Phase Change Temperature Research Articles

NH4Al(SO4)2·12H2O-Na2SO4 eutectic-based phase change materials with excellent light absorbance, enhanced thermal conductivity, and high latent heat performance

A novel eutectic phase change material with light absorption and high thermal conductivity was successfully prepared. The based phase change material was ammonium aluminum sulfate dodecahydrate‑sodium sulfate eutectic phase change materials. The black Ti2O3 after ball milling was selected as light thermal conversion material which can absorb sunlight effectively and simultaneously convert the light to thermal and the expanded graphite was added to further improve the thermal conductivity of phase change materials. The phase change temperature of the eutectic phase change material was effectively regulated to 80 °C compared with 93 °C of pure aluminum sulfate dodecahydrate. The thermal conductivity of eutectic phase change materials with expanded graphite was enhanced to 1.16 W·m−1·K−1 compared with 0.53 W·m−1·K−1 of the pure eutectic phase change material. By adding Ti2O3, the combination material shows the best solar absorbance capacity of 87.96 % compared with the pure eutectic phase change materials of 73.43 %. The latent heat of the novel material was 190.97 kJ/kg. Considering their huge superiority of highly efficient use of solar energy in natural resources, the new novel ammonium aluminum sulfate dodecahydrate‑sodium sulfate eutectic-based phase change material with excellent light absorbance, enhanced thermal conductivity, and high latent heat performance is a very promising material for solar-thermal conversion and energy storage.

The study on the coupled influence of water saturation on heat and mass transfer processes within porous media under CW laser irradiation

Continuous wave (CW) laser irradiation induces temperature changes in various phases within porous media, accompanied by phase change and gas transport. Water saturation is a crucial factor influencing this context's moisture and heat transfer process. This paper addresses this issue by establishing a theoretical model for CW laser irradiation on unsaturated porous media. Through experiments and simulations, it studies the effects of different water saturations on heat and mass transfer under laser irradiation. The results indicate that the critical depth reflects the influence of water saturation under laser irradiation on the distribution of solid-phase temperature in both time and space dimensions. Specifically, an increase in water saturation enhances the uniformity of solid-phase temperature distribution, while the gas temperature exhibits a similar distribution pattern. For mass transfer processes, it increases the evaporation rate and Darcy velocity of porous media within the effective range of laser irradiation. Lower water saturation facilitates phase change processes and accelerates gas transport rates. Importantly, this trend remains consistent even with the emergence of dry-saturation zones. Additionally, the decrease in water saturation has a coupled promoting effect on gas temperature and mass transfer processes. Lowering water saturation can increase gas temperature and consequently enhance mass transfer processes. Simultaneously, enhancing mass transfer processes benefits heat exchange between the two phases. In the four sets of experiments, the conformity of the surface temperature rise curves obtained from experiments and simulations is good, indicating that the model can accurately reflect the temperature rise patterns of sand particles. In summary, this work provides valuable research results on the effects of different water saturations on laser irradiation-induced temperature rise, phase change, and gas and moisture transport within porous media. It lays a specific theoretical foundation for laser soil remediation technology.

Adjustable temperature and high thermal conductivity composite phase change material based on sodium acetate trihydrate–alanine/expanded graphite for thermal management of electronic devices

Phase change energy storage technology using phase change materials (PCMs) is a viable solution to effectively address the heat dissipation problems of electronic devices. Herein, we proposed to prepare a modified PCM using CH3COONa·3H2O (SAT) as main PCM, 9 wt% DL-Alanine (DL) as temperature modifier, and 2 wt% Na2HPO4·12H2O as nucleating agent. Calculations using density functional theory method confirmed that the adjustment of DL on phase change temperature of SAT was originated from the hydrogen bond between them. Then, the modified PCM was loaded into 14 wt% expanded graphite (EG) to obtain a composite PCM with a suitable phase change temperature of 52.9 °C, phase change enthalpy of 227.4 J/g as well as supercooling degree of 6.6 °C, and the thermal conductivity of the composite PCM was as high as 11.52 W·m−1·K−1. SEM and pore structure analyses showed that the modified PCM was successfully loaded into the pore structure of EG, and their combination was verified by XRD and FT-IR as a physical interaction. After 200 heating–cooling cycles, the phase change temperature and enthalpy of the composite PCM was basically unchanged along with consistent crystal structure and chemical composition, showing an excellent thermal reliability. A comparative analysis applied in a testing system showed that with loading of the composite PCM temperature control module, the critical time of the electronic chip was extended by 4670 s and the thermal equilibrium temperature was decreased by 20.4 °C, presenting a good thermal management performance. Therefore, the prepared composite PCM had great potential for application in thermal management of electronic devices.

