Phase Change Materials

The phase change material (PCM) cooling approach is unstable during long-cycle scenario limited by the poor thermal conductivity [11,12].

From: Handbook of Thermal Management Systems, 2023

Microencapsulated thermal storage materials for solar desalination process: an advanced technique for hygienic water production

Dilshad Ali, ... B. Srinivasarao Naik, in Water, The Environment, and the Sustainable Development Goals, 2024

18.2.3.1 Macro encapsulation

The PCM is encapsulated in 1 mm or 1 cm of the shell. The growth and effectiveness of the SD process are significantly influenced by the choice of PCM and shell materials for macro encapsulation. This method can contain a sizable amount of PCM.19 Macro encapsulation of PCM in SD, copper, or aluminum containers is required for PCM’s thermal conductivity enhancement.

As discussed in Table 18.1, the organic PCMs have less thermal conductivity. Lower thermal conductivity PCM may affect sustainable water productivity. The thermal conductivity of containers has been provided in Table 18.2 for a better understanding of the materials.

Table 18.2. Thermal conductivity of container.20

Container for PCMThermal conductivity (W/m.K)
Aluminum235
Copper401

Elashmawy et al.21 filled PCM in aluminum containers to improve heat transfer and copper rods were placed inside aluminum tubes. The outcomes demonstrated a significant improvement in SD system performance and distillation productivity at a cheap cost. The effectiveness and productivity of the designed system were increased by 38.3% and 40.5%, respectively. Additionally, the designed system’s yield, efficiency, and price per litre are 5.6 L/m2 day, 44.0%, 0.008 USD, and 4.0 L/m2 day, 32%, 0.02 USD, respectively. Kabeel et al.22 also tested with PCM in a copper tube to improve diurnal and nocturnal distillation. They reported a considerable increase in productivity using copper-filled PCM in tubes. Time, container thickness, and PCM mass are vital in the system’s design. PCM and non-PCM water distillation productivities were about 5780 and 5331 mL/m2 day, respectively. Additionally, solar still with PCM had 8% higher production efficiency than traditional ones (non-PCM).23 The daily efficiency for developed tubular SS and traditional SS with PCM range from 37.2% to 38.1% to 44.2%–45.3%. It means that water productivity with PCM depends on solar still design.

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A novel cooling strategy for lithium-ion battery thermal management with phase change material

Manish K. Rathod, Jay R. Patel, in Handbook of Thermal Management Systems, 2023

4.3.2 Liquid-cooled PCM-based cooling strategy

PCM-liquid flow hybrid cooling is the latest battery thermal management innovation. Due to its higher thermal conductivity, liquid cooling dominates PCM solidification over air cooling. Fig. 7 illustrates PCM/liquid-based hybrid BTMS operation. PCM surrounds the battery cells, and pipelines allow liquid to flow through them.

Fig. 7

Fig. 7. Schematic of air-cooled PCM-based cooling strategy [50].

Zhang et al. [51] presented a hybrid PCM-and-liquid-cooling BTM. Integrating PCM with a liquid thermal management scheme allows the system to meet heat dissipation demands even in the most severe operating circumstances. Latent heat maintained the battery pack’s operational temperature. When a cell ran out of control, much of the PCM latent heat was consumed. After liquid cooling began, the cooling channel extracted heat from the aluminum plate, preventing runaway heat and heat transmission to neighboring cells. Song et al. [52] suggested a unique conjugate cooling structure that combines PCM and liquid cooling technologies. When compared to a single PCM or liquid cooling condition, cell temperature, and temperature uniformity were significantly reduced by conjugate cooling. Hekmat et al. [53] introduced a hybrid BTMS for high-capacity Li-ion prismatic batteries that blend PCM with a conventional cooling system. Compared to traditional BTMs, hybrid models benefit from a significantly lower maximum temperature due to PCM’s cooling water pipe system.

Using a PCM/liquid cooling system, An et al. [54] discovered that temperatures could be maintained in a desirable range up to a moderate discharge rate. However, it was found to be too high at a discharge rate of more than 3C. Therefore, the impact of adding EG to pure PCM was explored with a weight percentage of six on temperature rise over a range of flow rates. At a flow velocity of 0.14 m/s, maximum temperatures of 46.3°C and maximum temperature differences of 2°C were achieved, while CPCM with 6 wt.% EG shows improved performance even at a flow velocity of 0.04 m/s. Similarly, liquid cooling and composite PCM were combined in the hybrid BTMS created by Cao et al. [55]. The PCM/EG composite was then added to the battery pack, and the water tubes were run via PCM. After examining battery performance with solely liquid cooling, researchers looked at two distinct hybrid BTMS, one with a 25% EG mass fraction and the other with a 67% EG mass fraction. With 67 wt.% EG/RT44HC, the battery temperature dropped by 16%.

