Phase Change Material Heat Sink Research Articles

Effect of Source-Sink Misalignment and Sink Cavity Aspect Ratio on the Thermal Performance of Gallium Heat Sinks

Herein, we numerically investigated methods to improve heat dissipation from the base of a phase-change material (PCM) heat sink exposed to high heat flux (15 W/cm2). The sink cavity exhibited a rectangular cross-section with two opposite vertical walls of high thermal conductivity. These walls serve as heat-dissipating fins. We used gallium, a metallic PCM with high thermal conductivity and a low melting point to improve heat dissipation by leveraging buoyancy-driven circulations within the molten gallium. We adopted a method to position the sink base on top of the heat source surface in such a way to augment temperature gradients within the liquid to induce imbalances in gallium density and consequent internal circulations. In this technique, one vertical wall is subjected to forced-convective heat exchange with the surroundings, while the other remains adiabatic. Subsequently, for the case which showed optimum performance, we relaxed the adiabatic thermal boundary condition applied at one of the vertical walls and replaced it with convective heat transfer condition, and assessed the sink performance based on that. Further, we analyzed the impact of various aspect ratios of the sink cavity on the induced internal circulations and base cooling. Sink cavities with aspect ratios of 1.33, 0.96, and 0.64 corresponding to sink heights of 20, 17, and 14 mm, respectively, were examined under a consistent heat flux applied across a 15-mm base length. We also investigated the precise positioning of the sink base relative to the heat source surface and explored its influence on temperature gradients and gallium density imbalances crucial for induced internal circulations. Results indicate that a sink cavity aspect ratio of 0.96 yields the optimal heat dissipation from the base. Further, aligning the left bottom edge of the sink base with the left edge of the heat source surface maximizes heat dissipation to the ambient surroundings, thereby prolonging latent-heat dumping into the sink before the gallium completely melts. Any misalignment between the sink base and the surface of the heat source may have a profound impact on the temporal evolution of induced internal circulations within the molten gallium, essentially affecting heat dissipation from the sink base.

Numerical thermal analysis and structural optimization of cascaded PCM heat sinks for thermal management of electronics

In the present study, an innovative cascaded phase change material (PCM) heat sink using organic PCMs was proposed for electronic thermal management. The design arranges multiple PCMs with progressively lower melting points along the heat transfer path, allowing active control of the melt front. A numerical model with 5 % accuracy was developed to evaluate thermal performance. Based on the validated model, the effects of PCM stage numbers, PCM volume fractions, fin types, and fin volume fractions were analyzed. The fin volume fractions were further optimized using a support vector machine (SVM) and genetic algorithm (GA) methods. Results showed that a three-stage PCM heat sink with pin fins and increasing configurations outperformed single-stage PCM heat sinks, enhancing heat transfer by up to 36.7 %. Additionally, the innovative cascaded PCM heat sink with a uniform 20 % fin volume fraction across the three stages achieved a 38.8 % improvement compared to single-stage configurations. When the fin volume fractions were set to 24.1 %, 17.6 %, and 13.0 % for the three stages, thermal performance of the innovative cascaded PCM heat sink was enhanced by up to 39.8 % compared to single-stage configurations. The findings provide valuable insights for the design and application of PCM-based thermal management systems, potentially leading to more efficient solutions for various engineering fields.

Assessment of Thermal Management Using a Phase-Change Material Heat Sink under Cyclic Thermal Loads

