Latent Heat Of Phase Change Material Research Articles

Thermal management optimization strategy for lithium-ion battery based on phase change material and fractal fin

In order to solve the problem of temperature control of lithium-ion battery (LB) in electric vehicles, a new battery thermal management system (BTMS) based on phase change material (PCM) coupled fractal fin (FF) was proposed. The effects of latent heat, thickness, and thermal conductivity of PCM (paraffin) on the thermal properties of BTMS were investigated. Subsequently, the fin structure was added to the BTMS to improve the heat transfer capacity, and the number of fins, aspect ratio, material and structure morphology were explored. The results show that when the latent heat of PCM is 200 kJ/kg, the thickness is 2 cm, and the thermal conductivity is 0.8 W/(m·K), the temperature of LB is 34.9 K lower than that of LB without the BTMS at 4C. In addition, the BTMS has the best performance when FF-II with a fin count of 5, aspect ratio of 7:1, and material of carbon steel are used. The temperatures of LB are 301.8 K, 303.9 K, 305.4 K, and 307.3 K at 1 to 4C, respectively, and the temperature difference in BTMS can be controlled within 2.5 K. This study provides some guidance for the optimization of BTMS.

Evaluating passive PCM performance in building envelopes for semi-arid climate: Experimental and numerical insights on hysteresis, sub-cooling, and energy savings

This study evaluates the performance of macro-encapsulated Phase Change Materials (PCMs) integrated into building envelopes for semi-arid climates, focusing on typical Moroccan construction using hollow concrete blocks. The primary objective is to assess the discrepancies between experimental and numerical analyses, particularly in hysteresis, sub-cooling, and energy savings. Given the widespread reliance on numerical tools like EnergyPlus for PCM simulations, the accuracy of manufacturer-provided latent heat values is investigated. The methodology involves constructing two identical test buildings, one equipped with PCM panels and another as a reference. Experimental data were collected in June 2023, assessing temperature fluctuations and energy savings. Differential Scanning Calorimetry (DSC) tests at varying scanning rates were conducted to analyze PCM behavior, including hysteresis and sub-cooling effects. Numerical simulations were then performed to compare energy performance. Besides, the results reveal that sub-cooling significantly limits PCM efficiency, with only 43 % of the PCM's latent heat capacity utilized. At the same time, hysteresis was found to be negligible in the field test. Cooling energy consumption was reduced by 20 %, with a corresponding 2.3 °C reduction in temperature fluctuations. However, the PCM's latent heat potential is underutilized due to sub-cooling. This research underscores the need for conducting DSC measurements at specific scanning rates to reflect regional climate conditions and suggests that simulation models should adjust latent heat utilization of the PCM. The study advocates for the use of composite PCMs, which could mitigate sub-cooling and enhance overall performance. These findings contribute to improving PCM integration in passive building designs, offering practical recommendations for better energy efficiency in semi-arid climates.

Numerical study on heat restoration cycle performance of energy pile with backfilling PCM

The numerical analysis of energy pile backfilled with phase change material (PCM) was performed for the renewable geothermal energy utilization in building energy savings. Different operation modes and the melting temperature, latent heat, thermal conductivity of the PCMs within the energy piles were discussed to obtain the optimal parameters. Further, the restoration and heat transfer performance of energy piles were also analyzed for the prolonged operation. It was concluded that relatively higher latent heat and thermal conductivity were preferable to enhance the heat transfer rate per meter (Qm) of the PCM-backfilled energy pile. However, a relatively lower PCM latent heat may help to full utilization and restoration of PCMs during every cycle of cooling and heating when energy pile works. An ideal melting temperature of PCM is probably close to the initial soil temperature to achieve preferred restoration and heat transfer performance, rather than the inlet fluid temperature. In heating 12 h and cooling 12 h alternate mode, taking continuous operation as a reference, the Qm and the restoration rate of pile wall temperature of the PCM-backfilled energy pile were increased by 32.7 % and 52.5 % after operating 720 h.

