Composite Phase Change Materials Research Articles

Thermal Management System with Intrinsically High Thermal Conductive and Antileakage Composite Phase-Change Materials for Battery Module

Thermal Management System with Intrinsically High Thermal Conductive and Antileakage Composite Phase-Change Materials for Battery Module

Preparation and thermal conductivity enhancement of binary non-eutectic phase change materials based on alum-urea for solar heat storage system

Heat accumulators using latent heat storage are commonly used in solar energy storage systems. Potassium aluminum sulfate dodecahydrate (Alum) is an inexpensive phase change material, but the high phase change temperature limits its application in heat accumulator. To address this limitation is controlling the melting temperature of Alum. In this study, Alum-urea mixtures were first developed by adding 10 wt% urea. Modified phase change materials (MPCM) without phase separation and supercooling were developed by adding NiSO4·6H2O and xanthan gum to the Alum-urea mixture. Composite phase change materials (CPCM) with high thermal conductivity were developed by loading MPCM in expanded graphite. The melting temperature of the Alum-urea mixture was 72.52 °C with 10 wt% urea content, which was 21.4% lower compared to the Alum. The MPCM still has a high phase change enthalpy (157.7 J·g−1) and ignorable subcooling degree (0.8 °C). The thermal conductivity of CPCM is increased by 16 times, and it has good photothermal conversion ability. The CPCM holds significant promise for applications in latent heat energy storage.

The effect of heat flux on enhancement heat transfer mechanism in copper metal foam composite paraffin wax during melting process: Experimental and simulation research

To investigate the effect of heat flux on the enhanced heat transfer in phase change materials (PCMs) composed of copper metal foam (CMF) and paraffin wax (PX), a semi-cylindrical visualized heat storage device with a varied heat flux of 7.3 kW/m2, 8.5 kW/m2, 9.7 kW/m2, and 10.9 kW/m2 was established in this paper. Moreover, a 3-D mathematical model of composite phase change materials (CPCMs) was established using hybrid grid to study the temperature distribution, imbalance effect, flow, heat transfer mechanisms, and heat storage performance during the melting process. The results showed that the melting time of the CPCMs decreased as the heat flux increased. Compared with a heat flux of 7.3 kW/m2, the melting time was shortened by 10.05 %, 20.71 %, and 27.21 %, respectively. In addition, the Rayleigh number (Ra) increased with the increase in heat flux, and the amplitudes of Ra were 1.45×108,1.54×108,1.61×108, and 1.74×108, respectively, which indicated that the higher the heat flux, the larger the amplitudes. Moreover, the heat transfer mechanism during the melting process was dominated by conduction; however, with the increase in heat flux, the maximum flow velocity of the liquid paraffin increased, which caused the proportion of natural convection to increase from 27.80 % to 31.30 %. Hence, the integrated heat transfer coefficient of CPCMs increased from 5.69 W/(m·K) to 5.81 W/(m·K). However, the temperature imbalance effect of the CPCMs was exacerbated, as evidenced by the increased maximum temperature difference in the vertical direction of the center of the CPCMs from 24.7 K to 35.6 K. Besides, the heat storage performance was enhanced. Compared with a heat flux of 7.3 kW/m2, the heat storage capacities of the CPCMs increased by 4.21%, 9.46%, and 12.66 % with increasing heat flux, and the heat storage rates of the CPCMs increased by 15.3 %, 34.9 %, and 52.3 %, respectively. Furthermore, the relative error of the overall melting time was 3.4 %, indicating that the model provided reasonable predictions.