Cao et al. [56] also examined the combination of PCM and water cooling. The reversal of flow from parallel to counter enhanced temperate uniformity significantly, along with a minor improvement in battery temperature. In addition, a novel strategy of delayed cooling was proposed and suggested initiating liquid flow after the temperature of the battery reached 41°C. This technique maintained similar battery performance while consuming less energy.

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Solar Thermal Systems: Components and Applications

D. Kolokotsa, ... T. Karlessi, in Comprehensive Renewable Energy, 2012

3.19.2.2 Use of Phase Change Materials to Enhance the Performance of Cool-Colored Coatings

Phase change materials (PCMs) may store heat in their mass under the form of latent heat. PCMs are widely used in solar applications as well as in building materials, like plaster, to absorb the excess heat in buildings. Microencapsulated PCMs are commercially developed and are available at a particle size ranging between 17 and 20 μm. Microparticles include a phase change ingredient, usually paraffins, in their core and a polymer or a plastic in the exterior shell. The melting temperature may vary according to the specific needs.

Phase change microparticles have been used to further enhance the performance of cool color coatings. They have been used to develop coatings based on infrared reflective pigments doped with PCMs [33]. Six different colored pigments have been tested while investigations have been performed regarding the melting temperature of the microcapsules and the weight percentage of the materials. The PCM-doped coatings as well as the conventional infrared reflective and the common coatings have been used to paint concrete tiles, and their surface temperature has been measured during the summer of 2008 (Figure 13). Surface temperature sensors and infrared thermography techniques have been used.

Figure 13. Picture of the tested cool phase change coatings.

Measurements have shown that the PCM-doped materials present a peak daily temperature of up to 4 °C lower compared to conventional infrared reflective coatings and up to 9 °C compared to common coatings.

Figure 14 shows the daily variation of the surface temperature of black tiles, coated with PCM-doped, conventional infrared reflective, and common black coatings, for 10 consecutive days of measurements. As shown, during the whole measurement period, the peak surface temperature of PCM-doped coatings was in all cases 2–4 °C lower than that of the conventional infrared reflective coatings. During the night period, both the PCM-doped and the conventional infrared reflective coatings presented substantially lower surface temperatures than the common black paints.

Figure 14. Daily variation of the surface temperature of black tiles coated with phase change material (PCM)-doped, conventional infrared reflective, and common black coatings.

The measured temperature difference between the PCM-doped and the conventional infrared reflective coatings varies during the day, presenting its maximum during the morning hours when the surface temperature approaches the melting point of the PCM.

Figure 15 shows the daily variation of the surface temperature difference between the PCM-doped and the conventional infrared reflective coatings together with the daily variation of the temperature of the conventional infrared reflective material. As shown, the maximum temperature difference between the two coatings is seen at about 9.30 a.m. when the temperature of the material reaches the fusion temperature of the PCM. At that time, the temperature difference between the two materials varies between 8 and 10 °C.

Figure 15. Daily variation of the surface temperature difference between the phase change material (PCM)-doped and the conventional infrared reflective coatings. Also, the daily variation of the conventional infrared reflective material is shown.

Figure 16 shows the daily variation of both the PCM-doped and the conventional infrared reflective materials. During the night period, both materials present a similar temperature. At about 8.00 a.m., the PCM starts to melt and the surface temperature of this coating presents a much lower increase than that of the conventional one, until 9.30 a.m., when the maximum surface temperature difference is achieved. At that time, convective phenomena between the tiles and the ambient air are much more intensive for the PCM-doped coating as its surface temperature is considerably lower. Thus, the rate of increase of the surface temperature of the PCM-doped material starts to be much higher than that of the conventional coating and this continues until the early afternoon period when surface temperatures reach their maximum. In the afternoon period, the rate of decrease of the surface temperature of the PCM-doped material is quite lower until the sunset when both materials present almost a similar temperature. During the night period, latent heat released by the PCM-doped material does not have any significant impact on the surface temperature of the coating.

Figure 16. Daily variation of the surface temperature of the common, conventional infrared reflective, and phase change material (PCM) 28 ° C and PCM 24 ° C doped infrared reflective black coatings.