Numerical study and experimental validation of a porous biochar supported form stable composite for thermal energy storage

This study numerically investigates the performance of the melting process for a biochar-based phase change material latent heat energy storage system. The melting processes of a composite made from softwood biochar combined with paraffin RT28, were compared numerically using the equilibrium porous medium model in ANSYS Fluent. The set up was validated through results from previous literature and experimental work. The enhancement in melting was compared to the pure PCM melting scenario and the effects of different paraffins, boundary conditions and inclination angle were investigated for real world application. Softwood biochar composites significantly surpass the performance of paraffin alone, reducing the melting time by 79 %. Different paraffins within the softwood composite produced different melting times, ranging from 2565 s to 4790 s. In terms of inclination angle adjusting to 90° produced steadier heating and reduced the melting time by 63 % in the composite. These findings offer insights into optimising latent heat thermal energy storage systems for improved performance and reduced energy wastage, highlighting the potential of biochar composites in sustainable energy solutions.

Investigation of double-PCM based PV composite wall for power-generation and building insulation: Thermal characteristics and energy consumption prediction

The integration of phase change material (PCM) with building-integrated photovoltaic (BIPV) presents a compelling approach to enhance solar energy utilization and mitigate indoor thermal loads, contributing to energy-efficient and low-carbon building development. Traditional BIPV-PCM structures, however, struggle to balance PV efficiency and thermal insulation, particularly with varying PCM wall positions. To address this situation, this study introduces a novel double-PCM BIPV composite envelope (BIPV-dPCM). An experimentally validated dynamic heat transfer model was developed and used to perform a comparative simulation analysis with three reference systems to quantify the energy-saving potential of the BIPV-dPCM, focusing on PV output and wall insulation effectiveness metrics. Further dimensionless parametric analysis were carried out to investigate the systematic performance of the two PCMs at different relativities. In addition, the coupled working mechanism of the BIPV-dPCM system concerning the power generation performance and thermal insulation performance under transient variations is explored. It was found that the BIPV-dPCM showcases superior thermoelectric coupling performance compared to three alternative enclosures. Incorporating two PCMs significantly enhances electrical exergy efficiency by 11.66 % and thermal exergy efficiency by 1.54 %, surpassing other reference systems. The increase in PCM latent heat ratio has a limited effect on performance gain. Notably, as the PCM thickness ratio exceeds 1, the decline in P value decelerates, for every 0.5 increment in the g, the P value diminishes by merely 0.2 %. The ideal h is identified between 1 and 1.5, with 1.5 being optimal for energy conservation objectives. Additionally, the self-sufficiency coefficient (SSC) of the BIPV-dPCM remains robust, sustaining a range of 55 % to 65 % over prolonged periods. This study offers novel perspectives and serves as a design reference for optimizing building energy systems and enhancing cooling efficiencies in subtropical climates.

Experimental study of a novel Radiative cooling-Dual phase change material roof under hot summer and warm winter climate

In hot summer and warm winter climates, phase change materials (PCMs), with their ability to absorb and store thermal energy, can effectively reduce indoor temperature fluctuations and lower cooling loads when applied to roofs. Therefore, this study proposes a novel Radiative cooling-Dual phase change material (RC-DPCM) roof and conducts experimental research on its regulation of indoor and outdoor thermal environments. This energy-efficient roof integrates radiative sky cooling with PCM latent heat storage technologies within a compact building envelope. The innovative dual-PCM configuration can store heat from both indoor sources and outdoor solar radiation during the day through integrated PCM layers. At night, radiative cooling materials emit heat to the deep universe, helping the PCM layers complete solidification. The thermal performance of the RC-DPCM roof was tested in hot summer and warm winter climates compared to other roof designs: a single layer of aluminum (AL) roof, the Aluminum-Thermal insulation (AL-TH) roof, the Radiative cooling (RC) roof, the Radiative cooling-Outside phase change materials (RC-OPCM) roof, and the Radiative cooling-Inside phase change materials (RC-IPCM) roof. Results showed that the RC-DPCM roof significantly improved indoor thermal comfort and efficiency. Compared with the AL roof, the RC-DPCM roof reduced the average indoor temperature by 1.13 °C (or 2.49 °C during working hours) and continuously dissipated heat from the indoor environment to the ambient environment, reducing the cooling load. Additionally, the RC-DPCM roof achieved a 172.9 % average cooling load reduction during working hours, outperforming other roofs, thus demonstrating its potential as an innovative solution for sustainable and energy-efficient buildings. The RC-DPCM roof effectively reduced peak indoor temperatures and cooling load, demonstrating its potential as an innovative solution for sustainable and energy-efficient buildings.

