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The relatively smaller die size of SiC chips makes the heat flux increase significantly, which brings new challenges to the thermal management and reliability of SiC power modules. This paper proposes a new thermal enhanced packaging method based on vapor chamber (VC) phase change heat spreader (PCHS) for SiC power modules, achieving the advantages of high thermal conductivity, low weight, low cost and low thermal stress. In this design, SiC MOSFET bare dies are directly soldered on the top of VC-PCHS, which not only act as heat spreaders but also conduct their drain current. The integrated VC-PCHS is optimized based on thermal and thermomechanical performances. A SiC power module prototype directly integrated with VC-PCHS is built using a new fabrication process. Both the simulations and experiments demonstrate significant improvements in thermal and thermomechanical performance. The modules integrated with VC-PCHS can operate under 200 W of power dissipation per die (632 W/cm2) without exceeding the maximum rated junction temperature. This paper reveals the potential of directly integrating phase change cooling components inside power modules, providing a new solution to improve the thermal performance and reliability of SiC power modules without adding complexity and energy consumptions to external cooling systems.

Thermal analysis is an essential step that enables co-design of the computing system (i.e., integrated circuits and computer architectures) with the cooling system (e.g., heat sink). Existing thermal simulation tools are limited by several major challenges that prevent them from providing fast solutions to large problem sizes that are necessary to conduct standard-cell level thermal analysis or to evaluate new technologies or large chips. To overcome these challenges, we introduce a SPICE-based PArallel Compact Thermal simulator (PACT) that achieves fast and accurate, standard-cell to architecture-level, steady-state and transient parallel thermal simulations. PACT utilizes the advantages of multicore processing (OpenMPI) and includes several solvers to speed up both steady-state and transient simulations. PACT can be easily extended to model a variety of emerging integration and cooling technologies by simply modifying the thermal netlist. In addition, PACT can also be used with popular architecture-level performance and power simulators. In comparison to a state-of-the-art finite-element method (FEM) based simulator (COMSOL), PACT has a maximum error of 2.77% and 3.28% for steady-state and transient thermal simulations, respectively. Compared to a popular compact thermal simulator, HotSpot, PACT demonstrates a speedup of up to 1.83× and 186× for steady-state and transient simulations, respectively. We also show the applicability and extensibility of PACT through modeling emerging integration and cooling technologies, such as monolithic 3D ICs and liquid cooling via microchannels, and full-system simulation integration on a 2.5D system with silicon-photonic network-on-chips (PNoCs).

A number of thermal management devices are used to actuate concentrated electronic appliances in an efficient way. A liquid cooling plate acts as a heat sink enclosed by materialized walls. This work aims to carry out design of liquid cooling plates such that the heat diffused by the electronic equipment is removed while their temperatures levels remain within safe limits. The liquid cooling plates expose “cold surfaces” to electronic appliances. The performance of a cooling plate is estimated depending upon heat carrying capacity, associated heat transfer rates and concentrated thermal regions on the plate surface. For this study, the design of liquid cooling plate was done with SOLIDWORKS. Pure water was used as a working fluid in test channels. A comparative analysis of flow distribution, temperature contours, pressure drop and pumping power for different channel configurations was carried out with ANSYS. It was observed that a channel configuration is of key importance in liquid cooling plates. The findings from this study are beneficial for the optimum design of cooling systems for high heat flux applications, i.e., in electronic devices, computer processors and automotive engines.

Thermal management of electrical machines is an important issue to improve electromagnetic performance, reduce system size and prolong lifetime. Based on the equivalent thermal circuit (ETC) and computational fluid dynamics (CFD) methods, the temperature rise characteristic of a high-speed stator-permanent magnet-type flux switching (HS-SPMFS) machine for fuel-cell electric vehicle compressor is predicted. Firstly, the structural features, key dimensions, material properties and heat generation rate of the HS-SPMFS machine and its cooling system are introduced. Secondly, the ETC model of the machine with a liquid cooling channel is proposed, and the size of the cooling system is preliminarily designed. The influence mechanism of the number, size and flow rate of the water channel on the convective heat transfer area, convective heat transfer coefficient, water head loss and winding temperature rise is revealed. On this basis, combined with the CFD method, the temperature distribution of the machine is studied, and the detailed temperature distributions of each component of the machine are obtained and verified by the ETC method considering the cooling system. Finally, a HS-SPMFS machine prototype is manufactured and the temperature test platform of the prototype is built. The temperature rise behaviors of the machine under different working conditions are tested, verifying the theoretical analysis and the prediction methods.