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Strategies for thermal management of electronics: Design, development, and applications

Sadeq Hooshmand Zaferani, ... Reza Ghomashchi, in Handbook of Thermal Management Systems, 2023

5.1 Phase change materials

Phase Change Materials (PCMs) can store thermal energy with a negligible temperature change and demonstrate the same properties under several cycles. However, low thermal conductivity is the chief disadvantage of PCMs, specifically for the ones with low phase transition temperature [84,106,107]. An experimental study [108] analyzed the effective parameters for the performance of the round pin-finned heat sinks in cooling mobile electronic devices. In this design, paraffin was used as the PCM under the volume fractions of 0, 0.5, and 1.0 poured in each configuration of pin-fin heat sinks. The pin-fins were fabricated from aluminum with diameters of 2 mm, 3 mm, and 4 mm. According to the results, the heat sink with a diameter of 3 mm has the best heat dissipation.

Fig. 4 demonstrates various examples of PCM in the cooling systems for electronic devices.

Fig. 4

Fig. 4. Applications of PCM as heat sinks for thermal management of electronics: (A) configuration of fin structures made by straight and arc fins to improve the heat transfer of battery thermal management systems (BTMSs) [109], (B) experimental prototypes to characterize PCM based heat sinks for cooling electronic devices: all heat sinks used were made of aluminum with dimensions of 80 × 62 × 25 mm3. Pin fins act as the thermal conductivity enhancer (TCE) to enhance the heat distribution homogeneously [102], (C) a plate-fin heat sink conductivity enhancer based on PCM to improve the heat transfer enhancement: (i) an isometric cross-sectional view of PCM filled finned heat sink assembly and (ii) schematic diagram of the physical domain. According to the results, a PCM-filled-plate-fin heat sink decreased the heat sink temperature and enhanced the consistency of PCM melting [110].

In this field, a study [111] investigated the heat transfer in electronic devices by employing closely-packed pin-fin heat sinks filled with PCM. Three pin-fin configurations, including rectangular, round, and triangular cross sections were used containing a fixed PCM volume fraction of 90%. Six PCMs were tested, namely, paraffin wax, RT-54, RT-44, RT-35HC, SP-31, and n-eicosane. The outcomes showed that the triangular pin-fins have the most effective thermal performance for both with and without PCM.

The longitudinal fins and cylindrical rings were evaluated by Sun et al. [112]. According to the results, the optimal numbers for rings and fins are 1 and 8, respectively. Another work [113] designed a 3-D printed PCM containment to combine a passive cooling solution for Building-Integrated Concentrated Photovoltaics (BICPV) by using micro-fins, PCM, and Nanomaterial Enhanced PCM (n-PCM). In comparison with micro-fins, the average temperature of the testing setup was decreased by 12.5 °C using micro-fins filled with n-PCM, respectively. In another work [114] n-eicosane and dodecanoic acid was used as the PCMs and an aluminum sheet with a thickness of 0.4 mm as a thermal spreader to design thin encapsulated PCM packages for thermal management of portable electronic devices. Compared to the reference setup with no spreader and PCM package, the heater and cover maximum temperatures were reduced by 45% and 42%, respectively.

For the flexible heat sink designs, paraffin@copper (PA@Cu) microcapsule with paraffin as core and nano-Cu particle as “flexible” metal shell was investigated [115]. In this design, the PA@Cu microcapsules were embedded into uncured liquid silicone to make flexible composite PCMs (PA@Cu/SE). A hybrid design combined the PCM and air to make a heat sink [116]. The outcome of this investigation showed that this heat sink with 50 Wm−2 K−1 can be comparable with air-cooled heat sinks with the convective heat transfer coefficient of 100 Wm−2 K−1.

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Passive thermal management systems for e-mobility using PCM composites

Mohamed Moussa El Idi, ... Mahamadou Abdou Tankari, in Handbook of Thermal Management Systems, 2023

1.3 PCMs

PCMs can store and release a large amount of heat during their phase change using relatively small volumes. Fig. 1 shows the principle of operation of PCMs. The first criterion for selecting a PCM is its energy density (Ls and Lf). Other constraints also influence the choice of a PCM for a specific application:

Fig. 1

Fig. 1. The operating principle of a PCM

Melting Temperature: The melting temperature is critical in PCM selection for a specific industrial application. The melting temperature must be consistent with the operating temperature of the system. The choice of a PCM without considering this criterion can lead to not using the phase change and thus using only sensible heat storage. The prior determination of the operating temperature of the system is crucial in the choice of the adequate PCM.

