Search

Strong metal-support interaction (SMSI), namely the strong electronic and structural interaction between metal nanoparticles and supports, one of the most typical synergetic catalytic effects in composite catalysts, has been found critically important in the design of catalyst for thermocatalysis in the past. Recently, however, important and great progress of SMSI-based synergetic effects has been made in electrocatalysis, such as electrocatalyst design and electrocatalytic mechanism investigations. To better understand the nature of the synergetic effect assisting the further development of electrocatalysts, a comprehensive and in-depth overview highlighting and discussing the recent advances of SMSI in electrocatalysis is necessary and highly desirable but still absent. Herein, this review firstly presents various strategies of designing and constructing composite catalysts featuring SMSI. Further from the perspectives of electrocatalysis, the characterization techniques towards the electron structure, local interfacial and morphological features and active sites for SMSI-based electrocatalysts, have been summarized in detail. Importantly, the recent advances in the design of single- and bi-functional electrocatalysts [ABSTRACT FROM AUTHOR]

Zero-sodium-excess solid-state batteries (ZSBs) are promising to overcome the disadvantage of low energy density for Na-ion batteries, but the interfacial issues between the solid-state electrolytes and current collectors remain bottlenecks for their practical applications. Herein, we report a self-regulated stratification of the artificial interphase through the conversion reaction between MgF2 modification layer and Na metal. Ascribed to the huge adsorption energy difference between Al-Mg and Al-NaF, the sodiophilic Mg concentrated at the bottom side and served as the nucleophilic seed for Na, while sodiophobic NaF on the top side provided high thermodynamic stability for Na dendrite and side reaction suppressions. Consequently, the as constructed ZSBs with Na3V2(PO4)3 cathode exhibited prominent energy density of 254.4 Wh kg-¹ (calculated based on the total mass of electrode and electrolyte) with a capacity retention of 82.7% over 350 cycles. This work paves a feasible way to achieve high performance and stable ZSBs. [ABSTRACT FROM AUTHOR]

The pairing of lithium metal anode (LMA) with Ni-rich layered oxide cathodes for constructing lithium metal batteries (LMBs) to achieve energy density over 500 Wh kg-¹ receives significant attention from both industry and the scientific community. However, notorious problems are exposed in practical conditions, including lean electrolyte/capacity (E/C) ratio (< 3 g (Ah)-¹), high cathode mass loading (> 3 mAh cm-²), and low negative/positive (N/P) ratio (< 3), which creates a significant disparity between the current performance of LMBs and the desired requirements for commercial applications. In the review, we present a summary of the recent achievements made in understanding the mechanistic degradation of LMA, followed by practical strategies that are utilized to address these issues. We also consider the detrimental issues of Ni-rich layered oxide cathodes. Furthermore, we highlight current progresses in the field of practical LMBs in coin/pouch cells to stimulate further innovation. In the end, we propose the issues and prospects for development from the perspective of practical LMBs. [ABSTRACT FROM AUTHOR]

Developing advanced nanocomposite phase change materials (PCMs) integrating zero-energy thermal management, microwave absorption, photothermal therapy and electrical signal detection can promote the leapfrog development of flexible wearable electronic devices. For this goal, we propose a multidimensional collaborative strategy combining two-dimensional (2D) MXene nanosheets with metal-organic framework-derived onedimensional (1D) carbon nanotubes (CNTs) and zero-dimensional (0D) metal nanoparticles. After encapsulating paraffin wax (PW) in three-dimensional (3D) networked multidimensional MXene/CoNi-C, the resulting composite PCMs exhibit excellent thermal energy storage capacity and long-term thermally reliable stability. Benefiting from the synergistically enhanced photothermal effects of CNTs, Co/Ni nanoparticles and MXene, PW@MXene/CoNi-C can capture photons efficiently and transfer phonons quickly, yielding an ultrahigh photothermal conversion and storage efficiency of 97.5%. Additionally, PW@MXene/CoNi-C composite PCMs exhibit high microwave absorption with a minimum reflection loss of -49.3 dB at 8.03 GHz in heat-related electronic application scenarios. More attractively, the corresponding flexible phase change film can simultaneously achieve thermal management and electromagnetic shielding of electronic devices, as well as photothermal therapy and electrical signal detection for individuals. This functional integration design provides an important reference for developing advanced flexible multifunctional wearable materials and devices. [ABSTRACT FROM AUTHOR]

The miniaturization of electronic devices has led to an increase in power density and functional integration, resulting in rapid heat accumulation that adversely affects operational stability and service life. Dielectric composite films with excellent thermal conductivity and insulating properties are highly desired for addressing thermal management issues in electronic packaging applications. Hexagonal boron nitride (h-BN) is a promising filler for such composites due to its outstanding thermal conductivity, insulating properties, and chemical stability. However, the inherent platelike structure of h-BN causes significant anisotropy and poor miscibility with polymers, limiting the uniform conduction of heat. This study proposes a high-temperature sintering method that transforms flaky h-BN plates into irregular multifaceted particles. This transformation reduces thermal anisotropy and creates uniform heat conduction pathways. The resulting sintered BN/Epoxy (s-BN/EP) composite films exhibit exceptional thermal conductivity, with in-plane thermal conductivity increased by 36 % to 6.0 W m−1 K−1 and through-plane thermal conductivity increased by 39 % to 1.2 W m−1 K−1 compared to pristine h-BN/epoxy composites. Moreover, s-BN/EP films could maintain low dielectric constant (D k , 3.22) and dielectric loss (D f , 0.015) at 5 GHz. This innovative approach provides a significant advancement in the development of high-performance insulating polymer composites, offering a promising solution for thermal management in high-power-density electronic packaging. [Display omitted] [ABSTRACT FROM AUTHOR]