A study on a battery pack in a hybrid battery thermal management system integrating with thermoelectric cooling

An inherent limitation of lithium-ion batteries is their restricted use within a specific thermal working range. To address this problem, efficient battery thermal management systems (BTMS) are required to dissipate the heat created by the cells in the battery pack. In order to control the maximum temperature and minimise the temperature difference through the battery pack during a 5C discharging process, this study investigates a phase change material (PCM)-porous battery thermal management system, cooled by thermoelectric coolers (TEC) on its walls. To calculate the heat generation of Li-ion batteries, the equivalent circuit model (ECM) is employed. In this model, a battery is made up of a set of electric elements, including R–C pairs. Different PCM and porous materials are studied to determine the most suitable material for controlling the thermal behaviour of the battery pack. The study reveals that the solidus temperature and latent heat of PCM are the two most crucial factors in PCM selection. A thermoelectric cooler is an instrument that uses electrical energy to transfer heat from one side of the device to the other, depending on the current direction. The study examines the use of a TEC (thermoelectric cooler) under various ambient temperatures and applied voltage differences. The results demonstrate that adjusting the voltage difference between the two TEC heads from 900 to 1500 mV, while the ambient temperature ranges from 303 K to 323 K, allows for achieving a cold plate temperature between 288 K and 308 K. The designed BTMS is tested in various TEC positions, and it is shown that when TECs are used on side walls, the maximum temperature of the battery back can decrease up to 1 K, and better temperature uniformity is observed.

Thermal modeling of porous medium integrated in PCM and its application in passive thermal management of electric vehicle battery pack

The integration of a composite of porous medium with phase change material (PCM) offers significant advantages in thermal management systems, enhancing heat transfer efficiency and addressing various thermal regulation challenges. This approach utilizes the PCM's latent heat absorption and the enhanced thermal conductivity provided by the porous medium, resulting in optimized system performance. Its applicability spans across electronics cooling and building insulation systems. However, predicting the thermal behavior of this composite material is challenging, necessitating computational tools to anticipate its response under different conditions and evaluate its influence on cooling strategies. The objective of this study is to create a computational tool specifically tailored to evaluate constitutive parameters of this composite material, thereby providing a comprehensive description of its thermal behavior. To achieve this goal, the multiscale homogenization principle is employed to assess the composite's effective thermophysical material properties using the representative volume element approach. The repeating unit cell of the aluminum lattice is incorporated into the PCM to define a representative volume element. The finite element method (FEM) is utilized to solve the three-dimensional homogenization problem, yielding an orthotropic effective thermal conductivity due to the inherent symmetry of the repeating material cell. Moreover, the study leverages the apparent heat capacity method to effectively manage the phase transitions within the PCM domain, utilizing smooth and temperature-dependent functions to accurately describe the thermophysical properties of the PCM. Integrating the composite into battery pack thermal management, this study thoroughly examines thermal dynamics by comparing outcomes with and without PCM integration. The transient thermal problem is accurately tackled using the FEM, employing the evaluated effective constitutive parameters of the homogenized composite to minimize computational effort. The results indicate a notable decline in the highest temperatures of the battery pack, leading to a reduction of about 14 °C at the specific moment when the phase change material fully transitions into its liquid form. The obtained results emphasize the effectiveness and practical feasibility of the proposed thermal management strategy. The modeling approach presented provides a robust tool with significant efficiency in reducing computational time for analyzing the thermal behavior of large models, as the utilization of the homogenization technique notably decreases the computational time.

Mechanical Properties and Durability of Composite Cement Pastes Containing Phase-Change Materials and Nanosilica.

Escalating global surface temperatures are highlighting the urgent need for energy-saving solutions. Phase-change materials (PCMs) have emerged as a promising avenue for enhancing thermal comfort in the construction sector. This study assessed the impact of incorporating PCMs ranging from 1% to 10% by mass into composite Portland cement partially replaced by fly ash (FA) and nanosilica particles (NS). Mechanical and electrochemical techniques were utilized to evaluate composite cements. The results indicate that the presence of PCMs delayed cement hydration, acting as a filler without chemically interacting within the composite. The combination of FA and PCMs reduced compressive strength at early ages, while thermal conductivity decreased after 90 days due to the melting point and the latent heat of PCMs. Samples with FA and NS showed a significant reduction in the CO2 penetration, attributed to their pozzolanic and microfiller effects, as well as reduced water absorption due to the non-absorptive nature of PCMs. Nitrogen physisorption confirmed structural changes in the cement matrix. Additionally, electrical resistivity and thermal behavior assessments revealed that PCM-containing samples could reduce temperatures by an average of 4 °C. This suggested that PCMs could be a viable alternative for materials with thermal insulation capacity, thereby contributing to energy efficiency in the construction sector.