Thermal conductivity: in many applications, PCM is used to store/remove thermal energy in a specific time interval. The value of the thermal conductivity of the PCM is decisive for the phase change kinetics. The heat transfer intensity is directly related to thermal conductivity. A high thermal conductivity accelerates the phase change.

Supercooling: unlike melting, which always starts at the same temperature, crystallization does not take place at the liquid-solid equilibrium temperature (melting temperature) but at a lower temperature, which is the crystallization temperature. This is the difference between the melting temperature and the crystallization temperature. The liquid is then supercooled or metastable. The reduction of the supercooling is necessary so that the stored heat is resituated at the same temperature and to reduce the phase shift between the storage/release cycles.

Thermal cycling stability: Thermal cycling corresponds to the successive cycles of storage/de-storage (melting/solidification). They can result in the degradation of the thermophysical properties of the PCM and a decrease in their efficiency. It is essential to study the impact of cycles (melting/solidification) on a PCM’s phase change temperature, specific heat, and latent heat. Sharma et al. [3] studied the stability and degradation of the thermophysical properties of paraffin. After 300 cycles, paraffin lost about 10% of its latent heat and retained its specific heat. The results showed good stability of the paraffin and a very low degradation of the thermophysical properties. 300 cycles are relatively few compared to an industrial application.

Volume expansion: this is the increase in volume during the solid-liquid phase change. A small volume expansion allows both phases to be stored in the same volume. This is an issue in the sizing of the storage unit, especially when using a closed container. A volume more considerable than the PCM in the solid state must be provided to contain the PCM in the liquid state.

Chemical stability: the PCM used in a thermal storage unit will be in contact with a material that constitutes the containment. It is, therefore, necessary to ensure the compatibility of the PCM used with the material that constitutes its encapsulation.

Costs and availability: using a PCM for an industrial application requires its availability on a large scale. Also, the price is very important as it directly impacts the payback time. Too long payback times limit the attractiveness of a PCM.

1.3.1 Classification of PCMs

PCMs are classified into three major families: organic PCMs, inorganic PCMs, and eutectic PCMs [4–6]. Each group consists of several subgroups. Fig. 2 shows the different PCM families.

Fig. 2

Fig. 2. Classification of PCM.

Inorganic PCMs

The family of inorganic PCMs is composed mainly of salts, hydrates of salts, and metals. Salt hydrates are used first as a PCM to store thermal energy by phase change [7–9]. They are inorganic saline compounds containing water. They are obtained by mixing one and a—in principle—well-defined quantity of water. Salt hydrates generally have a high energy density (twice as high as the energy density of organic PCMs), a low volume expansion during phase change, and excellent thermal conductivity compared to other PCMs. We can distinguish three types of melting behavior of hydrated salts: congruent melting, semicongruent melting, and noncongruent melting. Congruent melting occurs when the salt is entirely soluble in the water of hydration at the melting temperature of the salt. The second behavior, semicongruent melting, occurs when there is an equilibrium between the solid and liquid phases during a transition. The last behavior occurs when the salt is not entirely soluble in the water of hydration. Hydrated salts have problems with phase segregation, latent heat degradation after a 1000 cycles (a drop that can reach more than 74% for some PCM), and supercooling.

The metals primarily include low melting point metals. Due to weight penalties, this type of PCM has yet to be seriously considered for thermal storage applications. Table 1 shows the thermophysical properties of some inorganic PCMs.

Table 1. Thermophysical properties of some inorganic PCMs.

PCMTmeltingkPLf
°CW/(m K)kJ/kg
LiClO3 · 3H2O [10]8.0253
KF · 4H2O [11,12]18.5–19231
CaCl2 · 6H2O [11–13]28–301.08–0.54190–200
Na2HPO4 · 12H2O [12]35–450.514–0.476279.6
Zn(NO3)2 · 6H2O [14]360.464146.9
Organic PCMs

Organic PCMs can be classified into paraffins and nonparaffins (fatty acids and sugar alcohols) [15–17].

The paraffins [18–21] are by-products of petroleum distillation. They are a mixture of alkanes from C1 to C24. They are molecules of formula CnH2n + 2 and structural formula CH3-(CH2)n-CH3. The paraffins between C5 and C15 are liquids and the rest are waxy solids. An important property of paraffins is that the longer the carbon chain, the higher the melting temperature. Paraffins are nontoxic, chemically stable, and inert below 500°C. Table 2 shows the thermophysical properties of some paraffins.

Table 2. Thermophysical properties of some paraffins.