Highlights Maintaining uniform dispersion of nano filler under high content is critical for fabricating polymer‐based composites with great mechanical and thermally conductive properties. In this work, BNNS/PA12T nanocomposite with the highest boron nitride nanosheet (BNNS) content of 23.1 wt% was successfully prepared by the aqueous solution‐assisted in‐situ polymerization method. Results demonstrate that the BNNS can be uniformly dispersed in the composite due to the low viscosity during the polymerization process. As a result, when the content of BNNS is 23.1 wt%, the mechanical properties and thermal conductivity of BNNS/PA12T nanocomposite are 62 MPa and 1.55 W/(m·K). Furthermore, the composites also possess excellent high‐temperature resistance with the coefficient of thermal expansion (CTE) of 60 ppm/°C, about one third of pure PA12T, and the thermal deformation temperature also reaches 139.4°C. Therefore, the fabricated BNNS/PA12T nanocomposite can be effectively applied as thermal management and packaging materials for electronic devices. BNNS/PA12T nanocomposites were prepared by aqueous solution‐assisted method. BNNS can be uniformly dispersed at the filling content up to 23 wt%. The thermal conductivity of BNNS/PA12T nanocomposite can reach 1.55 W/(m·K). Possessing excellent mechanical properties and dimensional stability. The nanocomposite can be effectively applied for thermal management. [ABSTRACT FROM AUTHOR]

In the rapidly advancing field of 5G technology, efficient thermal management is essential for enhancing the performance and reliability of high-power-density integrated circuits (ICs). This paper introduces an innovative approach to cooling these critical components, significantly surpassing traditional methods. Our design optimizes heatsink and fan configurations through systematic experimentation, varying fin shapes, heatsink dimensions, and fan speeds. The results demonstrate that fan velocity is the most critical factor in reducing IC temperatures, as increased airflow dramatically lowers thermal output. Expanding the heatsink surface area further improves heat dissipation by enhancing airflow interaction, while a larger copper heatsink boosts thermal conduction, effectively reducing the final IC temperature. These optimizations streamline the cooling process, minimizing the need for more complex and expensive equipment. This research sets a new benchmark in thermal management, fostering the development of more efficient and reliable electronic systems in the era of advanced wireless communications. Our approach brings a new dimension to existing research by focusing on the optimization of heatsink and airflow designs specifically for ICs. While previous studies have explored broader thermal management strategies, our work addresses specific challenges in heat dissipation by refining geometric configurations and fan speed adjustments. These optimizations result in measurable improvements in both efficiency and scalability, particularly within the context of high-power 5G systems. [ABSTRACT FROM AUTHOR]

An experimental investigation was carried out on high porosity metal foams subjected to array jet impingement with an objective to develop enhanced heat transfer configurations. In this study, we propose an integrated thermal management system (TMS) aimed toward leveraging the conjugate heat transfer capabilities of target plate, metal foam, and the jet plate--all made from aluminum and assembled such that a proper contact between them can be established. Steady-state heat transfer experiments were carried out for 10 and 20 pores per inch (PPI) aluminum foams of 0.93 porosity. Both metal foams were 12.7-mm thick. The normalized jet-to-jet spacing was varied from 2 to 12 times the jet diameter, while the jet diameter was fixed. The ratio of the jet plate thickness and jet diameter (nozzle aspect ratio) was 6.35, which ensured proper development of jets inside the nozzles. Experiments were conducted over a wide range of Reynolds number (based on jet diameter) varied from 100 to 5000. The obtained convective heat transfer coefficient for different configuration was evaluated in context with pressure drop. The analysis of experimental results reveal that large open area ratio jets combined with high porosity metal foams provide highly efficient and high-performance cooling for the investigated range of Reynolds numbers. [ABSTRACT FROM AUTHOR]

The wide spread adoption of heat pipes in automotive and aviation application is hampered by the fact that they require protection against frost damage caused by the repetitive exposure to subzero temperatures. Here, we present heat pipe with ethylene glycol and water as working fluid that can prevent damage to the copper container on exposure to cyclic freezing and thaw. In this research, different mass concentrations of water and ethylene glycol have been tested for freeze protection of heat pipes. Experimental investigations have shown that 3.5% by mass concentration of ethylene glycol in water is able to sustain the cyclic freezing and avoid any damage to the copper pipe. In this research, the freezing and heating cycle is set to operate between -40 °C and 90 °C. Heat pipes used for testing in this research were 6 mm in diameter and 150 mm long with copper fiber spiral wick. Thermal performance tests were carried out on these heat pipes with charging ratio of working fluid varying between 10% to 30% by volume. It is observed that the thermal resistance of heat pipe with working fluid charging ratio in range of 10% to 25% by volume varies from 0.6 °C/W to 0.2 °C/W for the rate of heat transfer of 10 W-50 W. While the charging ratios beyond 25% have shown the higher thermal resistance in the range of 0.8 to 1.0 °C/W for similar rate of heat transfer. All the samples were subjected to 150 freezing and thaw cycles and did not show any signs of frost damage. Accelerated life tests were performed on these heat pipes for up to 500 h and did not presented any signs of degradation in their thermal performance. [ABSTRACT FROM AUTHOR]

This work presents a novel approach to achieve directional and normal thermal emission from epsilon‐near–zero (ENZ) materials. ENZ materials exhibit near–zero permittivity at the ENZ point, resulting in some unique properties compared to conventional optical materials including infinite wavelength, constant phase distribution, and decoupling of spatial and temporal fields inside the ENZ material. These properties are used to engineer the far‐field thermal emission from optical antennas fabricated on ENZ film in the mid‐infrared. By coupling the antenna resonance mode with the Berreman mode of the ENZ material, highly directional and normal emission is demonstrated. This approach could have significant implications for thermal management, energy conversion, and sensing applications. [ABSTRACT FROM AUTHOR]