Experimental study on supercooling performance optimization of sodium acetate trihydrate phase change energy storage materials

In response to the pressing demands for sustainable energy, the development of efficient energy storage materials and technologies has emerged as a focal point in contemporary research. Sodium acetate trihydrate (CH3COONa·3H2O, SAT), recognized for its potential as a mid-to-low temperature phase change material (PCM) in energy storage systems, encounters significant limitations due to its substantial supercooling effect and inferior thermal conductivity. Traditional approaches to enhance SAT's thermal performance often involve costly additives, which hinder their adoption on an industrial scale. This study introduces SAT as a base compound, and through a fusion blending method, binary eutectic hydrate salt composites (CPCMs) are synthesized with either sodium sulfate decahydrate (Na2SO4·10H2O, SSD) or disodium hydrogen phosphate dodecahydrate (Na2HPO4·12H2O, DHPD) in varying ratios. The results demonstrate that the prepared eutectic hydrates effectively reduce the supercooling degree of pure SAT from above 35 °C to below 10 °C, with the SAT/SSD-5/5 composition exhibiting the lowest supercooling at 3.17 °C. Notably, these eutectic blends possess appreciable latent heat capacities, with SAT/SSD-9/1 delivering 196.18 J/g, and exhibit improved thermal conductivity, as seen in SAT/SSD-3/7 with a coefficient of 0.8925 W/(m·K). Furthermore, the SAT-based eutectic hydrates are devoid of expensive additives, facile to manufacture, and applicable over a broad temperature range (20–60 °C), making them highly suitable for large-scale commercial applications.

Thermal conductivity enhancement of polyethylene glycol/NF composite as stabilized phase change materials for thermal energy storage

Polyethylene glycol (PEG) has the advantages of large latent heat of phase transition, a wide range of phase transition, and cheap price, but the application of PEG in the latent thermal energy storage (TES) systems is hindered due to its lower heat transfer rate and leakage. Porous metal foam has excellent thermal conductivity and high strength, which can effectively improve the problems of PEG. In this study, PEG/nickel foam (NF) composite phase change materials (PCM) were prepared by vacuum molten impregnation method using NF as substrate. It was found that PEG had good compatibility with NF, and the highest impregnation rate of PEG6000/NF reached 85.73 %. The thermal conductivity of PEG2000/NF can be increased to 1.58 1.58 W·m−1 K−1, nearly 4 times larger than that of pure PEG. The phase change temperature range of the composite PCM is 51–63 °C, and the phase change enthalpy is 67.8–126.3 J·g−1. Furthermore, the PEG/NF composite demonstrated outstanding photothermal conversion properties and high thermal stability, which can be widely used in the field of building temperature control and device heat dissipation.

Ag nanowires modified expanded graphite based composite phase change materials with enhanced thermal conductivity, light/electro-to-thermal performances

Phase change materials with excellent thermal energy storage property displayed great potential application in many fields, such as lithium battery thermal management, energy saving building and waste heat utilization. In this paper, a novel composite phase change material of Ag nanowires modified expanded graphite/lauric-myristic-palmitic acid (AgNWs@EG/LMP) with the function of photo/electro-thermal conversion property was prepared which the AgNWs@EG was acted as the matrix material and LMP was the phase change material. The composite exhibited high latent heat of 118.42 J/g at the phase change temperature of 33.62 °C with the LMP supporting ratio of 76.18%. The thermal conductivity of AgNWs@EG/LMP reached 4.23 W/(m∙K) which enhanced 1914% than that of LMP. The photo-thermal conversion efficiency reached 88.01% and the electro-thermal conversion efficiency was 65.4% with an input voltage of 1.5 V. Further results showed the composite AgNWs@EG/LMP possessed good chemical compatibility, good thermal stability and reliability. Therefore, the novel composite of AgNWs@EG/LMP with good thermal property and multi-energy conversion functions will process potential application in energy storage system and thermal management fields.