Realizing rapid cooling and latent heat recovery in the thermoelectric-based battery thermal management system at high temperatures

To realize rapid cooling of the battery at high temperatures and effective latent heat recovery from phase change materials (PCMs), a thermoelectric-based battery thermal management system (BTMS) is proposed. Additionally, a transient multiphysics numerical model is developed to predict the system's thermal performance, and the concept of the latent heat recovery rate of PCMs is introduced. Results show that the introduction of thermoelectric coolers (TECs) significantly enhances the system's efficiency in cooling the battery at high temperatures (Stage 1) and recovering PCM latent heat (Stage 2). The overall thermal performance can be further improved by utilizing PCMs with a higher mass fraction of expanded graphite (EG) or increasing the TEC input current. Moreover, after the end of Stage 2, the power supply for TECs is interrupted, and the system enters Stage 3, which only relies on PCMs to control the battery temperature. The duration of Stage 3 increases with the EG mass fraction, achieving a peak of 3830 s at an EG mass fraction of 12%. Considering the thermal performance and power consumption of the system, the optimal solution is determined as an EG mass fraction of 12% and a TEC input current of 4 A. In this situation, the required time for Stage 1 and Stage 2 is 170 s and 620 s, with the latent heat recovery rate of PCMs up to 361.94 J/kg/s. The findings will provide new insights for the development of the thermoelectric-based BTMS.

Structure Design and Heat Transfer Performance Analysis of a Novel Composite Phase Change Active Cooling Channel Wall for Hypersonic Aircraft.

Efficient and stable heat dissipation structure is crucial for improving the convective heat transfer performance of thermal protection systems (TPSs) for hypersonic aircraft. However, the heat dissipation wall of the current TPS is limited by a single material and structure, inefficiently dissipating the large amount of accumulated heat generated during the high-speed maneuvering flight of hypersonic aircraft. Here, a convection cooling channel structure of TPS is proposed, which is an innovative multi-level structure inspired by the natural honeycomb. An active cooling channel (PCM-HC) is designed by using a variable-density topology optimization method and filled with phase change material (PCM). Numerical simulations are used to investigate the thermal performance of the PCM-HC wall, focusing on the influence of PCM properties, structural geometric parameters, and PCM types on heat transfer characteristics. The results demonstrate that the honeycomb-like convection cooling channel wall, combined with PCM latent heat of phase change, exhibits superior heat dissipation capability. With a heat flux input of 50 kW/m2, the maximum temperature on the inner wall of PCM-HC is reduced by 12 K to 20 K. Different PCMs have opposing effects on heat transfer performance due to their distinct thermophysical properties. This work can provide a theoretical basis for the design of high-efficiency cooling channel, improving the heat dissipation performance in the TPS of hypersonic aircraft.

Influence of PCMs on thermal performance of wet fire protective clothing

The inclusion of phase change materials (PCMs) in firefighting protective clothing (FPC) has been previously shown to be beneficial during the exposure stage, but detrimental in the post-exposure, mainly due to PCM latent heat release towards the skin, after the exposure. It is unclear whether that is also the case for when the FPC is wet. Hence, in this study, a one-dimensional numerical approach is used to study the effect of PCM parameters (PCM mass, melting temperature) and global heat flux, on the thermal performance of a wet fire protective clothing. It is concluded that under wet conditions, the PCM amount, and its phase change temperature have a significant effect on thermal performance, depending on the heat exposure scenario considered. Great benefits are observed in introducing PCMs to prevent water condensation near the skin, but at the cost of greater PCM re-solidification skin damage.

Analysis of Thermal Management Strategies for 21700 Lithium-Ion Batteries Incorporating Phase Change Materials and Porous Copper Foam with Different Battery Orientations