Phase-change materials (PCMs) are widely used in the thermal management of electronic devices by effectively lowering the hot end temperature and increasing the energy conversion efficiency. In this article, numerical studies were performed to understand how temperature instability during the periodic utilization of electronic devices affects the heat-dissipation effectiveness of a phase-change material heat sink embedded in an electronic device. Firstly, three amplitudes of 10 °C, 15 °C, and 20 °C for fixed periods of time, namely, 10 min, 20 min, and 40 min, respectively, were performed to investigate the specific effect of amplitude on the PCM melting rate. Next, the amplitude was fixed, and the impact of the period on heat sink performance was evaluated. The results indicate that under the 40 min time period, the averaged melting rate of PCMs with amplitudes of 20 °C, 15 °C, and 10 °C reaches the highest at 19 min, which saves 14 min, 10 min, and 8 min, respectively, compared with the constant input of the same melting rate. At a fixed amplitude of 20 °C, the PCM with a period of 40 min, 20 min, and 10 min has the highest averaged melting rate at 6 min, 11 min, and 19 min, saving the heat dissipation time of 3 min, 8 min, and 14 min, respectively. Overall, it was observed that under identical amplitude conditions, the peak melting rate remains consistent, with longer periods resulting in a longer promotion of melting. On the other hand, under similar conditions, larger amplitude values result in faster melting rates. This is attributed to the fact that the period increases the heat flux output by extending the temperature rise, while the amplitude affects the heat flux by adjusting the temperature.

Design and performance assessment of a solar photovoltaic panel integrated with heat pipes and bio-based phase change material: A hybrid passive cooling strategy

This study investigates the effectiveness of an indirect passive cooling solution for photovoltaic (PV) panels using flattened heat pipes (FHPs) and phase change material (PCM). An innovative passive cooling design is proposed to cool a PV panel using multiple FHPs with a thin graphite sheet between the PV panel and the FHPs. Five experimental cases are examined under varying heat flux loads. Case O serves as the baseline with no cooling system, while Cases 1 to 4 feature different configurations of FHPs and aluminum sheets, with PCM heat sinks added in Cases 2 and 4. The investigation focuses on temperature profiles, temperature reductions, and final temperatures of the PV panel, especially at the end of a 4-hour experimental period when the PCM is fully melted. The results show significant temperature reductions in Case 1 compared to the baseline, with further improvement in Case 2 due to the PCM heat sink. Temperature reductions in Cases 2 and 4 are consistently higher than in Cases 1 and 3, demonstrating the enhanced cooling potential of PCM. Case 4 achieves the highest temperature reduction of 37.0 °C, followed by Case 2 with 34.9 °C under a radiative heat flux of 1000 W/m2. Using 4 FHPs (Cases 1 and 2) is economically justified, offering comparable cooling performance to 8 FHPs (Cases 3 and 4), thus ensuring cost-effectiveness and reducing material usage by over 50 %. A maximum enhancement in PV electrical efficiency of 17.3 % is achieved in Case 2 during PCM phase change with a radiative heat flux of 1000 W/m2.

Thermal management and heat transfer enhancement of electronic devices using integrative phase change material (PCM) and triply periodic minimal surface (TPMS) heat sinks

This study focuses on the thermal management of electronic components using phase change materials (PCM) with triply periodic minimal surface (TPMS) structures. Three PCM-TPMS heat sinks (PCM-Gyroid, PCM-IWP, and PCM-Primitive) are examined, compared to pure PCM heat sinks. The heat sinks are evaluated under pulsed power sources with passive and active cooling. The effect of varying TPMS relative densities (10 %, 20 %, and 30 %) is also analyzed. The results indicate that PCM-TPMS heat sinks significantly accelerate the melting interfaces of PCM and provide improved heat transfer paths. They effectively scatter and reduce the base temperature of electronic components, with average values of 61.9 °C and 34.9 °C, compared to higher temperatures for pure PCM heat sinks under passive and active cooling, respectively. Increasing the relative density of TPMS structures from 10 % to 30 % leads to a slight improvement in base temperature reduction for the different TPMS structures. Among the three TPMS configurations, the PCM-Gyroid heat sinks are found to be the most effective in reducing base temperatures compared to PCM-IWP and PCM-Primitive heat sinks. Additionally, the use of PCM-TPMS significantly enhances the reliability and durability of electronic components by mitigating thermal cycling. Overall, the study demonstrates the potential of PCM-TPMS heat sinks in improving the thermal management and performance of electronic components.