Preparation and performance analysis of polyethylene glycol/epoxy resin composite phase change material

It is crucial for their widespread application to develop phase change materials (PCMs) that can be mass-produced and possess high thermal storage capacity and stability. This study uses polyethylene glycol (PEG) as the phase change material and epoxy resin as the matrix to prepare polyethylene glycol/epoxy resin composite phase change materials (EPPCM) by blending and analyzing the effects of PEG's molecular weight and content on EPPCM's performance. The results indicate that PEG and epoxy resin are physically blended without chemical reaction. When the molecular weight of PEG is fixed, the larger the content of PEG, the higher the crystallinity, phase change enthalpy value, and phase change temperature of EPPCM, and the weaker the thermal cyclic stability and mechanical properties. When the content of PEG is fixed, the larger the molecular weight of PEG, the higher the crystallinity, phase change enthalpy value, and phase change temperature of EPPCM, the stronger the thermal cyclic stability, and the weaker the mechanical properties. Using PEG-10000 as the PCM with a PEG to epoxy resin ratio of 1:2.5, the EPPCM shows a phase change exothermic temperature range of 33.4 °C to 45.7 °C, an endothermic temperature range of 54.3 °C to 65.4 °C, a phase change enthalpy of 130.0 J/g, and only 1.56 % mass loss after 30 phase change cycles.

Form-stable oleic acid based polyHIPE/nanoclay framework supported composite phase change materials for low‐temperature latent heat storage

Latent heat storage, one of the promising methods in energy storage, is an important option for the sustainable use of energy and is attracting more attention day by day. Phase change materials (PCMs) produced for this purpose allow the storage/release of latent heat due to the temperature of the medium and can be obtained using various methods. In this work, the preparation of a new fatty acid based composite phase change material was accomplished by applying simple two-step approach. Here, oleic acid (OA) was employed as PCM, and emulsion templated macroporous polymers (polyHIPEs) as supporting matrices. Furthermore, macroporous supports were also fabricated in the presence of surface modified montmorillonite nanoclay to enhance thermal properties of the targeted composite PCMs. In this respect, a neat macroporous support and surface modified nanoclay enhanced macroporous support were synthesized. Then, the composite PCMs were prepared by filling the macropores of the obtained polymer foams with OA via a solvent-assisted impregnation approach for cold energy storage. The examinations on the thermal characteristics of the composite PCMs were performed through Differential Scanning Calorimetry (DSC), while the chemical structure was analyzed with FT-IR. Besides, polarizing optical microscopy (POM) was used to monitor the loading of OA to macroporous polymer supports. Additionally, the thermal behaviors of composite PCMs were investigated by the temperature-history (T-history) method and the findings were also found to be compatible with DSC. Furthermore, thermal stability of the composite PCMs was investigated through thermogravimetric analysis (TGA). According to DSC results, the prepared composite PCMs are candidates for utilizing cold thermal energy storage such as building cooling, cold protection and cold chain transportation applications with their proper melting temperatures (7.08 °C and 7.40 °C) and moderate latent heat capacities.

Thermal management of PV based on latent energy storage of composite phase change material: A system-level analysis with pore-scale model

Perovskite Solar Cell (PSC) have recently emerged as exciting new candidates of Photovatics (PVs) for solar-to-electrical energy conversion. Nevertheless, one huge obstacle to its commercialization is how to improve its tolerance to operation at elevated temperatures. To address this issue, Composite Phase Change Material (CPCM) incorporated with a porous skeleton structure is proposed to integrate with PVs. In this structure, an important theoretical problem is that the temperature dependence of PV and the temperature control behavior of CPCMs interact with each other (bidirectional relationship). In this work, a pore-scale lattice Boltzmann phase change model is established to describe the dynamic thermal behavior of CPCMs and explore the roles of the bidirectional relationship between PVs and CPCMs, the change of power conversion efficiency influenced by temperature variation and glass transmissivity is discussed by comparing the overall liquid fraction of CPCMs, and the average temperature and power conversion efficiency of PVs. Furthermore, the situation of time-varying solar irradiation is discussed to mimic real application conditions. Results indicate that the neglecting temperature dependency of PVs leads to underestimation of PV surface temperatures and overestimation of power conversion efficiencies, while glass transmissivity provides reverse effects. These phenomena not only happen in constant solar irradiation but also in varying solar irradiation, calling for increasing attention to designing PV/CPCMs for varying heat flux conditions. The findings of this work establish a comprehensive manner toward integrated design of CPCMs for PV thermal control.