Phase change material properties identification for the design of efficient thermal management system for cylindrical Lithium-ion battery module

Performance and life of Lithium-ion battery packs in EVs and energy storage applications are limited by the thermal profile of cells during its life. Passive cooling technique based on Phase Change Material (PCM) is employed for mitigating thermal issues associated with Lithium-ion cells. The challenge with PCM materials is the trade-off between its latent heat of fusion, thermal conductivity and specific heat. Detailed CFD analysis is carried out to study the impact of PCM thermal properties on battery pack thermal profile and provide guidelines for PCM properties selection and usage of existing PCM materials. Impact of critical PCM properties such as latent heat (100–250 kJkg−1), thermal conductivity (0.2–23 Wm−1K−1), melting temperature and thickness of PCM material on thermal performance of a battery module during rapid discharge rate of 25 A (3.2C) is investigated. Battery module maximum temperature (Tmax) reaches 54°C and temperature difference (∆T) to 5.5°C while operating at 35°C with 124 kJkg−1and 0.2 Wm−1K−1. It is found that, PCM with higher latent heat (≥ 175 kJkg−1), thermal conductivity (≥ 3 Wm−1K−1), PCM thickness (≥ 3 mm) and appropriate phase change temperature 41-44°C exhibit improved heat dissipation for high discharge rates by effectively reducing the Tmax to 44.4°C and ∆T to 2.4°C (25 A and 35°C ambient). Further, ways to mitigate low latent heat capacity and thermal conductivity of PCM through increasing PCM material usage (i.e. inter cell distance) is emphasized. Results of the present study can be considered as a design tool for PCM development engineers which could be cost effective both in-terms of development time and effort.

Study on Thermophysical Properties and Phase Change Regulation Mechanism of Optically-Controlled Phase Change Materials: Synthesis, Crystal Structure and Molecular Dynamics.

Optically-controlled phase change materials, which are prepared by introducing molecular photoswitches into traditional phase change materials (PCMs), can convert and store solar energy into photochemical enthalpy and phase change enthalpy. However, the thermophysical properties of optically controlled PCMs, which are crucial in the practical, are rarely paid attention to. 4-(phenyldiazenyl)phenyl decanoate (Azo-A-10) is experimentally prepared as an optically-controlled PCMs, whose energy storage density is 210.0 kJ·kg-1, and the trans single crystal structure is obtained. The density, phase transition temperature, thermal conductivity, and other parameters in trans state are measured experimentally. Furthermore, a microscopic model of Azo-A-10 is established, and the thermophysical properties are analyzed based on molecular dynamics. The results show that the microstructure parameter (order parameters) and thermophysical properties (density, radial distribution function, self-diffusion coefficient, phase change temperature, and thermal conductivity) of partially or completely isomerized Azo-A-10, which are challenging to observe in experiments, can be predicted by molecular dynamics simulation. The optically-controlled phase change mechanism can be clarified according to the differences in microstructure. The optically-controlled switchability of thermophysical properties of an optically-controlled PCM is analyzed. This study provides ideas for the improvement, development, and application of optically-controlled PCMs in the future.

Green building material with superior thermal insulation and energy storage properties fabricated by Paraffin and foam cement composite

In the field of architecture and construction, foam cement has been gradually gaining popularity due to its outstanding attributes of reduced weight, carbon footprint, and potential thermal insulation effects. However, relying solely on the thermal insulation provided by the foam in foam cement lacks the capability to store and release heat. In this paper, a novel approach is proposed by directly incorporating paraffin into foam cement with non-continuous pores, creating a phase change foam cement. The addition of paraffin to foam cement, facilitated by the presence of surfactants in foam, allows the paraffin to disperse. In contrast, if paraffin is directly added to cement without the foam, it tends to aggregate. The internal pore structure, thermal performance, phase change temperature, and relaxation distributions were investigated through equipment such as scanning electron microscope (SEM), thermal conductivity meter, differential scanning calorimetry (DSC), and H1 nuclear magnetic resonance (NMR). Results indicate that paraffin/foam cement plays a dual function, effectively storing and releasing energy, significantly enhancing its thermal insulation performance. Particularly, the incorporation of 10 vol% paraffin content results in a notable 21.8 % reduction in the thermal conductivity, for foam cement with a density of 600 kg/m3. This is attributed to the heat storage capability of the phase-change paraffin, which absorbs heat as the surrounding temperature rises, synergistically collaborating with the foam. This presents a novel perspective for the development of green and energy-efficient building materials, contributing to the realization of sustainable energy utilization in the construction industry.