Design and performance assessment of a triply-periodic-minimal-surface structures-enhanced gallium heat sink for high heat flux dissipation: A numerical study

This study numerically investigates a phase-change material heat sink using gallium and Primitive Triply Periodic Minimal Surface (TPMS) cells structure as in-fill for applications requiring high heat-flux dissipation, e.g., electronics. Initially, we used only gallium without thermal conductivity enhancers, relying solely on buoyancy-driven circulations of melted gallium for the convective cooling of a hot sink base. However, this study aims to surpass gallium’s innate heat-dissipation capability. Therefore, the sink is enhanced with a high conductivity Primitive TPMS cells structure. Hybridization of conduction and convection heat dissipation enhancements is accomplished by using only one layer of the TPMS cells installed at the hot sink base. Comparison with the full TPMS structure filling option is made. In the full TPMS structure filling option, the sink relies mainly on conduction through the TPMS structure’s body and less on natural convection. However, equipping the sink with TPMS structures reduces the overall latent heat storage capacity. Therefore, additional gallium is added to the sink to match the overall gallium content in the baseline case without TPMS structures. Furthermore, the effect of the boundary conditions applied at the wall is explored. The results show considerable improvements in heat dissipation and peak temperatures with the TPMS cells, where by the time 100 s (about 20 s post complete melting) peak temperatures are about 13 percent lower than in the case without TPMS structures. Furthermore, the full structure filling option demonstrates superior performance over the partially filled ones, highlighting the importance of conduction through TPMS cells over convection in the free gallium space. Unlike the partial filling option, conduction in the full filling option has a continuous favorable impact on heat dissipation from the onset of the heating process.

3D transient numerical analysis of PCM dendritic cylindrical heat sinks designed by constructal theory

The phase change material (PCM) heat sink represents an important cooling tool for many applications. The presence of a heat sink in devices requires additional space to occupy it. This led to modeling this space to obtain the highest thermal performance with the smallest size. Among the modern modeling methods is constructal theory. This work presents a numerical modeling of the performance of cylindrical phase change material heat sinks with branched heat transfer fluid tubes in the manner of arterial and venous according to constructal theory. The aim of numerical simulations is to demonstrate the effect of growth in design by increasing the number of branches on thermal performance and melting time and the extent to which this is reflected in pressure drops. Several branching configurations are studied for comparison purpose. The governing continuity, momentum and energy equations were solved using the computational fluid dynamics method. Three-dimensional transient simulations of the melting process of phase change materials were performed using an enthalpy and porosity model. Four combinations of constructal dendritic tubes were considered. The results show that the proposed dendritic PCM heat sink significantly reduces the melting time of PCM compared to the traditional heat sink consisting of a shell and single tube up to 69.1 %. The drop in heat transfer fluid temperature at the outlet decreased by up to 51.7 %. The results proved also the heat transfer enhancement is governed with pressure drop increase because of changing branches configuration. Finally, this paper demonstrated the ability of constructal theory to provide promising solutions for cylindrical heat sinks of phase change materials in various applications.

Long-Lasting Heat Dissipation of Flexible Heat Sinks for Wearable Thermoelectric Devices.

Flexible wearable thermoelectric (TE) devices hold great promise for a wide range of applications in human thermal management and self-powered systems. Currently, the main challenge faced by flexible TE devices is the inadequate dissipation of heat, which hinders the maintenance of significant temperature differences over prolonged periods. Most existing heat sinks, being rigid in nature, compromise the overall flexibility of the device. Therefore, the challenge lies in maintaining device flexibility while ensuring effective heat dissipation. In this study, we developed a flexible phase-change material (FPCM) heat sink to address this issue and enhance the heat dissipation capabilities of TE devices (FPCM-TED). When used as a thermoelectric cooler (TEC), the FPCM heat sink efficiently absorbs heat from the hot end, enabling long-lasting and high-performance cooling of the TEC. This capability effectively reduces body temperature by up to 11.21 °C and can be sustained for at least 300 s. Additionally, when employed as a thermoelectric generator (TEG), the FPCM absorbs heat at the cold end, thereby increasing the temperature difference between the hot and cold ends and enhancing the output performance of the device. By integrating FPCM-TED into a fabric wristband, we successfully developed a self-powered wireless pedometer sensing system. This breakthrough lays a solid foundation for the application of wearable, smart clothing.