Production and assessment of UV-cured resin coated stearyl alcohol/expanded graphite as novel shape-stable composite phase change material for thermal energy storage

Expanded graphite-phase change materials (PCM) structures are reinforced to polymers with various methods to fabricate advanced thermal energy storage materials. However, these methods still suffer from processing time and product efficiency challenges. In this study, the UV-curing method was used to produce shape-stable EG-PCM-reinforced resin composites with fast curing and low process temperature of the resin. The composite material, comprising UV-curable resin (30 %), stearyl alcohol (65 %), and Expanded graphite (5 %), was synthesized. This synthesis aimed to address the limitations of traditional PCMs, such as low thermal conductivity and leakage. Differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) were used to characterize the materials' phase change behavior and thermal stability. Scanning electron microscopy (SEM) and Fourier-transform infrared spectroscopy (FTIR) analyses were conducted to elucidate the microstructure and crystallinity of composite materials. The composites, exhibiting near-perfect impermeability with leakage as minimal as 0.89 %, not only enable the attainment of cooler environments by 2–3 °C under hot air conditions but also demonstrate exceptional thermal stability up to 207 °C, as evidenced by TGA results. Additionally, they offer a remarkable melting enthalpy value of 153.1 J/g. These composites, with their shape-retention ability during phase transitions and high thermal energy storage capacity, are a versatile and efficient option for sustainable energy management. This research contributes to the development of innovative materials for renewable energy integration and reducing carbon emissions.

A polyurethane solid–solid phase change material for flexible use in thermal management

Phase change materials (PCMs) have received great attention in thermal management of electronic devices due to their high energy storage density and no need for additional energy supply. Yet the leakage problem after phase change limits their application greatly. In this paper, the block copolymerization was used to prepare a novel solid–solid phase change material (SSPCM) with a melting enthalpy of 90.26 J/g, starting pyrolysis at a temperature of more than 300 °C, and its physicochemical and thermal properties remained basically unchanged after 100 heating/cooling cycles. Notably, this SSPCM has excellent shape stability and can be pressed into phase change film with flexibility, thermally induced self-healing capability and recyclability. Finally, we innovatively combined this SSPCM, copper foam (CF), and polyimide tape (PI) to obtain a composite phase change material (CPCM) with both high thermal conductivity (1.1994 W/m·K) and high electrical insulating properties. Thermal management experiment shows that this CPCM has good thermal management performance and can significantly reduce the temperature rise rate of the simulated CPU. The SSPCM prepared in this study shows great potential for application in thermal management of portable electronic devices and flexible wearable electronic devices.

A polyurethane solid-solid composite phase change material based on modified graphene oxide for efficient thermal management

Solid-solid phase change materials (SSPCMs) are potential materials for energy storage and thermal management, and improving mechanical property and heat transfer performance is the key to practical application. After modified graphene oxide (TGO) was prepared by toluene diisocyanate, a kind of super-tough, form-stable and leak-proof polyurethane composite phase change material (PU-TGO) was constructed by the two-step polymerization of isophorone diisocyanate and 1, 4-butanediol using polyethylene glycol and TGO. TGO has more uniform and stable dispersion than traditional graphene oxide, and its chemical crosslinking with polyurethane phase change materials makes the composite have better shape stability, mechanical strength, thermal conductivity and flexibility. PU-TGO has thermal conductivity and elongation at break up to 0.3072 W/(m•K) and 540%, respectively, and maintains excellent thermal stability and 72.09 J/g enthalpy after 500 thermal cycles. PU-TGO prepared by chemical crosslinks in this paper further demonstrates the great potential of phase change materials in the field of thermal management of new electronic devices.