Thermal performance study of PCM embedded radiant cooling ceiling assisted by infrared-transparent silicon wafers

Phase change materials embedded radiant chilled ceiling (PCM-RCC) systems are great for cutting peak power demand and boosting energy efficiency, but they might not work as well in really humid areas due to condensation issues. Infrared-transparent silicon wafer-assisted PCM-RCC (ISW-assisted PCM-RCC) is proposed to improve the cooling capacity in this study. A heat transfer model of ISW-assisted PCM-RCC is established and its reliability is verified. Effects of thermal conductivity, phase change temperature, and control strategy on the thermal performance of ISW-assisted PCM-RCC are discussed by using the model. The simulation results show that the thermal conductivity of PCM is recommended to be above 0.6 W/(m·K), and the temperature difference between the lower limit of the selected PCM phase transition temperature range and the chilled water temperature should not be less than 1℃. The maximum cooling power of the system is more than 80 W/m2, 46 % higher than the non-condensing cooling capacity of traditional RCC at 70 % relative humidity conditions. Interestingly, the prolonged cold energy storage strategy at night should be avoided which is not friendly to the energy efficiency of the system. In short, the combination with ISW is an effective means to increase the cooling capacity of the PCM-RCC.

Enhancing thermal energy storage properties of blend phase change materials using beeswax.

This study aims to use beeswax, a readily available and cost-effective organic material, as a novel phase change material (PCM) within blends of low-density polyethylene (LDPE) and styrene-b-(ethylene-co-butylene)-b-styrene (SEBS). LDPE and SEBS act as support materials to prevent beeswax leakage. The physicochemical properties of new blended phase change materials (B-PCM) were determined using an X-ray diffractometer and an infrared spectrometer, confirming the absence of a chemical reaction within the materials. A scanning electron microscope was used for microstructural analysis, indicating that the interconnection of the structure allowed better thermal conductivity. Thermal gravimetric analysis revealed enhanced thermal stability for the B-PCM when combined with SEBS, especially within its operating temperature range. Analysis of phase change temperature and latent heat with differential scanning calorimetry showed no major difference in the melting point of the various PCM blends created. During the melting/solidification process, the B-PCMs possess excellent performance as characterized by W70/P30 (112.45J.g-1) > W70/P20/S10 (94.28J.g-1) > W70/P10/S20 (96.21J.g-1) of latent heat storage. Additionally, the blends tend to reduce supercooling compared to pure beeswax. During heating and cooling cycles, the B-PCM exhibited minimal leakage and degradation, especially in blends containing SEBS. In comparison to the rapid temperature drop observed during the cooling process of W70/P30, the temperature decline of W70/P30 was slower and longer, as demonstrated by infrared thermography. The addition of LDPE to the PCM reduced melting time, indicating an improvement in the thermal energy storage reaction time to the demand. According to the obtained findings, increasing the SEBS concentration in the composite increased the thermal stability of the resulting PCM blends significantly. Despite the challenges mentioned earlier, SEBS proved to be an effective encapsulating material for beeswax, whereas LDPE served well as a supporting material. Leak tests were performed to find the ideal mass ratio, and weight loss was analyzed after multiple cycles of cooling and heating at 70°C. The morphology, thermal characteristics, and chemical composition of the beeswax/LDPE/SEBS composite were all examined. Beeswax proves to be a highly effective phase change material for storing thermal energy within LDPE/SEBS blends.