In the work, a composite cooling system coupled with PCM (phase change material) and liquid cooling was designed. The influence of parameters such as spacing, EG (expanded graphite) content, battery direction, coolant flow rate and pipe diameter on the cooling performance was analyzed. The results revealed that: (1) The increase of spacing makes the temperature of the pack decrease, but the effect degree of increasing the spacing on temperature performance decreases when the spacing exceeds 14 mm. At the same time, CPCM formed by the added high thermal conductivity material expanded graphite and paraffin can effectively improve the temperature control performance of the pack, which can control the temperature at 313.15K under the condition of an ambient temperature of 308.15K (2) By comparing the maximum temperature and the temperature difference of the pack under different discharge methods, it is concluded that the poles facing inward can reduce the accumulation of the interior heat. (3) The convective heat transfer coefficient and Nu number of the pack are increasing as the flow rate increases, but the slope of the temperature versus flow rate decreasing slowly. After increasing the inlet size, the inner wall surface area of the pipe increases and the average convective heat transfer coefficient of the pack reduces. However, the Nu number increases with the increase of the pipe diameter, indicating that the growth of the pipe diameter can enhance the heat transfer rate. (4) Orthogonal experiment and fuzzy correlation analysis were combined to analyze the parameters that affect the thermal performance of the BTMS. It was determined that using a proper coolant flow rate can maximize the thermal performance of the pack.

Herein, a horizontal CPU cooler with a pulsating heat pipe for cooling desktop computer was developed. In the experiment, an electric heating block was used to heat a copper plate to simulate the heating process of CPU. The cooling system consists of a cooling fan and a pulsating heat pipe cooler. The influence of cooling wind speed and heat load on heat transfer performance, start-up performance, and temperature uniformity of the pulsating heat pipe cooler was analyzed by controlling variable method. The wind speed was set to be 0 m/s, 0.1 m/s, 0.3 m/s, 0.5 m/s, and 0.7 m/s, respectively. The contour plots were used to analyze the uniformity of temperature distribution due to cooler. The results show that the start-up of the pulsating heat pipe led to a decrease in temperature of CPU. As the cooling wind speed increased, the start-up time of the pulsating heat pipe dropped, the start-up temperature dropped, and its stability was also improved. The operation at different cooling wind speeds also changed the start-up mode of the pulsating heat pipe. The start-up performance was best at cooling wind speed of 0.3 m/s. The contour plot for temperature showed that the temperature distribution of the pulsating heat pipe cooler became more uniform with increased cooling wind speeds. There was excellent temperature uniformity at the cooling wind speeds of 0.3 m/s and 0.7 m/s. When the cooling wind speed was 0.7 m/s, the minimum average thermal resistance was 0.51 K/W.

In order to investigated the influence on the liquid cooling system cooling effect by changing the structural parameters, single Li-ion battery heat generation model is conducted, and used in following simulation. Subsequently, sixteen models are designed by orthogonal array, and the results are obtained by extremum difference analysis, which can quantify the influence degree, identify major and minor factors, and find the relatively optimum combination. Finally, different channel entrance layout is adopted to investigated. With a series of work, the effective of single battery heat generation model is proved by the discharge experiment. The coolant velocity has most evident influence on the Li-ion battery temperature rise, rectangular channel aspect ratio is second one, and the heat conducting plate thickness has the smallest influence. Similarly, for Li-ion battery temperature difference, the effect of heat conducting plate thickness and rectangular channel aspect ratio as the same, both are secondary factor, and coolant velocity is main factor. With different channel entrance layout, both the maximum temperatures denote a same upward trend, and better balance temperature distribution is obtained by adopt Case C system which with alternating arrange channel entrance layout.