PCMChemical compositionTmeltingkPCMLf
°CW/(m K)kJ/kg
n-Hexadecane [22,23]C16H3418.00.2210–238
n-Heptadecane [22,23]C17H3619.00.2240
Paraffin [24]C16  C1820.0152
Paraffin [4,24]C1721.7213
Paraffin [4,24]C1890-0.2189
n-Octadecane [18,22,23]C18H3828.00.15200–245
n-Nonadecane [18,22,23]C19H4028.00.36245–250
n-Eicosane [18,22,23]C20H4236247.0
n-Henelcosane [18,22,23]C21H4439.00.15201.0
Eutectic PCM

A eutectic PCM is a mixture of two or more pure substances that melts and crystallizes at a constant temperature, unlike the usual mixtures. Eutectics behave like pure bodies from the point of view of phase change. This type of PCMs can be classified into three subfamilies: mixtures of organic materials, inorganic materials, and organic-inorganic mixtures. Table 3 shows the melting temperature and latent heat of some eutectic PCMs.

Table 3. Thermophysical properties of some eutectic PCMs.

PCMTmeltingLf
°CkJ/kg
45 % CaCl2 · 6H2O + 55 % CaBr2 · 6H2O [5]14.7140
66.6 % CaCl2 · 6H2O + 33.3 % MgCl2 · 6H2O [25]25127
48 % CaCl2 + 4.3 % NaCl + 0.4 % KCl + 47.3 % H2O [25]27188
40 % CH3COONa · 3H2O + 60 % NH2CONH2 [5]30200.5
61.5 % Mg(NO3)2 · 6H2O + 38.5 % NH4NO3 [25]52125
53 % Mg(NO3)2 · 6H2O + 47 % Al(NO3)2 · 9H2O [25]61148
59 % Mg(NO3)2 · 6H2O + 41 % MgBr2 · 6H2O [25]66168
14 % LiNO3 + 86 % Mg(NO3)2 · 6H2O [25]72180
66.6 % urea + 33.4 % NH4Br [25]76161

Table 4 summarizes the advantages and disadvantages of the different PCMs.

Table 4. Advantages and disadvantages of different PCMs.

Empty CellAdvantagesDisadvantages
Organic

Availability in a wide range of temperatures

No phase segregation

Chemical stability

Undercooling is negligible

Compatibility with building materials

Ecological sobriety

100% recyclables

Low latent heat

Low thermal conductivity

High volume expansion

Flammable

High cost compared to hydrated salts

Inorganic

High heat of melting

Availability

High thermal conductivity

Low volume expansion

Cheap

Not flammable

Segregation

Loss of efficiency due to melting/solidification cycles

Supercooling

Corrosivity

Dehydration due to thermal cycles

Eutectic

Volumetric storage density is slightly higher than organic PCM

They have a net melting point similar to a pure substance

Only limited data are available on the thermodynamic properties

The use of these materials is very recent for the application of thermal storage

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Simulations of 3D inhomogeneous temperature distributions in Li-ion pouch cells with passive thermal management

Silven Stallard, Xianglin Li, in Handbook of Thermal Management Systems, 2023

3.3 Varying PCM properties

PCM is an extremely valuable and highly researched tool [21], especially in the application of passive thermal management. Their high latent heat, or heat of fusion, values are one of their main advantages in this application, allowing them to absorb substantial amounts of heat while never leaving their melting temperature. One of the PCMs main disadvantages is their relatively low thermal conductivity values. This study investigates how changing these property values affects the thermal behavior of the PCM as a thermal management material. The exact values for the high and low latent heat and thermal conductivity are listed in Table 4.

Table 4. Properties used in PCM [22,23] study to develop trends of thermal conductivity and latent heat in the thermal behavior of the battery.

PropertyStandardHighLHMidLHLowLHHighTCLowTC
Thermal conductivity [W/m/K]0.358 (s)
0.148 (l)
0.358 (s)
0.148 (l)
0.358 (s)
0.148 (l)
0.358 (s)
0.148 (l)
1.088 (s)
0.148 (l)
0.148 (s)
0.148 (l)
Latent heat [kJ/kg]20030015090200200

Properties are listed under the names of the tests in Fig. 9.

Their values were chosen to reflect the reasonable extremes that could be found among various types of PCM currently available [8,10,22–25]. This resulted in a rough range of 90–300 kJ/kg and 0.148–1.088 W/m/K for the latent heat and thermal conductivity values. No other properties of the PCM were altered during these tests. The temperatures of the battery surface were monitored and recorded for the trial cases and are shown in Fig. 9.