Integrating interlayer ventilation into phase change walls: Comprehensive performance and optimization in summer

Integrating phase change materials (PCM) into building walls can improve the thermal performance of walls. However, phase change walls (PCW) in hot climates have poor thermal performance during nighttime due to the exothermic process of PCM. In this work, we proposed a novel PCW integrating with interlayer ventilation (IVPCW), which is innovative for all-day availability. Its comprehensive performance analyses and optimization were conducted. The results indicate that utilizing interlayer ventilation improved the comprehensive performance of the PCW. Moreover, the optimal phase change temperature range is [28 °C, 34 °C], the optimal phase change layer thickness is 30 mm, the optimal air delivery method is method 2, and the optimal air layer thickness is 50 mm. The average daily cooling load of IVPCW with the optimal parameter was 126.08 kJ/m2 during the cooling-season week, which was 43.7 % lower than the pre-optimization. Long-term performance analyses conclude that IVPCW can effectively reduce the cooling load, electrical cost, and CO2 emissions of air conditioning systems, which were 75.0 % lower compared with the ordinary wall (OW) and 59.1 % lower compared with PCW. In summary, IVPCW has a superior energy-saving and carbon-reducing performance to OW and PCW. This study established a theoretical foundation for the engineering implementation of IVPCW.

Superelastic Polymer Aerogel with Superamphiphilicity.

Elastic aerogels have become a research hot spot in both academia and industry recently. The reported elastic aerogels are all made of hard materials by controlling their shapes. Herein we report an elastic aerogel made of a polymer elastomer with entropy elasticity. In the aerogel, cross-linked carboxyl nitrile rubber nanoparticles with hydrophilicity are dispersed in hydrophobic derivative of styrene-maleic anhydride alternating copolymer, forming a very special micro-nano surface structure with hydrophilic protrusions and hydrophobic depressions on the aerogel wall; therefore, the aerogel is not only superelastic but also superamphiphilic. A leak-free phase-change composite was prepared using the aerogel and paraffin, which can maintain at phase change temperature of paraffin for a longer time than the traditional one. The aerogel is also extremely suitable for desalination evaporators in solar-driven interfacial evaporation technology due to its superamphiphilicity, superelasticity, and ability to absorb sunlight. Exceptional evaporation rate of 2.78 kg·m-2·h-1 and evaporation efficiency of 170% could be reached even without using expensive light-absorbing materials. The evaporation rate exceeds that of most evaporators with expensive light-absorbing materials, and the evaporation efficiency exceeds the theoretical limit of conventional 2D solar evaporators. Both the phase-change composite and the evaporator can be easily recovered because the novel superelastic aerogel reported in this work is also recyclable.

Experimental investigation on hydrated salt phase change material for lithium-ion battery thermal management and thermal runaway mitigation

To efficiently ensure the suitable temperature for lithium-ion batteries, battery thermal management system based on phase change material (PCM) have gained considerable attention. A shape-stabilized composite PCM was prepared using the mixture of Na2SO4·10H2O and KAl(SO4)2·12H2O hydrated salts as phase change substrate, expanded graphite as thermal conductive filler and open-cell polyurethane foam as support material. The composite PCM containing 4 wt.% expanded graphite displayed a satisfied phase change temperature of 30.8 °C and 69.8 °C, high latent heat of 226.9 J/g, and good thermal conductivity of 1.39 W/(m·K). Meanwhile, it obtained a low subcooling degree, good leakage resistance, and excellent flame retardancy properties. Under PCM cooling in sandwich structure, during 0.5C charging and 1.5C discharging cycles, the maximum temperature and maximum temperature difference of battery were 52.47 °C and 2.20 °C, decreased by 20.4 % and 59.7 % respectively compared with nature air cooling. Furthermore, the composite PCM could significantly relieve the thermal runaway propagation between lithium-ion batteries. This work provides a feasible design and application strategy of hydrated salt based PCMs for battery thermal management and thermal runaway mitigation.