In the present work, direct contact the refrigerant and the cells was employed for thermal management. This study experimentally investigates cooling the battery pack by allowing the refrigerant to directly contact the cells. Furthermore, it presents the first experimental evaluation of combining this approach with various active and passive cooling methods. According to the results, the cells' maximum temperature decreased by 34°C at the end of the discharge. In the proposed system, the heatsink served as the only heat transfer path to the environment, where. heat transfer occurred via free convection. To enhance heat dissipation from the heatsink, the system was combined with active or passive Battery Thermal Management Systems (BTMSs). Using hydrogel between the fins of the heatsink decreased the cells' maximum temperature by 0.5°C. However, the use of forced airflow between the fins of the heatsink did not affect the cells' maximum temperature. The proposed system was also combined with an active forced liquid cooling system, and various water flow rates were investigated. At a flow rate of 200 LPH, the cells' maximum temperature was reduced by 1.5°C compared to the mode without forced water flow. Additionally, different inlet water temperatures were examined, revealing that increasing the inlet water temperature leads to a significant rise in the cells' maximum temperature. [ABSTRACT FROM AUTHOR]

The design of an efficient thermal management system for a lithium-ion battery pack hinges on a deep understanding of the cells' thermal behavior. This understanding can be gained through theoretical or experimental methods. While the theoretical study of the cells using electrochemical and numerical methods requires expensive computing facilities and time, the Equivalent Circuit Model (ECM) offers a more direct approach. However, upfront experimental cell characterization is needed to determine the ECM parameters. In this study, the behavior of a cell is characterized experimentally, and the results are used to build a second-order equivalent electrical circuit model of the cell. This model is then integrated with the cooling system of the battery pack for effective thermal management. The Equivalent Circuit Model estimates the internal heat generation inside the cell using instantaneous load current, terminal voltage, and temperature data. By extrapolating the heat generation data of a single cell, we can determine the heat generation of the cells in the pack. With the implementation of the ECM in the cooling system, the coolant flow rate can be adjusted to ensure the attainment of a safe operating cell temperature. Our study confirms that 14% of pumping power can be reduced when compared to the conventional constant flow rate cooling system, while still maintaining the temperature of the cells within safe limits. [ABSTRACT FROM AUTHOR]

As the CMOS technology continuously scales down into the deep submicron regime and approaches the physical limits of minimization, Moore's Law is hindered. The proposed 3-D integrated circuit technology based on through silicon via brings hope. Although 3-D integrated circuits bring many advantages over 2-D integrated circuits, the thermal management challenges still need to be addressed effectively. The through silicon via carry signals while facilitating the thermal transfer of stacked chips due to their high thermal conductivity and offer a potential thermal management solution for 3-D integrated circuits. The through silicon via are structured in arrays to significantly improve heat dissipation. This paper proposes a cellular array structure that offers better heat dissipation capabilities compared to conventional rectangular arrays. First, the through silicon via cellular arrangement is described. Secondly, a method for modelling the equivalent thermal conductivity of through silicon via arrays is proposed. Finally, the excellent performance of the cellular structure on thermal conductivity is verified by a comparative analysis of the thermal characteristics of the through silicon via array in the COMSOL system using finite element method. The results presented in this paper are beneficial for designers to optimize the through silicon via array arrangement and predict the thermal performance of through silicon via arrays. In addition, it provides a reference for 3-D integrated circuit reliability design. [ABSTRACT FROM AUTHOR]

Purpose: Transient response of continuous composite material (CCM) fin made of high thermally conductive composite material is presented. The continuously varying effective properties of composite material such as thermal conductivity, heat capacity and density have been modelled using the Mori-Tanaka homogenization theory and rule of mixture. Additionally, temperature dependency of thermal conductivity, heat generation (composite materials) and convection coefficient (fluid properties) have also been incorporated. Different base boundary conditions are addressed such as oscillating heat flow, oscillating temperature, step-changing heat flow and step-changing temperature. At the other boundary, the fin is assumed to have a convective tip. Design/methodology/approach: Lattice Boltzmann method is implemented using an in-house source code for obtaining the numerical solution of typical non-linear heat balance equation of the aforementioned problem under various transient base boundary conditions. Findings: The effects of various thermal parameters such as material diffusivity ratio and conductivity ratio, area ratio and Biot number on transient response of fin and temperature distribution of fins are studied and interpreted. The heat transfer rate and time for attainment of steady state temperature of metal matrix composite (MMC) fin are found to be proportionally dependent on their diffusivity ratio. Additionally for higher values of area ratio and biot number, MMC fins are reported to dissipate the heat more efficiently in comparision to homogeneous fins in terms of time required to attain the steady state and surface temperature. Practical implications: Response of transient fin associated with advanced class of material can facilitates the practicing engineers for designing high-performance and/or miniaturized thermal management devices as used in electronic packaging industries. Originality/value: Studies of composite fin consisting of laminating second layer of material over the first layer have been reported previously, however transient response of CCM fin fabricated by continuously varying the volume fraction of two materials along the fin length has not been reported till date. Such material finds its application in thermal management and electronic packaging industries. Results are plotted in form of a graph for different application-wise material combinations that have not been reported earlier, and it can be treated as design data. [ABSTRACT FROM AUTHOR]

