Latent Heat Of Phase Change Material Research Articles

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.

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.

Protic dialkylammonium-based ionic liquids as promising solid-solid phase change materials for thermal energy storage: Synthesis and thermo-physical characterization

The widespread deployment of renewable energies such as solar and wind implies the parallel development of energy storage systems to deal with their intermittency. Storing renewable energy as thermal energy is one of the alternatives under constant research. In this regard, phase change materials (PCMs) are able to store large amounts of energy at a nearly constant temperature in the form of latent heat. Nevertheless, most of these PCMs undergo solid-liquid transitions, which hamper their implementation due to leaking issues, forcing the need for containment and increasing the final cost of the TES system.Therefore, a class of PCMs possessing solid-solid transitions has emerged to avoid these problems, the so-called organic ionic plastic crystals (OIPCs). Currently, the scientific literature and the number of OIPCs available for TES are rather scarce. Herein, we present the synthesis, the structural, and the thermo-physical characterization of nine OIPCs based on the dioctylammonium cation combined with different organic and inorganic acids as the anions. Particular attention has been paid to the most characteristic thermal properties of PCMs (latent heat, transition temperature, subcooling, thermal conductivity, and energy storage density), evaluating their thermal stability and the reliability of the most promising materials over thermal cycling as well. Among the prepared OIPCs, 3 of them, [DOA][NO3], [DOA][Cl], and [DOA][FOR], exhibited promising properties with remarkable solid-solid transition enthalpies of 156.6 J/g (at 41.4 °C), 101.2 J/g (at 20.0 °C) and 58.4 J/g (at 29.7 °C), respectively. These 3 OIPCs showed high potential to be used and integrated as PCMs in TES systems at temperatures below 45 °C.

Thermal heat transfer and energy modeling through incorporation of phase change materials (PCMs) into polyurethane foam

Decreasing HVAC energy consumption through insulation effectiveness enables low energy use, low carbon emissions, and high thermal comfort in sustainable buildings. PCMs for energy storage are an innovative option, but in buildings, their high thermal conductivity is a concern.The PCM latent heat of fusion and thereby it’s transition temperature has been a key parameter in PCM selection but little is known of the effect of PCM on building energy contributions arising from increasing thermal conductivity (k), density (ρ), and specific heat capacity (Cp). To resolve this, in this paper, two PCMs with transition temperature above and below the outdoor temperature incorporated in highly porous flexible polyurethane foam were evaluated using a one-dimensional (1D) foam core panel built in COMSOL Multiphysics®. The simulations were run using the summer season in a humid subtropical climate zone with an outdoor temperature of 35 °C. It was found that apart from the latent heat of fusion, the combined effects of high ρ and Cp could mitigate the increased k of PU-PCM composites to improve the insulation performance. Building energy modeling using EnergyPlus with the foam core incorporated into a structural insulated panel (SIP), revealed that the use of PCMs regardless of the transition temperature could reduce annual electricity consumption by 15–20%, with a significant amount of energy savings arising from the cooling load in summer.

Effect of two organic phase change materials on the thermal performance of asphalt pavements

ABSTRACT Higher temperature is one of the key reasons for thermal distresses in asphalt pavement. It also adds to the Urban Heat Island (UHI) effect as it influences the near-surface air temperature. To design cooler pavements, phase change materials (PCMs) can be incorporated into asphalt pavements. However, considering the negative effects of PCM leakage on the physical and rheological properties of asphalt binder, a cent-percent effective core-shell encapsulated PCM suitable for asphalt pavement applications was developed under this study. With the incorporation of two organic mixture (OM) based PCMs, i.e., OM-35 and OM-42, a peak decrease in the pavement surface temperature of 3.05 °C and 4.36 °C, respectively were observed under the field condition. Furthermore, from the long-term thermal performance assessment, it was found that the magnitude of temperature reduction depends on the phase change temperature and latent heat of PCM. The season of occurrence of the peak temperature reduction depends on the phase change temperature of the PCM. Due to PCM solidification, the increase in night-time pavement surface temperature was observed to be about half of that during day time. Further, the statistical analysis reveals that the decrease in pavement surface temperature due to PCM incorporation is significant and consistent.

Evaluation and analysis of the improvement in charging time for the high-power fast charging module using phase change material

The advancement of charging time for the fast charging piles facilitates the full adoption of EVs. The benefits of adding the suitable phase change material (PCM) to the thermal control system of the high-power fast charging power module are demonstrated in this experimental study. The effects of different PCM's melting temperature, thermal conductivity, and filling thickness on the improvement of charging time are explored, and the PCM melting rate is visualized to reveal the mechanism of PCM in improving the charging time. The results show that the extension in charging time of 2370 s is found for the charging power module coupled with PCM at the heat generating power of 15 W, and it is extended by 54% and 39% at heat generating power of 25 W and 35 W, respectively. The benefit of applying the PCM in the improvement of charging time for the charging power module is lessened with increasing the air velocity. The optimal PCM melting temperature is 47.5 °C, and it achieves the maximum charging time of 1540 s. The maximum available charging time is 1620 s at the filling PCM thickness of 5.5 mm. Also, the charging time is extended by 510 s when the thermal conductivity of PCM increases from 0.2 W/(m K) to 5 W/(m K). Increasing the heat generating power or decreasing the air velocity will shorten the completed melting time of the used PCM, and the initial melting time is also ahead. A faster PCM melting rate is observed at the lower PCM melting temperature and filling thickness, and this shortens the PCM latent heat role in the thermal control for the charging power module.