Enhanced piezoelectrical properties of Pb(Zn1/3Nb2/3)O3 - PbTiO3 single crystals by AC poling

We investigated the effectiveness of AC poling (ACP) processes for [001] direction oriented Pb(Zn1/3Nb2/3)O3-0.055PbTiO3 (PZN-PT) single crystals (SCs) and obtained a dielectric constant ε 33 T/ε 0 of 6680 and piezoelectric strain constant d 33 of 2760 pC/N, a piezoelectric charge constant g 33 of 46.7 × 10−3 Vm/N, and a figure of merit (FOM) (d 33 × g 33) of 129 × 10−12 m2/N. These values were 19%, 31%, 10%, and 45% higher than those of DC poling PZN-PT SC, respectively. The phase change temperature T pc, Curie temperature T c, and acoustic impedance (Z 33) of the ACP PZN-PT SC were 121 °C, 165 °C, and 30.5 MRayls, respectively. Compared with Pb(Mg1/3Nb2/3)O3−0.3PbTiO3 SCs, the higher T pc, T c, and FOM and lower Z 33 of the PZN-PT SCs enable the applications in high temperature with superior Z 33 matching to water and human body than conventional Pb(Mg1/3Nb2/3)O3−0.3PbTiO3 SCs , and these findings are vital for a wide range of ultrasonic transducer applications.

Composite energy storage cement-based mortar including coal gasification slag/paraffin shape-stabilized phase change material: physical, mechanical, thermal properties

Using renewable sources to generate energy is an approach to realize a sustainable energy system. Utilizing gasification slag, a solid waste from the coal gasification process, as a porous material not only substantially increases the value of the waste but also enhances thermal performance. This study develops a novel shape-stabilized coal gasification slag/paraffin (CGS-P) phase-change material for use in cement mortar to reduce indoor temperature fluctuations. Using a simple impregnation method, paraffin is incorporated into porous coal gasification slag to produce CGS-P. Coal gasification slag containing 30 % paraffin (CGS-P(30 %)) can maintain its structure without leakage at 60 °C. The thermal and chemical characteristics as well as the specific surface area of CGS-P(30 %) are characterized via X-ray diffraction (XRD), Fourier-transform infrared (FT-IR) spectroscopy, Brunauer–Emmett–Teller (BET) analysis, differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and scanning electron microscopy (SEM)–energy-dispersive X-ray spectroscopy. The results of XRD and FT-IR analyses indicate that CGS-P(30 %) is a combination of paraffin and CGS, with no new substances formed. Furthermore, the BET, SEM, and TGA results confirm that the pores in CGS can effectively encapsulate approximately 30 % paraffin and that CGS-P(30 %) exhibits good thermal stability. The DSC analysis results show that CGS-P(30 %) has suitable phase-change temperatures and latent heat (18.02 °C and 59.30 J/g, respectively, during the endothermic phase). Furthermore, incorporating 30 % CGS-P(30 %) into the cement mortar (CESCM30) results in good mechanical and thermal performance. Particularly in hot climates, CESCM30 can notably reduce indoor temperatures, alleviate indoor cooling energy consumption, and indirectly reduce CO2 emissions. Therefore, CGS derived CGS-P is a promising material for accommodating solar thermal energy.

Performance Analysis of Finned-Tube Heat Exchanger Charged with Phase Change Material for Space Cooling

The performance of a latent heat storage unit comprised of phase change material (PCM) enclosed in a finned-tube heat exchanger was evaluated experimentally and theoretically to determine its viability to condition a space during summer. The internal and external design conditions of a typical building were selected and analyzed to determine the type of PCM, and the phase change temperature required for space cooling. Subsequently, a PCM of Plus-ice A17 was selected and charged into a small-scale finned-tube heat exchanger. Extensive measurements were conducted on the PCM heat exchanger at different operating conditions. Meanwhile, a three-dimensional computational fluid dynamics model for the PCM heat exchanger was developed and validated with the experimental measurements and thus simulated. When the airflow velocity increases from 1.3 m/s to 6 m/s, the phase change periods decrease by 25% and 13% for the PCM charging and discharging processes respectively. When the PCM thermal conductivity increases from 1 W/(m·K) to 8 W/(m·K), the phase change periods reduce by 36.3% and 47.7% for the PCM charging and discharging processes respectively. In addition, for the same increased range of PCM thermal conductivity, the charging energy efficiency increases by 16.3%, and the discharging energy ratio drops by 7.1%.