Diamond/aluminium composites have attracted attention in the field of thermal management of electronic packaging for their excellent properties. In order to solve the interfacial problem between diamond and aluminium, a novel process combining pressure infiltration with vacuum-assisted technology was proposed to prepare diamond/aluminum composites. The effect of diamond particle size on the microstructure and properties of the diamond/Al-12Si composites was investigated. The results show that the diamond/Al-12Si composites exhibit high relative density and a uniform microstructure. Both thermal conductivity and coefficient of thermal expansion increase with increasing particle size, while the bending strength exhibits the opposite trend. When the average diamond particle size increases from 45 µm to 425 µm, the thermal conductivity of the composites increases from 455 W·m-1·K-1 to 713 W·m-1·K-1 and the coefficient of thermal expansion increases from 4.97×10-6 K-1 to 6.72×10-6 K-1, while the bending strength decreases from 353 MPa to 246 MPa. This research demonstrates that high-quality composites can be prepared by the vacuum-assisted pressure infiltration process and the thermal conductivity of the composites can be effectively improved by increasing the diamond particle size. [ABSTRACT FROM AUTHOR]

Lithium-ion batteries still remain a cornerstone for the sustainable transportation by the way of its usage in electric vehicles (EVs). However, their optimal performance hinges on maintaining at consistent thermal conditions especially during operation, and at high discharge rates. The present study proposes a novel mini-channel cooling system specifically designed for a 10 Ah lithium-ion pouch cell. This innovative design incorporates cold plates on both battery surfaces for enhanced heat dissipation. In addition, the efficacy of silver (Ag) and copper oxide (CuO) nanofluid coolants by comparing with traditional water cooling in three distinct battery design configurations was also studied. Design 1 and 2 comprises respectively with partially and fully encased cold plates with mini-channels distributed both segmentally and centrally, and Design 3 the present proposed model featuring a fully covered cold plate with a serpentine flow layout for optimized heat transfer efficiency. Extensive computational analysis using ANSYS FLUENT 18.1 software reveals the superiority of Design 3. Notably, this configuration achieved significantly a lower maximum cell temperature (306.7 K and 305.0 K) with 0.25% and 0.5% Ag nanofluid coolants compared to Design 1 and 2, at a discharge rate of 5C. This underscores the potential of silver nanofluids for superior battery thermal management, particularly within the optimized Design 3 framework. These findings offer valuable insights for developing enhanced battery thermal management systems in EVs. [ABSTRACT FROM AUTHOR]

High-performance thermally conductive composites are increasingly vital due to the accelerated advancements in communication and electronics, driving the demand for efficient thermal management in electronic packaging, light-emitting diodes (LEDs), and energy storage applications. Controlling the orderly arrangement of fillers within a polymer matrix is acknowledged as an essential strategy for developing thermal conductive composites. In this study, isotactic polypropylene/GNP (iPP/GNP) composite filament tailored for fused deposition modeling (FDM) was achieved by combining ball milling with melt extrusion processing. The rheological properties of the composites were thoroughly studied. The shear field and pressure field distributions during the FDM extrusion process were simulated and examined using Polyflow, focusing on the influence of the 3D printing processing flow field on the orientation of GNP within the iPP matrix. Exploiting the unique capabilities of FDM and through strategic printing path design, thermally conductive composites with GNPs oriented in the through-plane direction were 3D printed. At a GNP content of 5 wt%, the as-printed sample demonstrated a thermal conductivity of 0.64 W/m · K, which was 1.5 times the in-plane thermal conductivity for 0.42 W/m · K and triple pure iPP for 0.22 W/m · K. Effective medium theory (EMT) model fitting results indicated a significantly reduced interface thermal resistance in the through-plane direction compared to the in-plane direction. This work shed brilliant light on developing PP-based thermal conductive composites with arbitrarily-customized structures. [ABSTRACT FROM AUTHOR]

The power density of electronic components grows continuously, and the subsequent heat accumulation and temperature increase inevitably affect electronic equipment’s stability, reliability and service life. Therefore, achieving efficient cooling in limited space has become a key problem in updating electronic devices with high performance and high integration. Two-phase immersion is a novel cooling method. The computational fluid dynamics (CFD) method is used to investigate the cooling performance of two-phase immersion cooling on high-power electronics. The two-dimensional CFD model is utilized by the volume of fluid (VOF) method and Reynolds Stress Model. Lee’s model was employed to calculate the phase change rate. The heat transfer coefficient along the heated walls and the shear-lift force on bubbles are calculated. The simulation data are verified with the literature results. The cooling performance of different coolants has been studied. The results indicate that the boiling heat transfer coefficient can be enhanced by using a low boiling point coolant. The methanol is used as the cooling medium for further research. In addition, the mass flow rate and inlet temperature are investigated to assess the thermal performance of twophase immersion cooling. The average temperature of the high-power electronics is 80°C, and the temperature difference can be constrained to 8°C. Meanwhile, the convective heat transfer coefficient reaches 2740 W/(m2·°C) when the inlet temperature is 50°C, and the mass flow rate is 0.3 kg/s. In conclusion, the results demonstrated that two-phase immersion cooling has provided an effective method for the thermal management of high-power electronics. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Polytechnic is the property of Journal of Polytechnic and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Thermal management systems using phase change materials (PCMs) can improve heat absorption and increase safe operating times. However, limited research has explored combining multiple PCMs within a system. This study investigates the thermal performance of a two-dimensional heat sink with varied PCM configurations. Simulations tested RT-54, CaCl2.6H2O, anfigd n-Eicosane arranged in different ways at 5 W and 7.5 W. Key results show CaCl2.6H2O with n-Eicosane increased the time to reach 40°C by 186% compared to CaCl2.6H2O alone at 5 W. Pairing CaCl2.6H2O and RT-54 improved time to 40°C by 425%. Increased power amplified these effects. The density and latent heat fusion of PCMs were critical factors. This demonstrates combining certain PCMs extends safe operating times more than using a single material. These optimal configurations can guide thermal management system design for electronics and other applications. [ABSTRACT FROM AUTHOR]