The significant amount of heat generated during the discharge process of a lithium-ion battery can lead to battery overheat, potential damage, and even fire hazards. The optimal operating temperature of a battery ranges from 25 °C to 45 °C. Hence, battery thermal management cooling techniques are crucial for controlling battery temperature. In this work, the cooling of 21700 lithium-ion batteries during their discharging processes using phase-change materials (PCMs) and porous pure copper foams were simulated. The effects of discharge intensities, battery orientations, and battery arrangements were investigated by observing the changes in temperature distributions. Based on current simulations for a 2C discharge, air-cooled vertical batteries arranged in unidirectional configuration exhibit an increase in heat dissipation by 44% in comparison to the horizontal batteries. This leads to a decrease in the maximum battery temperature by about 10 °C. The use of either PCMs or copper foams can effectively cool the batteries. Regardless of the battery orientation, the maximum battery temperature during a 2C discharge drops dramatically from approximately 90 °C when air-cooled to roughly 40 °C when the air is replaced by PCM cooling or when inserted with a copper foam of 0.9 porosity. If the PCM/copper foam approach is implemented, this maximum temperature further decreases to slightly above 30 °C. Although not very significant, it has been discovered that crossover arrangement slightly reduces the maximum temperature by no more than 1 °C. When a pure copper foam with a porosity ranging from 0.90 to 0.97 is saturated with a PCM, the excellent thermal conductivity of pure copper, combined with the PCM latent heat absorption, can best help maintain the battery pack within its range of optimal operating temperatures. If the porosity of the copper foam decreases from 0.95 to 0.5, the volumetric average temperature of the batteries may increase from 30 °C to 31 °C.

Performance investigation and optimization of latent heat exchanger with pin fins based on non-uniform deployment strategy

Latent heat storage technology is an essential way of efficiently utilizing industrial residual heat, which helps to the objective of carbon neutrality in all countries. In this work, latent heat exchangers with pin fins are numerically investigated based on non-uniform deployment strategy and then optimized according to response surface method. The influences of rotation angle, non-uniform fin pitch, non-uniform fin length and combination of phase change materials with different melting temperatures on thermal storage performance are studied. Results show that the increment of rotation angle facilitates the reduction of complete melting time, and the optimal angle accelerates the melting speed by 10.3% compared to the 0° angle. The arrangements of gradually decreasing fin pitch and gradually increasing fin length along flow direction of heat transfer fluid improve the heat storage performance, which can reduce the complete melting time by 7.3% and 22.2% respectively, compared to the uniform arrangement. The multiple phase change materials latent heat exchanger with high melting temperature phase change material placed in high temperature region and low melting temperature phase change material in low temperature region can make better utilization of heat from heat transfer fluid, which can improve the melting speed by 16.8% compared with the single phase change material latent heat exchanger. The optimized latent heat exchanger based on response surface method reduces the complete melting time by 23.4% compared to the original model. In conclusion, the heat storage performance of latent heat exchanger with pin fins effectively improved by adopting the non-uniform deployment strategy.

Experimental study of a latent heat thermal energy storage system using erythritol for medium temperature applications

Using solar energy and waste heat for medium-temperature thermal applications depends on efficient and economical heat storage development. Developing a compact thermal energy storage system is essential to use excess thermal energy from a source in a process or to shift the utilisation time of solar thermal energy or recovered waste heat. Phase change materials are commonly used for energy storage applications globally. In this work, a latent heat thermal energy storage (LHTES) system with 2.37 kg of Erythritol as the phase change material (PCM) has been studied. A shell and tube heat storage system is selected due to its effectiveness in heat transfer. Synthetic silicone oil Hi-Tech Therm-60 was used as heat transfer fluid. Thermal stability tests in a differential scanning calorimeter (DSC) for a small sample mass and a specifically designed experiment for a larger sample mass were performed to assess the stability of the PCM. The time-dependent temperature distribution inside the storage system and the effect of heat transfer fluid (HTF) inlet temperature on the charging behaviour were studied during the charging process. Charging time and melt fraction have been calculated. No significant change in melting temperature and a 10% reduction in latent heat of PCM was observed in the thermal stability test for a small sample mass in DSC. The charging time of the storage device was observed to be 91–97 min and 195 min for 140 °C and 130 °C HTF inlet temperatures, respectively. The total stored energy in the system was 922 kJ with a Stefan number of 0.59. Temperature variation during the charging process inside the storage also suggests a buoyancy effect, leading to increased natural convection during the melting process.