Experimental investigation on battery thermal management using phase change materials with different arrangement schemes

Thermal management is imperative for regulating battery temperature during operation. In this paper, lithium iron phosphate batteries were taken to experimentally investigate the battery thermal management system module utilizing phase change materials. Various phase change material (PCM) plates with uniform and gradient phase change material arrangements were produced by pressing phase change material powder to closely adhere to the battery. The experimental results illustrated that the phase change material plate had a good temperature uniformity effect on the battery, and this effect became more noticeable under high-rate battery discharge. Over 80% of the experimental group’s the maximum temperature difference could be maintained within 3 °C. In addition, there was an optimal range for phase change material plate thickness, the effect of reducing the battery maximum temperature weakened and the efficiency of phase change material utilization decreased when the phase change material plate thickness exceeded a critical value. Specially, a gradient arrangement of the phase change material with different phase change temperatures had better cooling effect on the battery. Compared with uniform arrangement of PCM, the temperature difference with gradient arrangement of PCM was decreased by 55.6%, 70.8%, and 77.4% at 2C, 2.5C, and 3C discharge rates, respectively. To guarantee that the battery’s high heat-generating areas can always be cooled by phase change material through latent heat absorption in the middle and later stages of discharge, phase change material with higher phase-change temperatures should be placed in these areas, which can coordinate the non-uniform heat generation of battery and prevent severe temperature rise as well as further reduce the maximum temperature difference. The findings presented in this study provide new insights for designing a battery thermal management system utilizing phase change material.

Double emulsion templates for efficient production of phase change microcapsules

The utilization of phase change materials (PCMs) in thermal storage technology exhibits great potential for various applications in thermal management and latent heat storage systems. However, leakage of organic PCMs hinders its practical application. Encapsulation of PCMs in microcapsules with polymer shells can prevent PCM leakage while improving heat transfer and stability. In this study, shell monomers were introduced as an immiscible third phase into the traditional o/w two-phase emulsion system, and the formed three-phase complex emulsion was dynamically reconfigured to exhibit a core–shell encapsulated conformation induced by interfacial tension, resulting in the formation of a thermodynamically stable double emulsion. Microcapsules with 1,6-hexanediol diacrylate (HDDA) shells were successfully prepared using this double emulsion as a template. The emulsion configuration is of significant advantage in promoting stable encapsulation of the phase change material in the shell material, resulting in fast and efficient encapsulation and improved utilization of the phase change material. Phase change microcapsules with different phase change temperatures were prepared and characterized using n-octadecane (C18), methyl stearate (Mes), n-eicosane (C20) and n-docosane (C22) as phase change materials, respectively. Results show that the prepared microcapsules are spherically integrated, with smooth surfaces and obvious core–shell structures, and the enthalpies of phase transition of C18, Mes, C20 and C22 microcapsules are as high as 171.86, 122.37, 165.77 and 178.69 J/g, respectively. These microcapsules exhibit excellent thermal stability and durability and the encapsulation efficiencies exceed 99.7 % at different phase change temperatures. Furthermore, the potential applications of PCM microcapsules in the field of temperature regulation were also demonstrated. This double-emulsion template method provides a straightforward, rapid and scalable approach for the mass production of microcapsules with different core–shell compositions.

Asymptotic Behavior and Numerical Simulations of a Conservative Phase-Field Model with Two Temperatures

One of the types of problem that has attracted the attention of mathematicians in recent years is the phase field system. The field of application includes materials science, where phenomena such as phase separation in alloys, crystal formation and thermal welding are legion. Among these phase transition systems, the family of conservative systems is very popular with industry. Indeed, minimising losses in production systems is a major issue for their profitability. In this paper, we study the well-posedness of the formulation and the asymptotic behaviour of the solutions, by proving the existence of a finite-dimensional global attractor for a conservative variant of the two-temperature phase field system with homogeneous Neumann boundary conditions. The inclusion of two temperatures in the definition of the enthalpy of the system is a necessity in the case of a non-simple material. In a simple material, once the phase-change temperature has been reached, the temperature of the system remains constant until the material has completely changed state. This is not true in the case of a non-simple material, where an increase in the temperature of the system is observed even after the phase-change temperature has been reached. To conclude the work, we present a method for numerically approximating the solution and carry out some numerical tests.