As a typical organic phase change material, paraffin occupies the large phase‐transition latent heat, promising electronic insulation, excellent cycling and chemical stability as well as the low corrosivity, which is attractive in the thermal management. In the practical applications, the surface of paraffin should be protected by organic or inorganic layers to inhibit the leakage above the melting point. However, in the reported paraffin composites, the weak cycling stability and the low thermal conductivity restricts their applications. In this paper, the highly thermal conductive hexagonal boron nitride nanosheets (hBNNS) are used as the protective layer for wrapping the paraffin in a microemulsion method to form the hBN‐paraffin thermal management composite, which exhibits the large phase‐transition latent heat ~189 J g−1, the excellent cycling stability over 20 cycles and the high thermal conductivity ~1.2 W m−1 K−1. The developed paraffin@ hBN composite should be promising for the thermal management in electronic packing, and can be used to improve the reliability of electric devices. [ABSTRACT FROM AUTHOR]

Battery Energy Storage Systems (BESS) are potential options for mitigating the effect of new loads and renewable energy storage systems. It's critical to have a strong battery thermal management system (BTMS) in place to keep the battery packs' characteristics and lifespan intact. The status of a battery is also an essential aspect to consider when it comes to performance. As a consequence, in this study, a fuzzy logic controller is utilized to enhance thermal management and the state of charge of a battery system. The usage of a hybrid cooling system that includes a phase change material (PCM) and a liquid cooling system, as well as Nano silver graphene particles, was first used to achieve thermal control. The coolant system is stimulated based on the controller's optimal temperature setting, allowing for efficient heat dissipation. Then implementing a feedback-controlled charging system that utilizes sequenced charging of the weak capacity battery in the pack to ensure maximum State of Charge (SOC) in the system improves the battery's SOC. Thereby the performance of the system showed enhanced results by maintaining the system at an optimum working temperature range not exceeding 40 °C. The system also achieved a battery voltage of 25.7 V and a battery current value of 5A after loading. The discharging voltage of the system is predicted to be 50.0275 V and the energy of the battery is found as 100 J after loading. As a result, the thermal management and the state of charge of the battery were improved by the incorporation of the fuzzy logic controller in the system. [ABSTRACT FROM AUTHOR]

Heat pumps have become a potential technology for future thermal management systems in space. However, conventional heat pumps lubricated with oil are currently unfeasible due to the difficulty separating oil in microgravity environments. The oil-refrigerant mixture reduces the heat transfer capacity of heat exchangers, and insufficient separation can damage the compressor. This paper proposes a new heat pump with gas bearings (HPGB) that combines a centrifugal compressor with externally pressurized gas bearings to solve lubrication problems. A numerical model is established to compare performance of the HPGB system with different refrigerants. The results show that the coefficient of performance (COP) of the HPGB system is slightly smaller than those of conventional heat pumps, but higher than those of heat pumps with the impact of an oil concentration of 5%, when evaporator power is 30 kW. The HPGB system is more suitable for high-power conditions because of the higher COP. Ammonia is the best choice for the HPGB system under high-power conditions (above 80 kW). R134a is the best choice under middle-power conditions (from 25 kW up to 80 kW). R1234yf is more suitable with the maximum COP of 2.88 under low-power conditions (below 25 kW). [ABSTRACT FROM AUTHOR]

Trench-fin MOSFETs, with their near-surface heat generation and the higher-surface area afforded by their geometry for thermal management, represent a promising solution to the thermal problems frequently encountered in lateral β-Ga2O3 devices. Here, we investigate potential thermal-management strategies for a vertical β-Ga2O3 trench-fin MOSFET through parametric analysis, offering recommendations on how best to design a device for maximal current density and excellent thermal performance. Primarily, by using a thermally conductive dielectric over the MOSFET structure, significant improvements to device power density may be achieved, aided by thermal spreading. Additionally, we find that by bonding thermal spreaders to its topside can yield significant improvements in thermal performance. [ABSTRACT FROM AUTHOR]

The transition from fossil fuel vehicles to electric has increased rapidly in recent years to reduce carbon emissions and use accessible energy. The main obstacles to the widespread use of electric vehicles are limited battery capacities, long charging times, thermal management in sudden charge and discharge situations and thermal runaway risks. The adverse effects of non-homogeneous temperature distribution on electrically driven vehicles have demonstrated the necessity of a thermal management system. The most used thermal management systems in practice are air-cooled, cooling plate (pipe) systems and direct dielectric cooling systems, which have recently become widespread. This study focused on the thermal analyses of the different thermal cooling methods. All analyses have been conducted using Ansys Fluent software. It has been observed that the dielectric direct cooling method, which is the newest method, has a performance value of 12% better than other systems at 1C normal operating conditions. [ABSTRACT FROM AUTHOR]

Aiming at the problem of high battery heat generation during the super fast-charging process of electric vehicle fast-charging power batteries, this study designs a fast-charging battery thermal management system based on the refrigerant direct cooling architecture. In order to use the refrigerant of refrigerant to cool the battery quickly. Firstly, the study constructs the heat generation model of the power battery, the calculation model of the battery thermal management system, and builds the experimental device. Secondly, theoretical simulations and experimental studies were conducted for low-temperature fast-charging and high-temperature fast-charging operating conditions. The experimental results show that the designed battery thermal management system has good cooling effect and temperature uniformity. [ABSTRACT FROM AUTHOR]

Conductive assembly film adhesives are extensively employed in medical, telecom, aerospace, and defense systems. Glass fabric cloth is frequently utilized as the carrier in many film adhesives to enhance handling and processability during electronic device assembly. Furthermore, practical applications have shown that film adhesives with glass fabric carriers can bond adherends with severely mismatched coefficients of thermal expansion. However, the impact of embedding glass fabric on the overall performance of assembly films has not been systematically investigated. To address this gap in knowledge, a study was conducted to compare the performance of electrically conductive film adhesives with and without the glass fabric carriers. The study focused on the mechanical performance of the film adhesives, including lap shear strength, tensile modulus, and the ability to manage applications with mismatched coefficients of thermal expansion. Additionally, the study assessed the impact of the carrier on the electrical and thermal conductivity of the film adhesives. Overall, this integrated assessment provides insights into the effectiveness of the glass fabric carrier on the performance of film adhesives. [ABSTRACT FROM AUTHOR]