This study investigates the issues involved in the design of a compact two-phase thermosyphon in which the locations of evaporator and condenser need a high degree of freedom. Enhancement of boiling heat transfer in the compact evaporator space was achieved by a microfabricated structure. Anticipating situations where gravity does not provide sufficient potential to drive the condensate, a pump-assisted circulation loop was studied. The relative height between the evaporator and condenser and the pumping rate were systematically varied by utilizing two thermosyphon loops. Close examination of the data suggests that there could be an optimum point in the parametric domain where the thermal resistance is minimized with least assistance from the pump.

Gels are soft functional materials with solid networks and open pores filled with solvents (for wet gels) or air (for aerogels), displaying broad applications in tissue engineering, catalysis, environmental remediation, energy storage, etc. However, currently known gels feature only a single (either solid-liquid or solid-vapor) interface, largely limiting their application territories. Therefore, it is both fundamentally intriguing and practically significant to develop conceptually new gel materials that possess solid-liquid-vapor multiple interfaces. Herein, we demonstrate a unique solid-liquid-vapor triphase gel, named as aerohydrogel, by gelling of a poly(vinyl alcohol) aqueous solution with glutaraldehyde in the presence of superhydrophobic silica aerogel microparticles. Owing to its continuous solid, liquid, and vapor phases, the resultant aerohydrogel simultaneously displays solid-liquid, solid-vapor, and liquid-vapor interfaces, leading to excellent properties including tunable density (down to 0.43 g·cm-3), considerable hydrophobicity, and excellent elasticity (compressive ratio of up to 80%). As a proof-of-concept application, the aerohydrogel exhibits a higher evaporative cooling efficiency than its hydrogel counterpart and a better cooling capability than the commercial phase change cooling film, respectively, showing promising performance in cooling various devices. Moreover, the resulting aerohydrogel could be facilely tailored with specific (e.g., magnetic) properties for emerging applications such as solar steam generation. This work extends biphase gel (hydrogel or aerogel) to solid-liquid-vapor triphase gel, as well as provides a promising strategy for designing more aerohydrogels serving as soft functional materials for applications in various emerging fields.

Thermal management is considered a critical issue in proton exchange membrane fuel cells (PEMFCs), since it not only influences the cell performance but also impacts PEMFC’s reliability and durability. With the ever-increasing power density of PEMFC, traditional cooling approaches including air cooling and water cooling become difficult to meet the demand for high-power heat dissipation. Therefore, phase-change cooling is proposed for fuel cell application in this work, and the potential advantages are discussed and demonstrated via a mathematical model incorporating phase-change heat transfer. The thermal management performance is evaluated by temperature uniformity, maximum temperature difference, and the cooling capacity to compare the difference between phase-change cooling and traditional methods, which demonstrates that phase-change cooling owns a greatly improved thermal management performance. In addition, a simple method to broaden the operating temperature of phase-change cooling based on one certain coolant is offered, which is pressurizing in the coolant channel to regulate the boiling temperature that could further improve the application feasibility of phase-change cooling strategy in fuel cells.

To address the growing energy use of data centers, waste heat recuperation offers a solution to better integrate these facilities into the broader energy system, thus facilitating a transition to the decarbonization of the energy system. The use of liquid coolants for full immersion cooling or local heat extraction from high power density components is considered for this purpose. However, heat can also be extracted by novel air cooling approaches, perhaps in combination with localized liquid cooling. To optimize heat extraction from air-cooled systems and maximize the heat grade, synthetic jets (SJs) can be used for targeted adaptive cooling in conjunction with air ducting to facilitate maximum heat recuperation potential in rack or server-mounted air-to-liquid heat exchangers. Internal server layouts can be optimized numerically, e.g., using a multiple objective genetic algorithm approach based on minimization of entropy generation rates. However, since SJs are inherently transient flow phenomena, this would require transient flow simulations, which forms a bottleneck in a numerical optimization loop. This research aims to develop a simplified steady-state representation of a synthetic jet actuator (SJA) with slot orifice using a localized body force to generate a similar time-averaged flow field to a real SJA, suitable for steady Reynolds-averaged Navier–Stokes simulations within a numerical optimization loop. Both flow fields are compared in terms of the mean flow field, jet spreading rate, and turbulence intensity distributions.