Study on the melting characteristics of composite phase change materials and the power generation performance of coupled thermoelectric systems under supergravity conditions

Miniaturization and integration of electronic equipment in aircraft have resulted in a substantial increase in thermal load. However, aircraft often experience acceleration maneuvering flights in supergravity environments, which makes comprehensive research on thermal management under supergravity conditions necessary. The influence of gravity on the thermal storage properties of composite phase change materials doped with graphene nanoparticles (GNP-PCM) was investigated in this study by simulation. Under 2g, 4g, 6g, 8g, and 10g gravity conditions, the melting time is reduced by 14.86%, 27.05%, 33.31%, 37.00%, and 39.79%, respectively, compared with normal gravity conditions. Moreover, the integration of the PCM with a thermoelectric power system facilitated waste heat utilization. Incorporating GNPs markedly enhances power generation efficiency under 10g supergravity conditions. With an open-circuit voltage of 0.8 V and a maximum output power of 0.11 W, the power generation reached 81.62 J, which is 53.91% higher than that of pure PCM. This enhancement can be attributed to the improved natural convection and accelerated melting rate facilitated by the GNPs. This study elucidates the underlying physical mechanisms affecting the melting rate of PCM under increased gravity conditions. Furthermore, coupling PCM with a thermal power generation system provides a rational approach for the reuse of waste heat.

A novel cement mortar comprising natural zeolite/dodecyl alcohol shape stable composite phase change material for energy effective buildings

Investigations into Phase Change Materials (PCMs) for heat storage in facilities have gained significance, contributing to indoor temperature regulation, decreased energy usage, and improved building efficiency, thereby supporting sustainability initiatives. However, the issue of PCM leakage during the heating phase has constrained its thermal energy storage (TES) prospective at large scaled-practices. Addressing this concern, the present study emphases on elimination of the leakage problem of dodecyl alcohol (DA) as a PCM with appropriate melting temperature for building TES request by its impregnating into the natural zeolite (NZ) as a low cost host matrix. In the second stage of the work, using the developed shape stable-NZ/DA (SS-NZ/DA) composite PCM in cement mortar instead of sand, novel cementitious mortars with enhanced thermal properties were created by incorporating different weight percentages (25 %, 50 %, 75 %, and 100 %) compared to the mortar comprising NZ. Experimental works were carried out to analyze the shape-stability, TES features, cycling TES stability and thermal endurance of the SS-NZ/DA composite as well the physical properties, mechanical strength, and solar temperature regulation performance of the SS-NZ/DA included mortars. The SS-NZ/DA demonstrated the melting enthalpy of 107.5 J/g at 19.47 °C and a freezing enthalpy of 106.1 J/g at 19.86 °C. The performance test results obtained under real weather conditions indicated that the integration of SS-NZ/DA into mortar presented maximum drop of 10 % and 9.26 % in peak indoor temperature at the SS-CPCM slab surface and the center of SS-CPCM slab-cabin, respectively, accompanied by an approximate 3-hour time delay. Mortars with SS-NZ/DA composite PCM exhibited a decreased dry unit weight (1189 kg/m3) and thermal conductivity (0.394 W/mK) while experiencing a moderate strength loss (4.5 MPa). These favorable physico-mechanical properties, TES characteristics and thermal management capability make the novel cementitious mortar containing composite PCM as an energy-efficient material for creating thermo-regulative building components. In this study, the natural, economical, and environmentally friendly nature of the NZ material used for PCM impregnation, its ability to contain a high percentage of PCM (up to 45 %) without any leakage issues, is the most fundamental and important characteristic of the composite used. The most unique feature of this composite mortar is the ability to achieve sufficient mechanical and thermal properties in cementitious mortars produced using this composite material without any leakage problems.