Aerospace and defense applications present unique challenges for material suppliers. As increasing adoption of advanced semiconductor materials and Diverse Accessible Heterogeneous Integration technologies, power density of defense and aerospace devices increases rapidly. Traditional die-attaching technology is becoming an increasingly limiting factor in microelectronics packaging for the next generation aerospace and defense systems. Metal particle sintering creates a porous metal foam, which can significantly enhance heat transfer within the sintered material. However, the traditional silver sintering requires very high sintering temperatures that cannot be tolerated by typical microelectronics devices. In addition, the sintered metal foam contains open-cell pores that can absorb/entrap moisture and dusts, which poses a reliability risk. This article introduces an advanced hybrid silver sintering material, which incorporates highperformance silver sintering with high reliability and process-friendly of epoxy-based die-attaching technology. This hybrid sintering paste can be processed without applying any pressures in temperature ranges that are normal in microelectronics packaging processes. Preliminary experimental studies, including Scanning Electron Microscopic study, volume resistivity tests, die shear strength tests, and thermal resistance tests, were performed for developing a low temperature sintering schedule that is compatible with normal assembly processes of high-power density electronics devices. The results indicated that the hybrid material could achieve silver sintering at 150°C and offer 36 enhancement on thermal performance comparing with a widely used die-attach material. [ABSTRACT FROM AUTHOR]

Copyright of Gazi Üniversitesi Fen Bilimleri Dergisi Part C: Tasarım ve Teknoloji is the property of Gazi University and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The dielectric loss of Cu with high thermal conductivity is large at high frequency, which cannot meet the performance requirements in high-integrated circuits. There is an urgent need for materials to reduce its dielectric loss. In this paper, the thermal conductivity and dielectric properties of the AlN coating-Cu substrate system were controlled by changing the N2 pressure. The results showed that the crystallinity of hcp-AlN in AlN coating increased significantly when the proportion of N2 pressure was increased. With the increase of the N2 pressure, the particle size on the surface and the roughness of the coating improved. The AlN coating prepared at high N2 pressure had high dielectric constant and low dielectric loss at high frequency compared to those of the coatings prepared at low N2 pressure. At the same time, the AlN coating prepared under high N2 pressure on the Cu substrate did not decrease the thermal conductivity of Cu substrate. The AlN-Cu system prepared in this paper had high thermal conductivity and good dielectric properties, providing theoretical guidance for integrated circuit packaging and capacitor applications. [ABSTRACT FROM AUTHOR]

The cooling system is the auxiliary equipment that consumes the most energy in a data center, accounting for about 30 to 50% of the total energy consumption. In order to effectively reduce the energy consumption of a data center, it is very important to improve the heat exchange efficiency at the chip level. Compared with air cooling, single-phase cold plate liquid cooling, and immersion liquid cooling, the flat loop heat pipe (FLHP) is considered to be a better chip-level cooling solution for data centers. It has extremely high heat transfer efficiency and heat flux variability, and it can avoid the operation risk caused by liquid entering the server. In this paper, a FLHP with an evaporator designed with a "Tesla valve" flow channel configuration is developed. Experiments on the FLHP are carried out, focusing on the installation angles and cooling condition factors. The results show that an inclination angle of 20° is the critical point of the influence of gravity on the performance of the FLHP; to ensure good operation of the FLHP, the installation angle should be greater than 20°. The equivalent heat transfer coefficients of the FLHP condenser under different cooling conditions are calculated. It is found that water cooling can provide higher cooling heat transfer coefficients with lower energy consumption and operating noise. Additionally, the heat transfer limit, operating temperature uniformity, and start-up stability of the FLHP are significantly improved under water cooling conditions. The maximum heat load of the FLHP is up to 230 W, and the temperature difference of the evaporator surface can be controlled within 0.5 °C, under 20 °C water cooling. Finally, using the FLHP for thermal management of the chip, its heat transfer efficiency is 166 and 41% higher than that of air cooling and water cooling, respectively. [ABSTRACT FROM AUTHOR]

Air conditioning has become a necessity in people's daily life. The performance of the compressor determines the energy efficiency ratio of this electrical equipment, but the heat generated during the operation of its internal core power components will greatly limit its performance release, so it is urgent to carry out research on the heat dissipation of power devices. In this work, we explore the application of thermoelectric coolers (TECs) in the field of power device heat dissipation through finite element simulation. First, we geometrically modeled the structure and typical operating conditions of core power devices in air conditioners. We compared the temperature fields in air-cooling and TEC active cooling modes for high-power-consumption power devices in a 319 K operating environment. The simulation results show that in the single air-cooling mode, the maximum temperature of the 173.8 W power device reached 394.4 K, and the average temperature reached 373.9 K, which exceeds its rated operating temperature of 368.1 K. However, the maximum and average temperature of the power device dropped to 331.8 K and 326.5 K, respectively, at an operating current of 7.5 A after adding TECs, which indicates that TEC active cooling has a significant effect on the temperature control of the power device. Furthermore, we studied the effect of the TEC working current on the temperature control effect of power devices to better understand the reliability of the TECs. The results show that TECs have a minimum working current of 5 A, which means it has no significant cooling effect when the working current is less than 5 A, and when increasing the current to 10 A, the average temperature of the power device can be reduced to 292.9 K. This study provides a meaningful exploration of the application of TECs in chip temperature control and heat dissipation, providing a new solution for chip thermal management and accurate temperature control. [ABSTRACT FROM AUTHOR]