Fig. 9

Fig. 9. Effects of varying the latent heat and thermal conductivity on the temperature distribution on the surface of the battery, where (A) shows the average surface temperature of the battery, and (B) shows the maximum temperature difference on that surface.

The varying of the latent heat and thermal conductivity of the PCM had a limited effect on the temperature of the battery during discharge, as shown in Fig. 9. The range of thermal conductivity and latent heat found in currently applied PCM types is not significant enough to distinguish the performance of the high and low latent heat and thermal conductivity trials from each other.

This is evidence that a different alteration is needed to improve the performance of PCM [6,25]. Porous media fills this role as a thermal conductivity aid and has been shown to drastically improve PCM performance.

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Solar Water Heaters

Zhangyuan Wang, ... Xudong Zhao, in A Comprehensive Guide to Solar Energy Systems, 2018

6.4.1 SWHs With Phase Change Materials

PCM, also called latent heat storage material, has a high capability of storing and releasing large amount of heat within a constant or a narrow temperature range [1,18,19]. Two properties that make PCMs attractive in SWH systems are: their compactness and also their small volume change during a phase change [20–22]. The SWH systems, which include PCMs, can be divided into two types: those where the PCM is directly linked to the solar collector and those where the storage unit is filled with the PCM.

A schematic diagram of a flat-plate solar collector involving a PCM is given in Fig. 6.7. The impure PCM surrounds the solar collector tubes and is covered with black absorber [23]. Typically the system can maintain an operating temperature of the collector of under 40°C for 80 min with a constant solar radiation of 1000 Wm−2 [22]. Such systems have been shown to have efficiencies of between 42% and 55% higher than that of conventional SWH systems [24].

Figure 6.7. Schematic of the flat-plate solar collector with PCM [23].

PCM, phase change material.

A refined version of this type of SWH system was investigated by Chen et al. [25] (Fig. 6.8) and has the tubes of the flat-plate solar collector embedded within a high porous aluminum foam incorporating paraffin. They found that the performance of the system was improved significantly compared with the paraffin system without aluminum foam as can be seen in Figs. 6.9 and 6.10 [25].

Figure 6.8. Schematic of the solar collector with high porous aluminium foam incorporating with paraffin [25].

Figure 6.9. Variations of the temperatures of the paraffin and aluminium foams in solar collector [25].

Figure 6.10. Variations of the heat loss coefficient of the collector [25].

SWH systems involving PCMs in the storage unit have been investigated by Tarhan et al. [26]. The PCMs they used were lauric acid and myristic acid. The results showed that the lauric acid storage could retain a stable water temperature, and the myristic acid storage could reduce the heat losses during night.

Fazilati and Alemrajabi [21] investigated the performance of a solar water heater using paraffin wax in spherical capsules as the storage medium in the jacketed shell type tank. It was evaluated that 25% of service time of the SWH system could be prolonged by using PCMs.

A SWH system with a galvanized steel storage tank containing paraffin was investigated by Al-Hinti et al. [27] (Fig. 6.11). The total volume of the storage tank was at 107.4 L with paraffin occupying 49.4 L and the water encapsulated making up the remaining volume (58 L). This water-paraffin PCM storage system reached a temperature of 45°C higher than the ambient temperature after 24 h of operation.

Figure 6.11. Schematic of the SWH system with water-PCM storage [27].

PCM, phase change material.

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Battery thermal management through simulation and experiment: Air cooling and enhancement

Seham Shahid, Martin Agelin-Chaab, in Handbook of Thermal Management Systems, 2023

2.4.2 PCM-based BTMS

The PCM material is used to extract heat from the cells through its latent heat. The method was first suggested by Al Hallaj and Selman [50]. The effects of PCM were studied by Javani et al. [51], and over a battery submodule, a high-temperature uniformity was attained, and the PCM was capable of keeping the cell temperature within safe operating ranges. Jiang et al. [52] studied the effects of composite PCM by combining expanded graphite with paraffin. During the discharge process of 5C, the temperature was maintained at <44°C and temperature uniformity to <2°C. An experimental study by He et al. [53] found that the optimum percentage of expanded graphite in a paraffin mixture was 7%. A novel PCM was developed by Hussain et al. [54]. Compared to pure paraffin, the thermal conductivity of this graphene-coated nickel foam saturated with paraffin PCM was increased by 23 times, and the thermal performance of the BTMS increased by 17%.

However, to improve the overall heat transfer coefficient of a PCM-based BTMS, a secondary thermal management strategy is required to extract the heat away from the PCM when the latent heat removal capability is completely consumed. This then results in increased complexity of the overall BTMS.