This article presents an experimental investigation of two-phase passive liquid cooling, using a miniature-thermosyphon, for the simulated three-dimensional stacked integrated chips (3D-SICs). An evaporator consisting of three heaters separated with two micro-gaps of height 0.178 mm serves as a core component of the miniature-thermosyphon system. The thermosyphon’s cooling performance has been evaluated under multiple parametric conditions, including evaporator tilt angle, vertical separation between the condenser and the evaporator, and inlet-chilled water temperature of the condenser in the auxiliary loop. Boiling regimes at evaporator outlets are presented. All the investigated characteristics except the tilt angle have notable impacts on the cooling performance of each layer of the simulated 3D-SICs. Nonuniform cooling performance between the simulated 3D-SICs layers and within each layer has been observed. This nonuniform cooling performance could require the preferred placement of 3D-SICs with heterogeneous chips in data center cabinets.

Computing capacity has always been on the upward climb due to the constant technological improvements in semiconductor manufacturing and packaging industry. This growth in computing capability is usually accompanied by a steep rise in heat flux density associated with the electronic component (CPUs or GPUs, for example). High-performance computing (HPC) data centers often employ several of these high-performance devices for crunching their enormous artificial intelligence (AI) or scientific computing workloads. State-of-the-art air cooling technologies throttle after a certain heat flux level and would require bigger heat sinks driving enormous airflow through it, which may not be desirable from a data center operation standpoint. Hence, a lookout for advanced thermal management techniques is quite imperative. In this article, a commercially available intel overclockable CPU i9-9900k was exercised with high performance workloads while employing and evaluating three different cooling technologies namely air-cooled, cold plates, and two-phase (2P) immersion. The high heat carrying capacity associated with cold plates and 2P immersion techniques outperformed the air-cooled solution by constantly yielding higher CPU clock rates up to 41% utilizing cold plates and 51% employing 2P immersion. The performance of cold plates and 2P immersion was evaluated at different functional points (different coolant operating temperatures and 2P coolant types for example) to understand how the technologies would respond in a legacy or modern data center operation. It was again observed that both 2P immersion technology and cold plates provided the least thermal resistance (as low as 0.247 °C/W) path to heat transfer and therefore provided higher computational performance and efficiency compared to air cooling. Further improvement in performance is not limited by cooling but by packaging constraints. Advanced packaging techniques coupled with minimizing the interfacial resistance can reap enhanced performance and energy efficiency gains using these modes of cooling. This article demonstrates the potential increase in virtual machine (VM) performance that can be attained using cold plates or 2P immersion. Authors recommend adoption of liquid cooling in early chip design and architecture phases. Finally, the article provides a generic overclocking methodology that the industry can use to qualify postturbo server class chip performance.

A cooling technology roadmap is defined for power electronics modules such as insulated gate bipolar transistors (IGBT) and wideband gap semiconductor modules (SiC/GaN). These power modules are widely used for inverter and converter applications. Cooling technologies studied include natural air cooling, forced air cooling, forced liquid cooling, and thermal management technologies employing phase change. This work reviews the standard modes of failures of power electronics modules. The work helps to understand the thermal resistances at various interfaces in the module stack. The study highlights the importance of using electrothermal models for power loss estimation. Effective thermal management must ensure the power electronics components' junction (die) temperature is within the desired limits. The developed cooling technology roadmap suggests using heat flux at the module base and heat generation per temperature rise in the die as a metric for selecting cooling technology. Further, the review also stresses the importance of junction temperature swings experienced by the die during transient operation.