Waste heat management in electric motors using thermoelectric generator integrated with phase change material and metal foam-embedded heat sink

The waste heat management process from various thermal sources is associated with promising results in the energy conversion field. Thermoelectric generators integrated with phase change materials containing metal foams are useful means for recovering waste heat and converting it into electrical energy. Installing these hybrid cases on common heat sources and providing a practical strategy for waste heat management addresses a significant research gap in this field. The aim of this study is to manage waste heat from a three-phase asynchronous electric motor of a milling machine for the first time using a novel prototype thermoelectric system. Four thermoelectric modules (connected electrically in series) with zero-cooling energy phase change material and copper foam heat sink were embedded on the motor body. Hence, continuous and fluctuating loads were imposed on the motor, starting from ambient temperature. This caused the motor body to heat up and transfer the wasted heat to the module and the environment. The results of this study show that the proposed system was successfully started via the waste heat of the motor body. Thermal energy was absorbed from the hot side of the module, and the hybrid heat sink controlled the temperature of the cold side. Moreover, an appropriate temperature difference was provided across the module, and the system produced electricity for a long time during milling operation. The maximum output voltage in constant and periodic loads, with on/off durations of 180 s and 360 s, was recorded as 960 mV, 1280 mV, and 1440 mV, respectively. The mentioned hybrid thermoelectric system provides a unique solution for waste heat management in industrial applications, improving economic savings.

Experimental study on a rectangular evaporator loop heat pipe with a phase-change material heat sink

To satisfy the heat dissipation requirements of high heat flux electronic devices in extreme conditions where no suitable heat sink exists, such as in the flight process of hypersonic aircraft and the re-entry process of spacecraft, a rectangular evaporator loop heat pipe (LHP) with a phase-change material heat sink was designed and developed. Extensive experimental studies on the thermal control performance of the LHP have been performed, mainly including the startup performance, maximum temperature control time, dynamic response to varying heat load, and the heat transfer limit. Experimental results showed that the LHP could successfully realize the startup at a small heat load as low as 5 W. Under 100 W heat load, the LHP can keep operating for 4 h and 16 min at most with the operating temperature lower than 50 °C, including 2 h and 40 min of quasi-stable operation. The heat transfer limit of the LHP could reach up to 200 W, corresponding to a heat flux of 13.3 W/cm2 at the evaporator. In addition, the LHP exhibited excellent dynamic response characteristics to varying heat loads, holding great application potential in future thermal control tasks in extreme conditions.

Optimizing Waste Heat Conversion: Integrating Phase-Change Material Heatsinks and Wind Speed Dynamics to Enhance Flexible Thermoelectric Generator Efficiency.

Flexible thermoelectric generators (FTEGs) have garnered significant attention for their potential in harnessing waste heat energy from various sources. To optimize their efficiency, FTEGs require efficient and adaptable heatsinks. In this study, we propose a cost-effective solution by integrating phase-change materials into FTEG heatsinks. We developed and tested three flexible phase-change material thicknesses (4 mm, 7 mm, and 10 mm), focusing on preventing leaks during operation. Additionally, we investigated the impact of wind speed on the output performance of FTEGs with a flexible phase-change material heatsink. The results indicate that the appropriate flexible phase-change material thickness, when integrated with considerations for wind speed, demonstrates remarkable heat-absorbing capabilities at phase-change temperatures. This integration enables substantial temperature differentials across the FTEG modules. Specifically, the FTEG equipped with a 10 mm thick flexible phase-change material heatsink achieved a power density more than four times higher when the wind speed was at 1 m/s compared to no wind speed. This outcome suggests that integrating phase-change material heatsinks with relatively low wind speeds can significantly enhance flexible thermoelectric generator efficiency. Finally, we present a practical application wherein the FTEG, integrated with the flexible phase-change material heatsink, efficiently converts waste heat from a circular hot pipe into electricity, serving as a viable power source for smartphone devices. This work opens exciting possibilities for the future integration of flexible thermoelectric modules with flexible phase-change material heatsinks, offering a promising avenue for converting thermal waste heat into usable electricity.