Hybrid battery thermal management by coupling fin intensified phase change material with air cooling

Phase change material (PCM) based passive battery thermal management (BTMS) is a promising strategy for controlling lithium-ion battery temperature during operation. However, the drawbacks of low thermal conductivity and poor secondary heat dissipation of PCM still need to be addressed. Herein, the metal fin intensified PCM system coupling with air cooling is proposed for battery thermal management. The effects of PCM thickness, metal fin diameter and number, air inlet velocity, and airflow temperature on the performance of the proposed BTMS are numerically investigated. Results indicate that the novel hybrid BTMS exhibits a superior cooling performance than fin-air BTMS without PCM and PCM-air BTMS without fins, reducing the maximum battery temperature by 18.6% and 3.2%, respectively. The embedded fins can improve the heat dissipation of the battery and PCM. Increasing air velocity can help recover the PCM latent heat but consume additional power. The proposed BTMS is investigated and optimized considering the cooling performance and power consumption tradeoff. The optimal design has a 1.0mm PCM thickness, 162fin numbers, and a 3.0mm fin diameter. Under such an optimal design, battery temperature can be controlled below the desired value of 40°C with less power consumption. The run-out of PCM latent heat is also effectively prevented in continuous cycle operation with an air velocity of 2.0m/s. This study can provide new insights into an advanced BTMS design for next-generation battery systems with high charging and discharging rates.

Performance optimization of metal hydride hydrogen storage reactors based on PCM thermal management

Metal hydrides (MH) are considered promising hydrogen storage materials. In applications, the heat transfer characteristics of MH hydrogen storage reactors are closely related to their storage performance. Phase change materials (PCM) were proven to integrate with MH reactors for effective thermal management. Nevertheless, the PCM based MH reactors (MH-PCM reactors) still need to overcome the heat transfer resistance and the loss of volumetric hydrogen storage capacity caused by the PCM volume proportion. The present work established a mathematical model to describe the transfer and reaction process in the MH-PCM reactor. Various parameters were discussed in the current work. It was found that the increased PCM's amount and latent heat have a restricted effect on the enhancement of heat transfer and absorption reaction rate. The higher PCM's thermal conductivity and hydrogen supply pressure effectively enhanced the heat transfer and reaction rate. Furthermore, the increased absorption pressure can improve PCM's sensible heat storage capacity, which provides a new approach for optimizing PCM consumption. Finally, the quantitative relationship among the volumetric hydrogen storage capacity, the volume fraction and thermophysical properties of PCM, and the absorption pressure were established by systematic analysis, which provides an essential theoretical basis for the optimization of MH-PCM reactors.

Experimental investigation of an alternative battery pack thermal management system

Placing the batteries in PCM (Phase Change Material) filled containers causes a thermal imbalance in the pack because the heat can be dissipated from the sides, but it is accumulated in the center. An alternative geometry is proposed and tested to solve this problem. The thermal performance of the proposed battery pack structure employing PCM has been experimentally studied in free convection conditions. The battery pack is formed by placing 12 test batteries in the same size of 26650 LiFePO4 in custom-designed aluminum (Al 6065) chamber. The single-piece chamber consists of three subchambers connected by straight, rectangular, and parallel fins. The cells are positioned in the 4S3P arrangement. Three different PCMs with different melting temperatures are utilized, and their effect on the battery pack temperature is sought under a stagnant air environment (21 °C). The pack has been tested during discharging at 2C (1.3 W), 3C (2.75 W), and 5C (7.83 W). The heat generation values are adopted from the literature. The maximum temperature in the cells and the maximum temperature deviation between the cells are monitored while the cells are being charged or discharged for different test procedures. Instead of placing PCM and cells in a single case like in studies in the literature, a tailor-made finned geometry helped provide a more homogenous temperature in the cells thanks to the finned structure on the air side. In this way, the maximum temperature difference inside the battery pack is kept below 5 °C for all cases except the extreme case of cyclic 5C discharge/charge analysis with CrodaTherm47. The maximum temperature of the battery pack could be kept below the critical value (60 °C) only when CrodaTherm37 was employed for three consecutive cycles at a discharge rate of 5C/7.83 W as the fin temperatures could be kept at the optimum level, and the PCMs latent heat can be exploited the most.