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Solar panel cooling using hybrid cooling systems

Gökhan Yıldız, ... Muhammet Kayfeci, in Handbook of Thermal Management Systems, 2023

4 Nanoparticle + PCM

Nanoparticle and PCM are cooling methods used separately in PVT panels. However, these cooling techniques are used as hybrids in different combinations. These are nanofluid-PCM, fluid-nano-PCM, and nanofluid-nano-PCM.

Since PCMs are materials with low thermal conductivity, their use is low. Therefore, dispersing high conductivity materials into PCM is one of the best solutions for improving performance. Scientists proved that the homogeneous dispersion of nanoparticles in PCMs leads to high heat transfer and thermal conductivity [29]. The preparation stage is as important as the use of nano-PCMs. There are many techniques used for the nano-PCMs’ preparation. Generally, one-step and two-step methods are used to prepare nano-PCM. The one-step or two-step method is a combined method of producing and dispersing the nanoparticle simultaneously. The most popular method for the nano-PCM’s preparation is the hot evaporation method. This method used in the nano-PCM’s preparation is a two-step method. In the two-step method, nanoparticles, nanofibers, chemical, or physical processes prepare nanotubes. The nanoparticles and liquid PCM are blended with the aid of high shear mixing and homogenization. This method is more economical and nano-PCM can be produced on a large scale [30,31]. Researchers have obtained high quality nano-PCM using the two-step method commonly (Fig. 4).

Fig. 4

Fig. 4. One-step and two-step method for preparation of nano-PCM [6].

Another method used to obtain nano-PCM is mixing and sonication. The specified nanoparticles’ amount is added to the liquid PCM and mixed using a magnetic stirrer for approximately 1 h. After mixing the nano-PCM, it is sonicated for approximately 30 min in the frequency range of 45–65 Hz and allowed to cool. During the sonication process, the temperature must be above the melting temperature of the PCM [32]. The steps of the mixing and sonication method are given schematically in Fig. 5.

Fig. 5

Fig. 5. Schematic diagram of preparation of nanofluids [6].

Another method used in nano-PCM preparation is sonication and ultrasonication. The specified amount of nanoparticles is added directly to the liquid PCM and sonicated at a frequency of 45–60 Hz for about 30 min. The nanoparticle is kept in an ultrasonic bath for 2 h until it is completely homogeneously dispersed in the PCM. During the ultrasonication process, the bath temperature must be higher than the melting temperature of the PCM [33,34].

There are many studies by researchers related to different nanoparticle-PCM hybrid cooling methods. These studies are summarized and detailed in Table 2.

Table 2. Studies of nanoparticle-PCM hybrid cooling techniques.

AuthorsCoolant typePCMNanoparticlesElectrical efficiencyThermal efficiencyRemarks
PVT-nano-PCM
Ma et al. [35]Paraffin (44°C)AirCuN/A86.5%There was an 8.3% increase in the stored heat in nano-PCM compared to PCM
Sharma et al. [36]AirRT 42 (42°C)CuO (60 nm)N/AN/AIn the finned plate PVT module with nano-PCM, a decrease of 12.5°C was observed in the PV module surface temperature
Mousavi et al. [37]WaterParaffin C18 (29°C), Paraffin C22 (44°C), Paraffin C15 (14°C), Palmitic/capric acid (17.7–22.8°C) and sodium phosphate salt (37°C)Copper foam14.5%86%Higher thermal energy in paraffin C22 and higher electrical efficiency in sodium phosphate salt and the flow rate of the PV module is 0.028 kg/s
Salem et al. [38]WaterCalcium chloride hexa hydrate (31°C)Al2O3 (40 nm)13.3%68%The exergy efficiency was calculated as 13.6%. Higher electrical, thermal, exergy efficiency and lower surface temperature were obtained in Al2O3-PCM
Nanofluid-based PVT-PCM
Sardarabadi et al. [39]WaterParaffin (42°C)ZnO (35–45 nm)13%46%PVT module with nanofluid-PCM has higher thermal, electrical and total efficiency. A greater decrease in PV module surface temperature was obtained
Hosseinzadeh et al. [40]WaterParaffin (46–48°C)ZnO (35–45 nm)14.05%51.66%Nanofluid-PCM has higher total, thermal and exergy efficiency than PV and nanofluid based PVT module
Lari and Sahin [41]WaterOctadecane (28°C)Ag11.7%27.3%The system can meet 77% electrical power and 27.3% thermal power of residential demand
Hassan et al. [42]WaterRT 35HC (35°C)Graphene14%45.8%Higher performance was obtained in the PVT module with nanofluid-PCM at 0.1% vol. and 40 L/min. The decrease in PV module surface temperature was 23.9°C
Nanofluid-based PVT-nano-PCM
Al-Waeli et al. [33]WaterParaffin (49°C)SiC (45–65 nm)13.7%72%The electrical, thermal and overall efficiency is improved in the PVT module with nanofluid-nano-PCM. The PV module surface temperature has been reduced to 30°C.
Sarafraz et al. [43]Water-EG (50:50)Paraffin (49°C)MWCNT276.3 W/m2307.9 W/m2Higher electrical and thermal efficiency at 0.2% fraction was obtained in the PVT module with nanofluid-nano-PCM.
Al-Waeli et al. [44]WaterParaffin (40°C)SiC13.7%71.2%The overall performance of the PVT module with nanofluid-nano-PCM was 85.7%.
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Futuristic methods of electronics cooling

