these
materials are relatively new to thermal storage application

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Hygroscopic materials
Many natural building materials are hygroscopic, that is they can absorb (water condenses) and
release water (water evaporates). The process is thus:
1. Condensation (gas to liquid) ΔH<0; enthalpy decreases (exothermic process) gives off
heat.
2. Vaporization (liquid to gas) ΔH>0; enthalpy increases (endothermic process) absorbs
heat (or cools).
Whilst this process liberates a small quantity of energy, large surfaces area allows significant (1–
2 °C) heating or cooling in buildings. The corresponding materials are wool insulation,
earth/clay render finishes,.
Selection criteria
Thermodynamic properties. The phase change material should possess:
1. Melting temperature in the desired operating temperature range
2. High latent heat of fusion per unit volume
3. High specific heat, high density and high thermal conductivity
Small volume changes on phase transformation and small vapor pressure at operating
temperatures to reduce the containment problem
1. Congruent melting
2. Kinetic properties
High nucleation rate to avoid supercooling of the liquid phaseHigh rate of crystal growth, so
that the system can meet demands of heat recovery from the storage system
Chemical properties
1. Chemical stability
2. Complete reversible freeze/melt cycle
3. No degradation after a large number of freeze/melt cycle

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4. Non-corrosiveness, non-toxic, non-flammable and non-explosive materials
Fig.2
Economic properties
1. Low cost
2. Availability
Technology, development and encapsulation
The most commonly used PCMs are salt hydrates, fatty acids and esters, and various paraffins
(such as octadecane). Recently also ionic liquids were investigated as novel PCMs.
As most of the organic solutions are water-free, they can be exposed to air, but all salt based
PCM solutions must be encapsulated to prevent water evaporation or uptake. Both types offer
certain advantages and disadvantages and if they are correctly applied some of the
disadvantages becomes an advantage for certain applications.

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They have been used since the late 19th century as a medium for the thermal storage
applications. They have been used in such diverse applications as refrigerated
transportation[90] for rail[91] and road applications[92] and their physical properties are,
therefore, well known.
Unlike the ice storage system, however, the PCM systems can be used with any conventional
water chiller both for a new or alternatively retrofit application. The positive temperature
phase change allows centrifugal and absorption chillers as well as the conventional
reciprocating and screw chiller systems or even lower ambient conditions utilizing a cooling
tower or dry cooler for charging the TES system.
The temperature range offered by the PCM technology provides a new horizon for the building
services and refrigeration engineers regarding medium and high temperature energy storage
applications. The scope of this thermal energy application is wide ranging of solar heating, hot
water, heating rejection, i.e. cooling tower and dry cooler circuitry thermal energy storage
applications.
Since PCMs transform between solid–liquid in thermal cycling, encapsulation[93] naturally
become the obvious storage choice.
Encapsulation of PCMs
Macro-encapsulation: Early development of macro-encapsulation with large volume
containment failed due to the poor thermal conductivity of most PCMs. PCMs tend to solidify at
the edges of the containers preventing effective heat transfer.
Micro-encapsulation: Micro-encapsulation on the other hand showed no such problem. It
allows the PCMs to be incorporated into construction materials, such as concrete, easily and
economically. Micro-encapsulated PCMs also provide a portable heat storage system. By
coating a microscopic sized PCM with a protective coating, the particles can be suspended
within a continuous phase such as water. This system can be considered a phase change slurry
(PCS).

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Molecular-encapsulation is another technology, developed by Dupont de Nemours that allows
a very high concentration of PCM within a polymer compound. It allows storage capacity up to
515 kJ/m2 for a 5 mm board (103 MJ/m3). Molecular-encapsulation allows drilling and cutting
through the material without any PCM leakage.
As phase change materials perform best in small containers, therefore they are usually divided
in cells. The cells are shallow to reduce static head – based on the principle of shallow container
geometry. The packaging material should conduct heat well; and it should be durable enough
to withstand frequent changes in the storage material's volume as phase changes occur. It
should also restrict the passage of water through the walls, so the materials will not dry out (or
water-out, if the material is hygroscopic). Packaging must also resist leakage and corrosion.
Common packaging materials showing chemical compatibility with room temperature PCMs
include stainless steel, polypropylene and polyolefin.
Thermal composites
Thermal-composites is a term given to combinations of phase change materials (PCMs) and
other (usually solid) structures. A simple example is a copper-mesh immersed in a paraffin-wax.
The copper-mesh within parraffin-wax can be considered a composite material, dubbed a
thermal-composite. Such hybrid materials are created to achieve specific overall or bulk
properties.
Thermal conductivity is a common property which is targeted for maximisation by creating
thermal composites. In this case the basic idea is to increase thermal conductivity by adding a
highly conducting solid (such as the copper-mesh) into the relatively low conducting PCM thus
increasing overall or bulk (thermal) conductivity. If the PCM is required to flow, the solid must
be porous, such as a mesh.
Solid composites such as fibre-glass or kevlar-pre-preg for the aerospace industry usually refer
to a fibre (the kevlar or the glass) and a matrix (the glue which solidifies to hold fibres and
provide compressive strength). A thermal composite is not so clearly defined, but could