Experimental and numerical study on temperature control performance of phase change material heat sink

With the increasing power consumption of electronic products, the rising temperature leads to the deterioration of working environment and the reduction of service life. In order to control the temperature rise of electronic products, in this paper, the heat sinks with phase change material (PCM) and honeycomb metal were designed. And their performance was compared with that of the original heat sink (without PCM and honeycomb metal) then studied under various working conditions. Paraffin (n-eicosane) and prepared low melting point alloy were filled into the heat sink with honeycomb metal. The temperature control performance of heat sink was tested experimentally under different heating power. A two-dimensional heat transfer mathematical model of honeycomb metal PCM heat sink was established and solved numerically. The numerical results were compared with experimental data to verify the mathematical model. The results demonstrate that PCM heat sinks effectively controls the temperature of electronic devices and the low melting point alloy makes heat sink better performance than paraffin. Honeycomb metal further decreases the temperature of the paraffin heat sink by up to 3.6 °C, and extends the effective working time of the alloy heat sink by 14 %. The performance of the low melting point honeycomb metal heat sink is superior to that of the paraffin honeycomb metal heat sink at high heating power, and is close to the latter at low heating power. The effective working time of PCM honeycomb metal heat sink is significantly extended when the PCM melting point is close to the limit temperature, especially at high heating power and for the PCM with low thermal conductivity. This study provides valuable reference for temperature control design of electronic products.

Effect of fin geometry on the thermal performance of a phase change material heatsink

This paper presents an experimental and computational study to optimize a novel folded fin phase change material (PCM) heatsink. An experiment was conducted on a custom heatsink assembly. The results were used to validate a finite element model created in ANSYS fluent. This model utilized solidification/melting calculations in Fluent to study the thermal performance of the heatsink assembly with an applied power ranging from 16 to 48 W, varying fin gaps between 2.32 and 5.52 mm, and fin wall thickness of 0.8–2.4 mm. This study revealed that the proposed fin design provides increased thermal effectiveness for applied power up to 48 W. It was also found that that a fin wall thickness of 0.8 mm increased the time required to fully melt the PCM by 17% compared to the 2.4 mm thick fins. A fin gap of 5.52 mm resulted in an 11% increase in melt time when compared to the smallest gap studied of 2.32 mm.

Gaussian process optimization of phase change material heat sink design

Thermal management strategies based on phase change materials (PCMs) offer promising alternatives to conventional approaches, owing to their ability to absorb transient heat flows by melting. However, the design of PCM heat sinks is challenging due to the nonlinear interactions between heat flow and phase change during melting and solidification. This paper presents the design optimization of PCM heat sinks using a Gaussian Process (GP) method. We show that the GP method offers a significant decrease in computational intensity compared to conventional approaches used for optimization. We apply our method to optimize the design of a PCM-integrated heat sink for a gallium nitride (GaN) device that operates under a pulse train heat profile. Field’s metal-infused copper foam is used as the PCM. We used a reduced order model (ROM) for the PCM-integrated device, which is validated through experimental measurements and finite element simulations. We coupled the ROM with the GP optimizer to determine PCM heat sink design parameters, including geometric dimensions and the composition of the composite PCM, which minimizes both the GaN maximum junction temperature and junction temperature swing. We tested the GP optimizer under various conditions, encompassing GaN device power levels ranging from 1 to 4 W, pulse widths spanning 1 to 10 s, and duty cycles ranging from 10 to 90%. The GP optimizer produced nearly identical results to particle swarm optimization, with a mean absolute error <0.2 °C for optimal thermal performance and a reduction in computational time of 39×. Overall, our design method offers a computationally efficient approach to optimizing PCM-integrated heat sinks for the transient thermal management of electronic devices.