Numerical investigation of heat transfer mechanism in an embedded PCM-TEG for better overall performance under the fluctuating heat source

Using phase change materials (PCM) can effectively ensure the stable operation of semiconductor thermoelectric generators (TEGs). Conventional PCM-TEG structures exhibit relatively poor output performance due to energy barriers caused by low thermal conductivity. The embedded PCM-TEGs proposed in this study can address this issue well by adopting variable structure composite forms of PCM and TEG, resulting in a more complex heat transfer mode than traditional systems. To evaluate embedded systems' characteristics and performance enhancement methods, this paper first establishes a multiphysics mathematical model for embedded PCM-TEGs. Then, employing the TOPSIS method, an optimal embedded structure that considers system output and stability is obtained. Finally, we investigate the effects of key parameters on system performance, including PCM volume, latent heat, melting point, and metal-added composite materials. The CCC PCM-TEG (embedded PCM-TEG with PCM closer to the cold side) exhibits superior performance with a 28.6 % increase compared to conventional structures. For a given PCM volume, embedded structures with equal heights show better performance due to weak influence from asymmetric configurations on internal heat flow direction. Unlike traditional PCM-TEGs, metal-added composite PCMs in embedded structures reduce the temperature difference range across TEGs and thus deteriorate system performance.

Thermal behavior of phase change plates using tunnel lining GHEs for cool storage: Effect of pipe design parameters and PCM latent heat

An innovative energy storage technique of phase change plates (PCPs) using tunnel lining ground heat exchangers (GHEs) for cool storage facilitates the geothermal energy extraction and usage, which can serve tunnels and buildings cooling. In this study, numerical simulation was employed to analyze and assess this new energy storage technique. A coupled computational model of PCPs and tunnel lining GHEs was established to explore and analyze the thermal behavior of PCPs under varying PCP pipe design parameters and phase change material (PCM) latent heat values. The results show that at the same PCP pipe length, the effect of PCP pipe configuration on the drop rate of the PCM liquid fraction and the ratio of solid PCM is relatively evident after the cold energy charging operation mode of PCPs for a certain time. The energy storage time of the PCP under Shape 5 PCP pipe configuration reduces by 11.1 %, 26.7 %, 7.1 %, and 28.8 % compared to Shape 1, Shape 2, Shape 3, and Shape 4 PCP pipe configurations. Increasing the PCP pipe length can remarkably accelerate the drop rate of PCM liquid fraction and increase the ratio of solid PCM inside the PCPs. The energy storage time of the PCP saves by 75.0 % and 40.9 % as the PCP pipe length increases from 0.9 and 1.7 m to 2.5 m. Specifically, the energy storage time of PCPs decreases exponentially with an increase in the PCP pipe length. Moreover, PCM latent heat is a key material property to affect the PCM liquid fraction variation and the ratio of solid PCM inside the PCPs. The energy storage time of the PCP reduces by 70.7 % and 53.0 % when the PCM latent heat decreases by 200 and 100 kJ/kg, and the energy storage time shows a linear increase relationship with increasing PCM latent heat.

Hygrothermal and energy performance assessment of a passive building wall integrating PCM and bio-based hygroscopic material

Phase change material (PCM) and hygroscopic material (HM) in building walls are promising passive technologies for temperature and humidity regulation, respectively. Integrating the two materials allows for hygrothermal environment regulation and energy savings. However, the joint effect of the temperature dependence of the HM's hygroscopic properties and the location dependence of the PCM's thermal properties has not been mentioned or demonstrated. This study experimentally assessed the hygrothermal and energy performance of a shell enclosed by a PCM-HM wall. Different wall scenarios were proposed to study the effect of the HM, PCM, and PCM's location. The results highlighted the dominance of temperature and the significance of the PCM on performance. For PCM walls, the thermal and hygric inertia were enhanced, the characteristic times of temperature/relative humidity were increased, and the variation was dampened. Under a sinusoidally varying climate, the peak temperature, thermal load, and fluctuations in temperature, relative humidity, and vapor pressure were reduced, and the peak temperature was delayed. Additionally, the repositioning of the PCM further improved the performance. When the PCM was repositioned from the outside to the middle, the temperature, relative humidity, vapor pressure fluctuations, and thermal load were reduced by 25.0 %, 45.8 %, 54.6 %, and 33.1 %, respectively, in warm to hot climates, and by 12.5 %, 63.6 %, 41.9 %, and 66.0 %, respectively, in cold to temperate climates. The PCM properties are important as the PCM in the PCM-middle wall has a higher melt fraction in the solid–liquid state, which utilizes more PCM latent heat energy and improves wall performance.