Enhancing sustainability with waste hemp-shive and phase change material: Novel gypsum-based composites with advanced thermal energy storage properties

This study addresses the rising demand for sustainable construction by introducing composite materials from natural and renewable resources: gypsum, hemp, and phase change materials (PCMs). These materials cater to the growing preference for eco-friendly building solutions. Incorporating hemp enhances sustainability while integrating PCMs into the porous hemp structure ensures adequate thermal energy storage and release without leakage. Firstly, the agricultural waste hemp shives and lauryl alcohol (LA) PCM were mixed to create shape-stabilized hemp/PCM composites. The highest PCM ratio was determined in shape-stabilized composites exhibiting non-leakage properties, which was 45 wt %. These composites were then incorporated into gypsum materials at loadings of 7.5 %, 15 %, 22.5 %, and 35 wt % to produce the final composites. Morphological, thermal, and chemical characteristics of shape-stabilized composites were examined using SEM, TGA, and DSC, while the solar thermoregulation tests assessed the gypsum matrix composites. The phase change temperature of PCM was determined as 20.24 °C with a melting enthalpy value of 224.4 J/g. The hemp/PCM shape-stabilized composites demonstrated an impressive melting enthalpy value of 100.2 J/g, with only a slight reduction to 99.5 J/g after 750 test cycles. When the ambient temperature exceeded 50 °C, the central temperature of the cabins containing PCM composites was found to be at least 4 °C cooler than those containing only gypsum. Conversely, when the ambient temperature dropped to around 20 °C, it was observed that the central temperature of the cabins with PCM composites was approximately 2 °C warmer than those with only gypsum. This study introduces a novel approach to creating environmentally friendly gypsum/hemp/PCM composites for thermal energy storage systems.

Bidirectional anisotropic bacterial cellulose/polyvinyl alcohol/MXene aerogel phase change composites for photothermal conversion enhancement

The issues of inherent low thermal conductivity, slow heat transport rate and easy leakage are critical challenges for accelerating solar-thermal energy harvesting and storage for organic solid-liquid phase change materials (PCMs). Aerogel carriers with thermal conductivity enhancement based on ice temple methods show favorable potential for PCMs solar thermal applications. Comparing with disordered and unidirectional freezing, bidirectional freezing can assemble efficiently in multiple dimensions and result in long-range ordered structures. In this paper, bacterial cellulose/polyvinyl alcohol/MXene aerogels were constructed by bidirectional freezing. The anisotropic PCMs composites were from vacuum impregnation PEG into aerogel networks. By controlling crystallization and growth of ice crystals through the dual temperature gradients, the PCMs composites obtained enhanced heat transfer efficiency in horizontal and vertical directions. Bidirectional aligned PCMs with PDMS wedge angle of 0° and 20° exhibit high thermal conductivity of 0.716 W m−1 K−1 and 0.768 W m−1 K−1, which were 184% higher than that of PEG, and photothermal conversion efficiency of 55.17% and 76.91%. Remarkably, the PCMs composites with a 20° PDMS wedge angle also exhibited a high PCM loading capacity (96.3%) and a high enthalpy (157.7 J/g). The results show that bidirectional anisotropic PCMs composites have excellent overall performance and are expected to improve solar thermal application.

Preparation and characterization of phase change erythritol/expanded graphite@Ag composite materials for thermal energy storage

In this paper, the composite PCMs of Erythritol (ET)/Expanded Graphite (EG)@Ag were prepared by vacuum impregnation method with EG@Ag as matrix and the ET as the phase change material (PCM). The chemical compatibility, thermodynamic properties and thermal stability of composite phase change materials (CPCMs) were systematically examined. The results illustrated that the CPCMs possessed good chemical compatibility with only physical interaction between ET and EG@Ag. The supercooling of ET/EG@Ag-8 wt% reduced by 42.13 °C, which also remain high melting and solidification enthalpy of −258.09 J/g and 187.63 J/g, respectively. The thermal conductivity of ET/EG@Ag-8 wt% reached to 2.87 W/(m·K), which resulted in an enhancement of 463 % in the thermal conductivity of ET. Thermal stability results show that all CPCMs of ET/EG@Ag present good thermal stability below 200 °C. This offers new prospects for the use of ET in the field of medium temperature phase transitions.