Thermal conductive materials with low dielectric constant under high frequencies play an important role in high-power integrated circuits packaging. The application of Cu in the packaging substrates is limited due to the high dielectric constant. In this paper, the AlN coatings were deposited on the Cu substrates to maintain the high thermal conductivity and obtain excellent electrical properties for the first time. The microstructure, thermal conductivity and electrical properties of the AlN/Cu systems were adjusted by duty cycles. The results show that improving the duty cycle reduced the hcp-AlN (002) preferred orientation degree of the coatings. The growth structure of the coatings could be regulated by increasing the duty cycle, which induced the grain and particle size first increasing and then decreasing. AlN/Cu systems improved the thermal conductivity of Cu. All coatings show far higher resistivity than Cu and 0.006–0.24 low dielectric loss. The minimum dielectric constant (5.6) of the coating at 2000 kHz frequency was obtained. The AlN/Cu systems in this paper realize high thermal conductivity and excellently dielectric properties, meeting the application in high-power integrated circuit packaging. [ABSTRACT FROM AUTHOR]

The operating temperature of a battery energy storage system (BESS) has a significant impact on battery performance, such as safety, state of charge (SOC), and cycle life. For weather-resistant aluminum batteries (AlBs), the precision of the SOC is sensitive to temperature variation, and errors in the SOC of AlBs may occur. In this study, a combination of the experimental charge/discharge data and a 3D anisotropic homogeneous (Ani-hom) transient heat transfer simulation is performed to understand the thermal effect of a novel battery system, say an aluminum-ion battery. The study conducts a turbulence fluid dynamics method to solve the temperature distribution of the battery rack, and the entropy generation method analyzes the heat generation of AlB during the charging/discharging process. The AlB is modeled by a second-order Thevenin equivalent circuit to estimate the status of the battery. An extended Kalman filter is applied to obtain the accurate SOC for monitoring the battery cell. The current study conducts the Galvanostatic Intermittent Titration Technique (GITT) on aluminum-ion batteries under different operation temperatures: 25 °C, 40 °C, 60 °C, and 80 °C. According to the sensitivity analysis of the SOC, the temperature sensitivity tends to or greater than one, S T ≥ 1 , while the operation temperature is above 40 °C, and the SOC modification of EKFtmep estimator improves the battery state of charge in the error range below 1%. [ABSTRACT FROM AUTHOR]

Aiming at the thermal safety and inconsistency caused by the high temperature of lithium‐ion (Li‐ion) battery, a cooling structure embedded with a flat aluminum heat pipe (FAHP) for a Li‐ion battery module is proposed. The three‐dimensional thermal model of the FAHP module is established by considering regionalized thermal radiation. The thermal characteristics of the module are compared with four progressive cooling schemes, and the temperature performance affected by different convection (hconv) and radiation (hrad) heat transfer coefficients are analyzed. Results show that, the thermal model with the thermal radiation is more precise than that without the thermal radiation under the natural convection. Adding FAHPs can effectively reduce the maximum temperature (Tmax) and the maximum temperature difference (ΔTmax,pack) of the FAHP module. Especially adding FAHPs with fins, even at 3C discharging, the average cooling performance can be improved by 33.3%, 25.0%, and 14.4% than that of natural convection, aluminum plates sandwiched between cells and FAHPs with no fins, respectively. Meanwhile, the decrease in rates of Tmax and ΔTmax,pack are gradually increasing with the increasing of hrad, but decreased with the increasing of hconv. When 5 W·m−2·K−1 ≤ hconv ≤ 35 W·m−2·K−1, the average ratio of radiation heat dissipation to total heat dissipation (η) is 35.7%, but when hconv > 55 W·m−2·K−1, η is less than 1.5%. [ABSTRACT FROM AUTHOR]

The dynamic response characteristic is an important performance indicator of the proton exchange membrane fuel cell (PEMFC), which has a great influence on the durability and reliability. The cooling capacity is an important factor that affects the stability of the PEMFC output after the change. This research proposes to apply the micro-heat pipe array (MHPA) to the thermal management of PEMFC. A novel MHPA-PEMFC stack is designed, and four cases involving comparative dynamic response experiments are studied. The results show that compared with the traditional air-cooled PEMFC, the MHPA-PEMFC significantly reduces the maximum step voltage, dynamic internal resistance and step temperature, shortens the temperature response time and improves the internal temperature uniformity. In the case where the output current stepped up from 10 to 30 A, the maximum step voltage and the maximum dynamic impedance of MHPA-PEMFC are lower than those of PEMFC by 0.449 V and 0.037 Ω, respectively. The maximum step temperature has been reduced by 4.44 °C, and the temperature response time has been reduced by 180 s. The research results provide a basis for using MHPA in PEMFC thermal management applications. [ABSTRACT FROM AUTHOR]

Quad Small Form-factor Pluggable-Double Density (QSFP-DD) is the smallest high-speed (>14 Tb/s) interconnect system and is widely used in cloud computing and 5G network. However, the high-speed feature comes at the cost of large power dissipation. The QSFP-DD system contributes 400 to 960 W per rack unit, which necessitates its thermal management. The authors, having identified a knowledge gap in the existing literature, humbly hope to pioneer a thermal-hydraulic study for QSFP-DD. The study starts with experiments in a wind tunnel wherein temperature, power, fan speed, and pressure are measured. The experimental data are used to validate computational fluid dynamics (CFD) models. Both lumped fan and multiple reference frame fan models have been studied with comparisons versus experimental data. Subsequently, the focus of CFD study is shifted to the QSFP-DD system's thermal-hydraulic structures, including variation in fins' height, quantity, and the grille free area ratio. Finally, the CFD results are processed into an empirical Nusselt number correlation for thermal performance prediction. The study reveals that optimum thermal performance could be achieved by balancing heat sink fin area and pressure drop of the system. [ABSTRACT FROM AUTHOR]