The effect of PCM on mitigating thermal runaway propagation in lithium-ion battery modules

The main safety issue of lithium-ion batteries (LIBs) is thermal runaway (TR), which has greatly hindered the application of LIBs. Phase change materials (PCM) have been used in battery modules as a thermal management method due to the heat absorption function during the phase change process. However, the role of PCM in TR propagation mitigation has not been carefully examined. In this paper, a 1D heat transfer model was developed to predict the mitigation effect of PCM on TR propagation of a battery array, which shows the superiority of high simulation speed and accuracy. The effects of thermo-physical parameters of PCM on cascading cell-to-cell thermal runaway propagation behavior were investigated. In addition, we gave an optimal range of key parameters of PCM based on safe regulations of China and the United Nations regarding to the TR in electric vehicle LIBs. It was found that the latent heat, density and heat capacity of PCM have similar effects on TR propagation behavior. With the increase of the three PCM parameters, the time duration between cell-to-cell failure propagation increases linearly, which shows a slower TR propagation rate. The optimal ranges for density, heat capacity and latent heat of PCM are over 2150 kg·m−3, over 4100 J·kg−1·K−1 and over 9 × 105 J·kg−1, respectively. What’s more, the TR propagation will exacerbate with the increase of thermal conductivity of PCM, which reminds us to notice a balance between thermal management and TR mitigation in PCM-based thermal management system. Generally, through analyzing the effect of thermal diffusivity of PCM in TR inhibition, we found higher thermal diffusivity will speed up the propagation of TR. And the TR propagation speed is more sensitive to the change of density of PCM. The thermal diffusivity of PCM should be less than 9 × 10−7 m2·s−1 to satisfy the safety standards. The PCM manifests great performance in retarding TR propagation with the phase transition temperature in the range from 318.15 to 518.15 K. Moreover, we found that there exists a critical PCM thickness over which TR propagation will not occur. As the battery thickness increases from 8.8 to 56.5 mm, the critical PCM thickness shows a non-monotonic variation trend (increasing at first and decreasing later). This study demonstrates the feasibility of using PCM as a thermal runaway mitigation strategy and provides a guideline for the optimization of physical parameters of PCM.

Numerical investigations on the absorption of a metal hydride hydrogen storage tank based on various thermal management strategies

This study presents numerical investigations on the performance of the charging process of a metal hydride-based hydrogen storage tank. Three scenarios were developed to examine the absorption performance and compare the effectivenesses of proposed thermal management alternatives. In Scenario-1, the metal hydride (MH) tank is cooled with convective heat transfer on the lateral surface of the tank, i.e., external convection. In Scenario-2, phase change material (PCM) is wrapped around the MH tank to investigate passive thermal management. Scenario-3, a hybrid approach, includes the PCM layer and an internal cooling pipe. In this scenario, the heat transfer fluid (HTF) inside the tube is activated depending on the temperature within the MH tank. An in-house 2D axisymmetric numerical code was developed using the finite volume approach in MATLAB software. In the parametric study, several design parameters and operating conditions were selected, such as (i) charging pressure, (ii) external convective heat transfer coefficient, (iii) PCM thickness, (iv) latent heat of PCM, (v) HTF temperature, and (vi) convective heat transfer coefficient of the HTF, and as a total of 334 parametric analyses were conducted by varying the numerical values of the parameters chosen in wide ranges. The outputs, like spatial and temporal variations of hydride bed temperature and weight fraction, are evaluated for each of the proposed scenarios. As a result, it was observed that the storage performance strongly depends on the convection coefficient at ambient conditions. In Scenario-1, beyond 1000 W/m2K, convective heat transfer coefficient variations do not cause a significant change in the charging process. In Scenario-2, variations in PCM thickness do not cause a considerable change in the storage performance significantly beyond 3 cm. The variations in PCM thickness become important at lower latent heat values and PCM thicknesses less than 2.5 cm. In Scenario-2 and Scenario-3, PCM thickness over 2.5 cm and latent heat of fusion parameter over 150 kJ/kg should be selected to provide a thermal management strategy to be implemented. While the storage criteria were determined according to different thermal management strategies, the PCM thickness and latent heat of fusion parameters showed higher storage performance than the external convection coefficient at the same charging pressure. Temperatures at critical nodes in the MH-PCM system vary depending on location and reaction time. For all thermal management strategies in the hydride bed in positional temperature distributions, the temperature is minimum at the nodes close to the straight pipe. In the scenario-based analysis of the hydride bed temperature, the Scenario-3 thermal management strategy provides the MH bed domain at a lower temperature than Scenario-2. Here, the convection coefficient inside the cooling channel is a critical parameter for the hydride bed temperature.