Preparation and characteristic of palmitic acid/flower-shaped CuS composite phase change material for effective heat storage and photothermal conversion

Designing and synthesizing the excellent heat storage and photothermal integrated composite phase change materials (PCMs) is an effective strategy for solar energy utilization. This work focuses on two kinds of CuS (cuboidal and 3D flower-shaped) with different morphology were designed as substrates and photothermal materials, and PA/F–CuS and PA/C–CuS composite PCMs have been prepared by melt-blending and vacuum impregnation method. Through SEM and pore structure characterization as well as leakage testing, it is proved that 3D layered flower-shaped CuS not only exposes the large specific surface area and rich adsorption sites, but also 2D thin layers can perform multiple reflections to improve the utilization rate of solar energy. The flower-shaped CuS is more suitable for the supporting material. Noteworthy, the latent heat of PA/F–CuS can reach 226.3 J/g, and the thermal conductivity is 0.3447 W/(m·K). Furthermore, compared with pure PA, the photothermal property of PA/F–CuS increased by 49.22–84.59%, and the photothermal conversion efficiency can reach 70.3%. This work provides an innovative idea for the design and manufacture of composite PCMs related to medium and low temperature solar energy storage, and has broad application potential in the field of thermal energy storage such as solar energy utilization and building insulation materials.

Experimental study on the thermal response of a metal foam dual phase change unit thermal storage tank

Adding fins or metal foam to phase change units can effectively enhance the heat storage efficiency of thermal energy storage (TES) tanks, thereby improving the reliability of TES tanks in coordinating renewable energy supply and demand. In this study, an experimental TES tank platform was designed and constructed to investigate how the addition of straight fins, metal foam, and straight fin/metal foam composite materials to paraffin affects the temperature response during the heat storage process. High-temperature water was selected as the heat transfer fluid (HTF) and injected from the top into the TES tank at the same paraffin fill level, and T-type thermocouples were arranged along the central axis of the phase change unit. TES tanks filled with either pure paraffin or composite phase change materials were tested by varying the HTF inlet temperature and velocity, and temperature response data were captured and recorded using a KEYSIGHT DAQ970A data logger. The results indicated that increasing the HTF inlet temperature significantly enhanced the heat storage rate while increasing the HTF inlet velocity had varying effects on different phase change units. A comprehensive analysis suggested that an inlet velocity of 1.3 m3/h (from a range of 0.8–1.8 m3/h) was reasonable. The addition of enhancement measures improved the temperature drift phenomena and effectively increased the temperature response rates and distribution uniformity. Moreover, the straight fin/metal foam composite material exhibited the best performance.

Carbonized-wood based composite phase change materials loaded with alumina nanoparticles for photo-thermal conversion and energy storage

The integration of photo-thermal conversion and thermal energy storage is an efficient way to improve the solar energy utilization. Phase change material (PCM) with excellent thermal storage ability is often used in solar energy storage systems. However, PCMs suffer from liquid leakage, low thermal conductivity and insensitivity to light. This work used sol-gel and high-temperature calcination to modify the carbonized-wood (CW) by alumina nanoparticles loaded in the pores to improve the above issues. The combined microscopic and macroscopic test results showed that the modified carbonized-wood provided a good support structure for the paraffin wax (PW) to prepared carbonized-wood based composite phase change materials (CCPCMs). The CCPCMs exhibit noticeable hydrophobicity as well. The thermophysical properties of the CCPCMs were tested and the results showed that the CCPCMs possessed excellent encapsulation rate (85.98 %–91.65 %), enthalpy of phase transition (166.3–176.6 J/g), and good thermal reliability. By high-temperature carbonization and loading of alumina nanoparticles, the photo-thermal conversion efficiency of CCPCMs was optimized to 95.13 % and the surface overheating was weakened. In the simulation experiment of glass chamber, CCPCMs can store heat while maintaining the uniformity of the chamber's temperature. In conclusion, the novel CCPCMs developed in this work are highly promising in the field of solar thermal utilization and storage.