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similarly refer to a matrix (solid) and the PCM which is of course usually liquid and/or solid
depending on conditions. They are also meant to discover minor elements in the earth.
Applications:
1. Air Condition:
Until very recently, pcms were not reliable enough to be used in air condition. We have
developed pcm with almost infinite life and good performance in the human comfort range of
18C (64F) to 29C (84F) and further for electronic comfort at higher temperature.
2. Telecom Shelters:
Telecom shelters are insulated, air-conditioned enclosures that house the heart of mobile
communication, the Base Transceiver Station (BTS). BTS, and also the battery, is very
temperature sensitive and its surroundings should always be maintained below 35 deg C. In
under-developed countries, there are frequent power cuts and single phasing, forcing cellular
service providers to install Diesel Generators to support the air-conditioner in case of power cuts
or single phasing. Phase Change Material PCM installed in Telecom Shelter will absorb heat in
case of unavailability of power, minimizing/eliminating use of DG Sets. PCM will get re-
charged when power source is available. Thus, PCM store energy using a cheap source of power
and release it when that cheap source of power is not available, thus saving on Diesel Cost.
3. Transportation:
Transportation of perishable foods, temperature sensitive pharmaceuticals, sundry electronics
(like ignition transformers) and chemicals (explosives) require refrigerated trucks. Such
refrigerated trucks are prohibitively expensive to operate as they use Diesel as a source of
energy. Cost of diesel-generated energy is 6 times higher as compared to conventional
electricity cost. Thus, Phase Change Material store energy using a cheap source of power and
release it when that cheap source of power is not available.

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4. Automobiles
PCM is already used today in a latent heat battery offered by BMW as optional equipment in its
5 series. The principle is quite simple, the storage material is connected to the radiator and stores
excess heat when the motor runs at operating temperature. This heat is then available at the next
cold start to heat up the motor quickly (better gas mileage) and for the interior (driving comfort).
Due to the latent heat battery’s excellent insulation, it can maintain the energy for 2 days at an
outside temperature of – 20°C. As an extension to this application, PCM can also be used in tail-
pipes (exhaust) of vehicles. This will maintain the catalytic converter at its design temperature,
reducing excessive Hydro-carbon emissions during vehicle start up.
5. House heating, warm water:
Solar energy is not available at all times, and therefore solar installations require an intermediary
storage of the energy for heating or warm water. PCM based system will offer the following
benefits over a conventional system: Low volume in comparison to water storage systems and a
higher efficiency due to a lower temperature difference between loading and discharging of the
energy. Latent heat storage can also be implemented in conventional heating systems. Phase
Change Material based solar water heater will also give a better controlled water temperature.
6. Construction materials:
The atmosphere in a room is found comfortable if it varies little in the course of the day. For this
reason, homes with very thick walls are found especially comfortable: cool in the summer and
warm in the winter. To achieve this comfort in less massive constructions, one can implement
materials containing PCM and thus demonstrating the same properties as thick walls. By
absorbing heat at the peaks (e.g. during sunshine) and delayed release in the night, in most cases
one can even do without air conditioning.
7. Catering:
The transportation of warm meals requires a heat source; otherwise it will not meet the quality
standards set by the consumers. An electric heating source cannot always be implemented, in
such cases Phase Change Material offer an ideal, self-regulating heating element. The melting

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point of the PCM depends upon the temperature at which the food should be kept. 60° – 70°C are
optimal so that the food does not continue to cook but is hot enough to eat.
8. Electronics:
Electronic circuitry is extremely sensitive to over-heating, negatively influencing both lifetime
and reliability of the parts. To date, metal fins are used for heat sinking improving their cooling
capacity with additional fans. The sinking of heat peaks using PCM is absolutely reliable since
no motor or temperature measurements are required. The PCM regenerates itself between peaks
by emitting the heat with cooling fins. The advantage is a smaller cooling system with a very
high reliability.
9. Green Houses:
It is important to maintain temperatures in a small range to enable plants cultivated in a green
house to flourish. However, due to large temperature swings in daytime and nighttime
temperatures, most green houses need air-conditioning and/or heating. Phase Change Material
installed in floor of such green houses will eliminate or reduce the dependence on air-
conditioning/heating.
1. Phase-change material being employed in the treatment of neonates with birth
asphyxia.
2. Thermal energy storage
3. Solar cooking
4. Cold Energy Battery
5. Conditioning of buildings, such as 'ice-storage'
6. Cooling of heat and electrical engines
7. Cooling: food, beverages, coffee, wine, milk products, green houses
Medical applications: transportation of blood, operating tables, hot-cold therapies, treatment
of birth asphyxia