Metal hydrides are a class of materials that can absorb and release large amounts of hydrogen. They have a wide range of potential applications, including their use as a hydrogen storage medium for fuel cells or as a hydrogen release agent for chemical processing. While being a technology that can supersede existing energy storage systems in manifold ways, the use of metal hydrides also faces some challenges that currently hinder their widespread applicability. As the effectiveness of heat transfer across metal hydride systems can have a major impact on their overall efficiency, an affluent description of more efficient heat transfer systems is needed. The literature on the subject has proposed various methods that have been used to improve heat transfer in metal hydride systems over the years, such as optimization of the shape of the reactor vessel, the use of heat exchangers, phase change materials (PCM), nano oxide additives, adding cooling tubes and water jackets, and adding high thermal conductivity additives. This review article provides a comprehensive overview of the latest, state-of-the-art techniques in metal hydride reactor design and heat transfer enhancement methodologies and identifies key areas for future researchers to target. A comprehensive analysis of thermal management techniques is documented, including performance comparisons among various approaches and guidance on selecting appropriate thermal management techniques. For the comparisons, the hydrogen adsorption time relative to the reactor size and to the amount of hydrogen absorbed is studied. This review wishes to examine the various methods that have been used to improve heat transfer in metal hydride systems and thus aims to provide researchers and engineers working in the field of hydrogen storage with valuable insights and a roadmap to guide them to further explore the development of effective thermal management techniques for metal hydrides. [ABSTRACT FROM AUTHOR]

PV-based mini-grids are identified as a feasible and, often, only economically viable option for the electrification of Kenyan remote and scattered rural areas, where connection to the national grid is challenging, and the related costs are high, if not prohibitive. This paper presents the analysis of typical Kenyan PV mini-grids by using some results of the work in the project "Reliable, Efficient and Sustainable Mini-Grids for Rural Infrastructure Development in Kenya (RESILIENT)". After presenting average annual and seasonal daily load profiles of residential and small commercial mini-grid customers identified from the measured demands, the paper introduces the main mini-grid components and their models, including a simplified, but reasonably accurate, model of a mini-grid battery storage system based on the manufacturer's charge–discharge curves. All mini-grid components are assembled in a scalable and easily reconfigurable simulation model of an actual Kenyan PV mini-grid, and they are implemented for the evaluation of PV mini-grid performance and the potential for expansion and connection of additional residential and small commercial customers. During the validation of the developed simulation model using available measurement data, an empirical approach for adjusting the PV system output power is specified for a more accurate match with the measurements. The presented results indicate the importance of the information on the actual control algorithms and control settings of the mini-grid energy management systems, on the thermal dependencies and characteristics of both PV generation system and battery storage system, and on the availability of on-site measurements of temperature and input solar irradiance. The developed PV mini-grid model can be used for further analyses, such as to study the techno-economic performance of different mini-grid configurations, to identify the optimal sizing of mini-grid components, and to specify efficient control and operation schemes based on the locally available resources. [ABSTRACT FROM AUTHOR]

Copyright of Chinese Journal of Refrigeration Technology is the property of Shanghai Society of Refrigeration and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Chinese Journal of Refrigeration Technology is the property of Shanghai Society of Refrigeration and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Chinese Journal of Refrigeration Technology is the property of Shanghai Society of Refrigeration and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The thermal boundary conductance (TBC) of metal/dielectric couples was measured for a large variety of metals on silicon, sapphire, and diamond using time domain thermoreflectance and compared to data previously obtained on diamond. In the case of silicon, HF-cleaned and RF-etched surfaces were tested. The detailed structure of these interfaces was studied, allowing distinction of two different cases of M/Si couples: (i) some amount of interfacial reaction exists for both surface terminations, resulting in similar TBCs; and (ii) chemically abrupt interfaces are achieved, resulting in TBC values that are always lower for RF-etched samples. The TBC values obtained on different substrates allowed identifying a tendency of the TBC to scale with the maximum transmission limit. A possible influence of the substrate was evaluated using both the diffuse mismatch model (DMM), which predicts a strong dependence on the substrate properties, and a newly developed approach based on the metal irradiance (IM), which predicts no dependence on the substrate properties. The DMM was implemented using a Debye model with either a linear (DMMLinear) or a Sine-Type (DMMSineType) dispersion, while the IM was implemented using a Sine-Type (IMSineType) dispersion. The DMMLinear and the IMSineType were found to be more suitable than the DMMSineType and to be equally precise in predicting TBC at metal/silicon and metal/sapphire interfaces. The IMSineType is found to be better suited than both the DMMLinear and the DMMSineType to predict TBC at metal/diamond interfaces. IMSineType being the only model tested that is suitable for all three substrates, it appears to be the most appropriate choice. As a corollary, we find that the TBC dependence on substrate properties is much weaker than predicted by the DMM. [ABSTRACT FROM AUTHOR]

Interfacial thermal resistance between metal and dielectric materials is a bottleneck of the thermal management for modern integrated circuits as interface density increases with thinner films. In this work, we have observed that the interfacial resistance across gold and aluminum oxide can be reduced from 4.8 × 10 − 8 m 2 K / W to 1.4 × 10 − 8 m 2 K / W after adding a nickel layer in between, which represents a 70% reduction. The two temperature model is applied to explain the reduction of interfacial resistance, and the results show that the nickel layer functions as a bridge that reduces the phonon mismatch between gold and aluminum oxide. Moreover, nickel has strong electron-phonon coupling, which reduces the thermal resistance caused by the weak electron-phonon coupling in gold. [ABSTRACT FROM AUTHOR]