Effect of T-shaped fin arrangements on the temperature control performance of a phase change material heat sink

The control of operating temperature in phase change material (PCM) heat sinks is restricted by their low thermal conductivity. The present study proposes a novel T-shaped fin strategy, targeting to improve the thermal management capability of PCM heat sinks in the field of electronic devices, i.e., the originality behind is that heat flux from the heated surface can be transported to the solid phase region by T-shaped fins over a longer distance. Based on the background of photovoltaic cell thermal management, a numerical calculation was conducted to investigate the temperature control performance of PCM heat sinks with different T-shaped fin layouts, which was compared with heat sinks without fins and with rectangular fins. The key discoveries indicate that the melting front in the heat sink cavity was severely influenced by the fins, which first suppressed and then enhanced natural convection in the melting process and improved the PCM temperature uniformity. Compared to the unfinned and rectangular fin systems, the employment of T-shaped fins could reduce melting time respectively by up to 25.5% and 14.5% (achieved by case 8), and lower wall temperature respectively by maximum values of 18.9 °C and 4.9 °C (obtained by case 12).

The impact of different fin configurations and design parameters on the performance of a finned PCM heat sink

This work builds on our recent research on finned phase change material (PCM) heat sinks, where we proposed a novel Gallium based PCM heat sink concept that counter-intuitively incorporated fins detached from the hot sink base instead of being fully attached to it. The detached and fully attached fin configurations studied utilized the same overall fin size and material resources. The attached fin approach offered less outer fin surface area exposed to the ambient surroundings and less PCM capacity compared with the detached fin approach. However, the attached fin approach facilitated a more direct path for the heat dissipation into the ambient surroundings via the fin body. As an extension of the previous work, the present work explores finned heat sinks that combine the advantages of the above two approaches. First, we present results for two limiting baseline cases of the two finning categories: attached fins with lower outer fin surface area and less PCM and detached fins with a larger exposed fin area and more PCM. Next, we study a heat sink case with attached fins tall enough to have a total outer fin surface area equivalent to the outer surface area of the detached fins case but with less PCM content. Subsequently, we consider cases of fully attached fins with the same total outer fin area and the same total PCM capacity as the detached fins baseline case. Here, we achieve the same PCM content in the sink while still having fully attached fins simply by increasing the overall heat sink size to accommodate additional PCM. This is done in two ways: (1) by expanding the heat sink size in the horizontal direction (i.e., increasing the heat sink width) at constant heat sink height, and (2) by expanding the heat sink height at constant heat sink width. In this work, we propose the best way to utilize the resources in terms of used PCM and used fin content in the heat sink space to achieve the ultimate goal of attaining lowest peak temperatures.

A novel method to improve the performance of PCM thermal energy storage units using a small oscillator plate-numerical analysis

Employing a small oscillator plate is proposed as a novel idea to improve the performance of phase change material (PCM) based thermal energy storage unit. This idea could make mixing heat flow toward the PCM solid-liquid interface to hasten the melting and heat transfer rates. Opposite to the vibration of the whole PCM heat sink suggested in the literature, it needs very slight mechanical energy for oscillation. The oscillator plate was installed at three positions for the horizontal and vertical PCM heat sink: i) the middle of the hot plate, ii) the bottom of the hot plate, and iii) the corner of the heat sink. A computational fluid dynamics model has been employed to model the PCM melting process and evaluate the induced mixing heat flow and its effect on natural convection. A new mechanical method using vibration energy accelerates heat flow to improve heat transfer and thermal energy absorption. The results reveal that in the best case with transversal oscillation at the corner of the heat sink, the melting rate and heat transfer rate (Nusselt number) increase by 39 % and 64.2 % compared to no vibration case, respectively. Also, the absorbed heat energy rate (AHR) within the PCM heat sink is elevated from 0.51 to 0.79 (54.9 %), while the oscillator just consumed as small as 438 mJ of mechanical energy, reflecting this mechanical approach's uniqueness.