Ali Uysal, ... Muhammet Kayfeci, in Handbook of Thermal Management Systems, 2023

2.5 Phase change material-based cooling

Phase change materials are mostly used between high-performance microprocessor and heat sink. They are solid at room temperatures. However, after phase change or reaching melting temperature, they behave like thermal adhesive or grease and turn into liquid, their viscosity decreases rapidly and they flow toward air spaces. This process requires around 0.1 bar of pressure to bring the two surfaces together. This process continues until the two surfaces come into contact at a minimum of three points, or the flow stops when the gap becomes a very thin layer. These materials do not provide electrical insulation because they allow two surfaces to make contact. Four categories of solid-liquid PCMs with melting temperatures in the range from 40 to 120°C are shown in Table 1.

Table 1. Thermo-physical properties of common phase change materials [39].

Empty CellOrganic paraffinOrganic non-paraffinInorganic salt hydratesInorganic metal eutectics
Melting temp. (°C)−12 to 187&lt;15020–14030–125
Latent heat (J/m3) × 106190–240140–430250– 660300–800
Density (kg/m3)∼810900–1800900–2200−8000
Thermal conductivity (W/m °C)∼0.250.20.6–1.2∼20
ToxicityNoSome areHighlySome are
CorrosionLowSome areHighlySome are
Congruent meltYesSome doMost do notYes
SupercoolNoNoMost doNo

Recently, many researchers have extensively studied the characteristics of phase change materials to improve performance in electronic device cooling applications (Fig. 14). N-eciosene and tricosene are the most used phase change materials [40–43]. Weng et al. [44] experimentally investigated the thermal performance of a heat pipe with phase change material for electronic cooling.

Fig. 14

Fig. 14. Classification of phase change material.

Experimental studies were carried out to obtain the system temperature distribution from charge, discharge, and simultaneous charge/discharge performance tests. Three different phase change materials in different volumes were used in the study. The cooling module with tricosene as phase change material was found to save 46% fan power consumption compared to the traditional heat pipe. Fok et al. [45] used the phase change material-based cooling method in their experimental study for the cooling of handheld electronic devices. As the phase change material, n-eicosone material placed in the heat well with finned and finless surfaces was used. In the study, the effects of phase change material, number of fins, device orientation, and power level (ranging between 3 and 5 W) on thermal performance underweight and light usage conditions were investigated.

To capture casual energy spikes getting out of active components, PCM can be used as shown in Fig. 15. When the melting point of the PCM is chosen correctly, it freezes during the periods of low energy usage and melts during the periods of high energy usage. The final outcome is that the maximum temperature continued around a specific value, near the PCM’s melting temperature.

Fig. 15

Fig. 15. Device power vs time plot.

Ever since mobile devices such as tablets and smartphones were invented, there has been a lot of talk about regulating temperature fluctuations in these devices. However, such a device using PCM is not known. The main difficulty is space. On the other hand, it is hard to give space even the very thin heat emitters. The most considered PCM for these applications is paraffin, but it has low latency. The meaningful effect of the PCM on the smartphone requires at least a thickness of the order of 1 mm. Considering that thinness is one of the important features of a phone and the total thickness is 7 mm, it is seen that the required paraffin thickness is high. Other materials such as salt hydrates are too dangerous for such applications due to their undesired chemical properties (toxicity, corrosiveness, etc.).

If material is developed in the future, PCMs may find large usage in mobile applications. However, for now, their usage is limited to mobile devices, where thickness is not as important. Expert thermal consultants and thermal engineers should carefully perform any consideration of PCM for mobile devices or as part of solutions for electronics cooling.

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