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Fig.3
Human body cooling under bulky clothing or costumes.
1. Waste heat recovery
2. Off-peak power utilization: Heating hot water and Cooling
3. Heat pump systems
4. Passive storage in bioclimatic building/architecture (HDPE, paraffin)
5. Smoothing exothermic temperature peaks in chemical reactions
6. Solar power plants
7. Spacecraft thermal systems
8. Thermal comfort in vehicles
Thermal protection of electronic devices
1. Thermal protection of food: transport, hotel trade, ice-cream, etc.
2. Textiles used in clothing

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3. Computer cooling
4. Turbine Inlet Chilling with thermal energy storage
Fig.4
Telecom shelters in tropical regions. They protect the high-value equipment in the shelter by
keeping the indoor air temperature below the maximum permissible by absorbing heat
generated by power-hungry equipment such as a Base Station Subsystem. In case of a power
failure to conventional cooling systems, PCMs minimize use of diesel generators, and this can
translate into enormous savings across thousands of telecom sites in tropics.
The main advantage of PCM is the hability to store large amounts of energy, nevertheless, their
thermal conductivity can be more than one order of magnitude higher than typical insulator
materials. Thus, the use of PCM or thermal insulator materials or both should take in to account
not only the thermal conductivity but the combination of thermal conductivity, heat capacity
and density, i.e. thermal diffusivity (in cases of insulator materials) and the combination of
thermal diffusivity and the Stefan number in cases of PCM.

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It is found that PCM in the building envelope helped to shield the building against heat transfer
under certain weather conditions. We optimized the melting temperature and the position of
the PCM in the envelope.
The TMY3 weather data is used to provide boundary conditions on exterior side of the wall with
indoor environment being set at 24C in summer and 22C in winter. Using standalone module,
the results were amazing!!! In some high latent heat cases with narrow melting range, we could
eliminate the heat transfer through walls during summer where the walls became adiabatic!!!.
The heat is stored by PCM during the day and released back to outside during the night. The
climate was the driving potential for charging and discharging the PCM. The results were
amazing and so we have integrated those modules in TRNSYS, a whole-building simulation tool.
Real boundary conditions were applied in this case. The indoor environment has many heat
sources such as internal heat gain from people, lights, equipment with solar penetrating
through windows, and air infiltration. The maximum savings in peak and annual loads were not
so amazing at all for four climates in USA. The maximum saving was below 15%, even for high
latent cases that used to make the walls adiabatic in standalone cases. For the same house in
TRNSYS, I then applied ideal sinusoidal boundary conditions to see the potential of PCM. The
results are amazing . Therefore, PCM’s performance is so tricky with climate generally being the
driving potential!
Drawbacks:
1. Fire and safety issues
Some phase change materials are suspended in water, and are relatively nontoxic. Others are
hydrocarbons or other flammable materials, or are toxic. As such, PCMs must be selected and
applied very carefully, in accordance with fire and building codes and sound engineering
practices. Because of the increased fire risk, flamespread, smoke, potential for explosion when
held in containers, and liability,

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it may be wise not to use flammable PCMs within residential or other regularly occupied
buildings. Phase change materials are also being used in thermal regulation of electronics.

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References
Kenisarin, M; Mahkamov, K (2007). "Solar energy storage using phase change materials".
Renewable and Sustainable Energy Reviews. 11 (9): 1913–1965. doi:10.1016/j.rser.2006.05.005.
Sharma, Atul; Tyagi, V.V.; Chen, C.R.; Buddhi, D. (2009). "Review on thermal energy storage
with phase change materials and applications". Renewable and Sustainable Energy Reviews. 13
(2): 318–345. doi:10.1016/j.rser.2007.10.005.
"Heat storage systems" (PDF) by Mary Anne White, brings a list of advantages and
disadvantages of Paraffin heat storage. A more complete list can be found in AccessScience
website from McGraw-Hill, DOI 10.1036/1097-8542.YB020415, last modified: March 25, 2002
based on 'Latent heat storage in concrete II, Solar Energy Materials, Hawes DW, Banu D,
Feldman D, 1990, 21, pp.61–80.
Floros, Michael C.; Kaller, Kayden L. C.; Poopalam, Kosheela D.; Narine, Suresh S. (2016-12-01).
"Lipid derived diamide phase change materials for high temperature thermal energy storage".
Solar Energy. 139: 23–28. doi:10.1016/j.solener.2016.09.032.
Agyenim, Francis; Eames, Philip; Smyth, Mervyn (2011-01-01). "Experimental study on the
melting and solidification behaviour of a medium temperature phase change storage material
(Erythritol) system augmented with fins to power a LiBr/H2O absorption cooling system".
Renewable Energy. 36 (1): 108–117. doi:10.1016/j.renene.2010.06.005.
See above: 'Heat Storage Systems' (Mary Anne White), page 2
"Infinite R™ | Phase Change Materials | Thermal Storage | Insolcorp, Inc – Phase Change
Materials for Buildings & Environment". Infinite R™ | Phase Change Materials | Thermal
Storage | Insolcorp, Inc. Retrieved 2017-03-01.