Investigation on heat transfer enhancement of phase change material for battery thermal energy storage system based on composite triply periodic minimal surface

Phase change material (PCM), such as paraffin wax, has attracted extensive attention in the field of battery thermal energy storage (BTES) system. However, the latent heat of the PCM is unable to be efficiently utilized in the cases with fast thermal responses due to the low thermal conductivity. Triply periodic minimal surface (TPMS) has large surface area. In this study, the composite P-IWP type TPMS is proposed to enhance local heat transfer of the PCM. The thermal performance of the TPMS-based BTES system is studied by simulations and experiments. The results demonstrate that the composite P-IWP type TPMS sheet structure improves the efficiency of the PCM latent heat utilization. The enhanced heat transfer method based on traditional Kelvin type metal foam structure cannot make full use of the latent heat of PCM. Compared with the P type TPMS, the melting time of the PCM in the case of P-IWP type TPMS reduces by 30.8 %. The battery temperature in the case of P-IWP types TPMS decreases by 12.2 % and 11.3 % than that in the case of PCM-only at 1C and 2C discharge rates, respectively. In addition, the experimental results of the cycle process indicate that the TPMS-based BTES system reduces the temperature rise of the battery and increases the duration of the unit temperature drop.

Hybrid PCM-steam thermal energy storage for industrial processes – Link between thermal phenomena and techno-economic performance through dynamic modelling

This study aims to assess the performance and economics of novel hybrid thermal energy storage (HyTES) for industrial applications, linking performance to thermal phenomena occurring within the system. The storage hybridisation concept is based on coupling latent heat storage modules containing high-temperature Phase Change Materials (PCMs) with a fast-response steam accumulator. Such hybrid storage, where heat is stored in both forms of steam and latent heat of PCMs, has the potential to capture excess heat produced by the steam generator of any industrial processes, which can then be used at peak times. HyTES performance is dynamically modelled during charging, idle, and discharging stages. The results show that the HyTES provides 14% extra energy storage capacity than the existing steam accumulator within an identical total volume. Furthermore, the study provides technical analysis of HyTES, and thorough comparison between configurations with different PCM volumes, PCM types and charging times. This is essential to ultimately quantify the whole range of benefit of hybrid energy storage. The sensitivity analysis reveals that Incorporating the HyTES significantly improves energy capacity, and the degree of improvement is mainly affected by the charge duration, approximately 15% after 1 h, and 45% after 4 h of charging. Furthermore, it is shown how the PCM properties affect the performance of HyTES. Finally, the CAPEX and O&M cost of the entire system are assessed in different scenarios and found to be 5% less when HyTES replaces the conventional SA.

Investigation on the dynamic thermal storage/release of the integrated PCM solar wall embedded with an evaporator

The integrated phase change materials (PCM) solar wall can store solar energy effectively, which has a broad application prospect. However, the integrated PCM solar wall cannot completely release heat at night. In this paper, the evaporator of the heat pump system is embedded in the integrated PCM solar wall, which can realize the combination of active and passive utilization of solar energy. A numerical study on the thermal storage/release characteristics of the integrated PCM solar wall with an embedded evaporator was carried out in this paper considering its two-dimensional heat transfer. The effect of the thermal release mode, the thermophysical parameters of PCM and the solar radiation intensity on the thermal storage/release characteristics was studied. The simulation results showed that the active thermal release mode increased the released heat by 33.33 kJ/kg, and the proportion of the released heat to the stored heat increases by 30.12%, compared with the passive thermal release mode. Moreover, the increase of the phase transition temperature and the thermal conductivity of PCM can increase the stored heat and released heat, and the latent heat of PCM will increase the stored heat and decrease the released heat. The conclusion can provide a theoretical basis for the research of active and passive solar systems.

Multi-objective optimization of a phase change material-based shell-and-tube heat exchanger for cold thermal energy storage: experiments and numerical modeling

• PCM-based cold thermal energy storage is numerically and experimentally analysed. • The experimental outcomes show room for optimization in the PCM discharging phase. • Charging/discharging time and heat transfer area/melting difference are optimized. • Multi-objective genetic algorithm allows to exploit up to 72% PCM latent heat. • This optimal solution implies a 69% increase in minimum heat transfer area. In recent years, significantly increasing demand for air conditioning systems has led to higher power consumption during on-peak hours. If optimized, latent heat thermal storage for chiller systems – thanks to its high storage density and compact structure – can reduce installed cooling capacity and allow the chiller to operate more continuously. Starting from the existing design, this work presents a multi-objective optimization framework to improve the storage performance of a phase change material (PCM)-based shell-and-tube heat exchanger. To address this issue – based on experimental data – a 2D axial-symmetric transient numerical model is first developed. To investigate the overall performance of the system – depending on geometrical features and chiller operating conditions – a parametric analysis is performed. Then, by coupling the numerical model developed in COMSOL Multiphysics environment with MATLAB, the system performance is optimized through the genetic algorithm (GA), i.e., minimizing PCM charging/discharging time, by varying the chiller operating conditions. The optimal solution is achieved under a water mass flow rate of 0.095 kg/s, implying a reduction in the inlet temperature of 1.25 °C with respect to the reference case. Results are further validated through experimental tests and discussed looking at the PCM melting and solidification processes for better exploitation of this storage technique. As the main outcome of the model optimization on user’s demand, the maximum amount of PCM that can be fully exploited is equal to 40 % of the initial one. Therefore, based on this value, a further optimization step by GA is performed to define the minimum heat transfer area, resulting in a shell diameter reduction of 12 cm to exploit 72 % of the PCM potential.