Optimizing thermal stability in permafrost regions: A comprehensive evaluation of encapsulated phase change material enhanced energy storage embankments

The melting of permafrost can cause serious damage to road structures. This study prepares a phase change geotextile (PCG) with heat absorption and waterproofing properties and proposes a new type of cooling structure called a phase change energy storage embankment (PCESE). A finite element model of the road is established to quantify the artificial permafrost table (APT), mean annual ground temperature (MAGT) at the bottom of the embankment, and mean daily cooling rate (MDCR) of the asphalt pavement surface under different PCESE structures. This study focuses on exploring the effects of the type of epoxy resin composite phase change material (ERPCM), dosage of ERPCM, and position of the PCG on various indices. The Entropy-TOPSIS method is used to evaluate the comprehensive performance of the PCESE and determine the optimal structure and optimization strategy. The results demonstrate that the addition of PCG to an embankment always improves the APT and MDCR, but does not necessarily reduce the MAGT. The optimal type of ERPCM, dosage of ERPCM, and position of PCG are ERPCM2, 12 kg/m2, and 3.0 m, respectively. The dosage of the ERPCM had the highest positive correlation with comprehensive performance. Considering the distribution of comprehensive performance and coefficient of variation under different structures, the recommended type of ERPCM, dosage of ERPCM, and position of the PCG are ERPCM1, 12 kg/m2, and 2.5 m, respectively.

Thermal performance of phase change material based heat exchanger filled with inorganic salt/expanded graphite

Solid-liquid latent heat storage, featured by the high-density energy storage capacity, is promising in facilitating the high-penetration renewable energy. However, the design of the heat exchanger is challenging due to the conflicting objectives between the heat transfer efficiency and energy storage capacity. To this end, this paper introduces a comprehensive evaluation index, based on which an orthogonal based design optimization method is proposed for heat exchangers filled with inorganic salt/expanded graphite composite phase change material (CPCM). A thermophysical properties based numerical model is built to describe and analyze the solidification and melting of CPCM. The comprehensive evaluation index is utilized to quantify the overall change in heat storage/release performance relative to the mass change of the baseline phase change heat exchanger. The orthogonal experimental method is employed to investigate the impact of various heat exchanger structural factors on the comprehensive performance, followed by optimization design. Simulation results indicated that the longitudinally finned heat exchanger outperforms the other two heat exchangers in terms of the comprehensive evaluation index. Moreover, the inlet fluid temperature exerts a more significant impact on the comprehensive evaluation index compared to the inlet fluid velocity. Additionally, the effects of pipe spacing, fin number, fin height, and tube material on the thermal performance of the longitudinally finned heat exchanger were examined and analyzed. Among these factors, the fin height was identified as the most substantial contribution to the heat transfer performance, while the tube material has a minor effect.

Conceptual design and numerical analysis of a miscibility gap alloy-based solid-state thermal battery for electric vehicles

Heating the passenger cabin of electric vehicles at low temperatures consumes a large amount of battery power, resulting in a significant reduction in cruising range. On-board thermal energy storage is an effective way to improve the cruising range of electric vehicles in winter. Miscibility gap alloy is a new type of shape-stabilized composite phase change material, which has the advantages of high energy storage density, high thermal conductivity, low cost, and good safety. Therefore, using it to heat electric vehicles can increase their cruising range, prolong battery life, and reduce cost. In this paper, the concept of a compact on-board solid-state thermal battery based on miscibility gap alloy is proposed for the first time, and the heat charging, thermal insulation and heat discharging performance of the design are analysed based on numerical simulations. The results show that the thermal battery can reach a heat storage density of 553.8 Wh/L, and the average heat discharging power can reach 1.326 kW. The results of this paper can provide guidance for the engineering development of miscibility gap alloy-based solid-state thermal batteries.