Three-dimensional Lattice Boltzmann study on structure optimization and heat dissipation performance of pin-fin heat sink integrated with phase change material

Phase change material (PCM) cooling is an excellent approach for reducing the excessive temperature of electronic devices. However, the heat transfer capacity of a heat sink is diminished by the low thermal conductivity of a PCM. Although this issue can be ameliorated by using extended pin-fins and nanoparticles, the latent heat storage capability of a PCM is decreased. To optimize the heat transfer efficiency of PCM heat sink with pin-fins, in this study, the effects of pin-fin shapes (circle, triangle, square, pentagon, hexagon, and octagon), novel arrangements with triangular fins, and the volume fraction of nanoparticles are investigated using the 3D enthalpy-based multi-relaxation time lattice Boltzmann method. The results showed that the PCM heat sink with triangular pin-fins exhibited optimal thermal performance due to the largest heat transmission area between the PCM and pin-fins. After conducting optimization research on triangular pin-fin arrangements, the full melt time was shortened by 14.3 % and the heat dissipation power was increased by up to 15.2 %, when compared with the PCM heat sink with triangular pin-fins. Furthermore, nanoparticles with a volume fraction of <0.1 were beneficial for balancing the elevated heat dissipation capacity and reducing the latent heat duration of the nano-enhanced PCM.

Flexible Thermoelectric Devices with Flexible Heatsinks of Phase-Change Materials and Stretchable Interconnectors of Semi-Liquid Metals.

Flexible thermoelectric (TE) devices offer great potential for wearable thermal management and self-powered systems, but heat dissipation and electrical interconnection remain key challenges. In this study, we address these issues by integrating flexible TE devices with phase-change material (PCM) heatsinks and stretchable semi-liquid metal (semi-LM) interconnectors. The effectiveness of PCMs with varying melting points for temperature regulation in different environmental conditions is demonstrated, delivering cooling effects exceeding 10 °C. Furthermore, the utilization of semi-LMs instead of LMs enables excellent stretchability and efficient heat dissipation. Moreover, the TE devices generate power with a density of 7.3 μW/cm2 at an ambient temperature of 22 °C, making it an ideal power source for a wearable self-powered sensing system. Successful integration into garments and armbands confirms the practicality and adaptability of these flexible thermoelectric devices, establishing them as critical components for future wearables with superior resilience to daily wear and tear.

Phase change heat transfer in a vertical metal foam-phase change material thermal energy storage heat dissipator

A metallic foam heat dissipator for cooling electronic components was addressed. A heat dissipator is a partitioned aluminum container loaded along with aluminum metallic foam and saturated with paraffin wax. A heat flux at a surface contains a basic uniform flux and the step transient raise, which should be managed by a heat dissipator and a Phase Change Material (PCM). The regulating equations for a melting/solidification transfer of heat & momentum transport in a heat dissipator were instituted into a structure of partial differential equations. Then, the vital monitoring equations were converted into a general dimensionless type and solved by the Finite Element Method. A mesh adjustment technique & automated time-step control was employed to control the accuracy & convergence of the result automatically. An adaptation technique controls the mesh resolution at the melting/solidification interface. The dimensionless temperature of fusion is a vital factor in the control of the surface temperature and heat dissipator efficiency. Considering a fixed amount of material for walls, a heat dissipator with thick sidewalls and thin top and bottom walls results in slightly better thermal performance. Using a PCM heat sink could reduce the heated surface temperature by >175 % during the pulse load.