Efficient fast-charging technology is necessary for the extension of the driving range of electric vehicles. However, lithium-ion cells generate immense heat at high-current charging rates. In order to address this problem, an efficient fast charging–cooling scheduling method is urgently needed. In this study, a liquid cooling-based thermal management system equipped with mini-channels was designed for the fast-charging process of a lithium-ion battery module. A neural network-based regression model was proposed based on 81 sets of experimental data, which consisted of three sub-models and considered three outputs: maximum temperature, temperature standard deviation, and energy consumption. Each sub-model had a desirable testing accuracy (99.353%, 97.332%, and 98.381%) after training. The regression model was employed to predict all three outputs among a full dataset, which combined different charging current rates (0.5C, 1C, 1.5C, 2C, and 2.5C (1C = 5 A)) at three different charging stages, and a range of coolant rates (0.0006, 0.0012, and 0.0018 kg·s−1). An optimal charging–cooling schedule was selected from the predicted dataset and was validated by the experiments. The results indicated that the battery module’s state of charge value increased by 0.5 after 15 min, with an energy consumption lower than 0.02 J. The maximum temperature and temperature standard deviation could be controlled within 33.35 and 0.8 °C, respectively. The approach described herein can be used by the electric vehicles industry in real fast-charging conditions. Moreover, optimal fast charging–cooling schedule can be predicted based on the experimental data obtained, that in turn, can significantly improve the efficiency of the charging process design as well as control energy consumption during cooling.

In recent years, PCR-based methods as a rapid and high accurate technique in the industry and medical fields have been expanded rapidly. Where we are faced with the COVID-19 pandemic, the necessity of a rapid diagnosis has felt more than ever. In the current interdisciplinary study, we have proposed, developed, and characterized a state-of-the-art liquid cooling design to accelerate the PCR procedure. A numerical simulation approach is utilized to evaluate 15 different cross-sections of the microchannel heat sink and select the best shape to achieve this goal. Also, crucial heat sink parameters are characterized, e.g., heat transfer coefficient, pressure drop, performance evaluation criteria, and fluid flow. The achieved result showed that the circular cross-section is the most efficient shape for the microchannel heat sink, which has a maximum heat transfer enhancement of 25% compared to the square shape at the Reynolds number of 1150. In the next phase of the study, the circular cross-section microchannel is located below the PCR device to evaluate the cooling rate of the PCR. Also, the results demonstrate that it takes 16.5 s to cool saliva samples in the PCR well, which saves up to 157.5 s for the whole amplification procedure compared to the conventional air fans. Another advantage of using the microchannel heat sink is that it takes up a little space compared to other common cooling methods.

Fast and accurate thermal analysis is critical in designing power electronics converters through virtual prototyping to achieve high power density, efficiency, etc. Virtual prototyping can save cost and time in comparison to hardware prototyping and experimental test and can lead to an overall optimized design. For removing the heat in power converters effectively, forced convection, such as air cooling or liquid cooling, is usually adopted. To estimate the temperature distribution and assist the layout optimization without building physical prototypes, fast and accurate thermal prediction is required, which is an essential area in virtual prototyping of power electronics. In this article, a thermal-flow network (TFN) modeling method is proposed to solve the flow and temperature distribution in a power converter. The flow distribution is calculated by flow network consisting of flow resistances, flow branches, and sources. The temperature distribution is then estimated by the thermal network, where the related boundary conditions (heat transfer coefficient and local fluid temperature) are assigned using empirical equations. The fundamental and basic circuit elements for the TFN modeling method have been implemented in software, which helps to build the TFN modularly. The comparison between the proposed method, computational fluid dynamics (CFD), and experiment is provided to show the effectiveness of the TFN modeling method. The proposed modeling and analysis process can also be adapted for other forced cooling methods.

High performance cooling anticipated in smaller size heat transfer equipment is the most significant challenge in many industries including CPU cooling, refinery, petrochemical, power stations, automobiles, etc. Nanoliquids are a new class of thermal fluids for better heat transfer rate and least energy consumption. In this work, cupric oxide/silica hybrid nanoliquids are synthesized using water as base fluid. The synthesized nanofluids are characterized using X-Ray Diffraction, Transmission Electron Microscopy, Selected Area Electron Diffraction and Scanning Electron Microscopy—Energy-Dispersive X-ray Spectroscopy analysis to confirm their crystal structure, size, shape and elemental constituents. The stability was analyzed using Zeta potential instrument and their thermophysical properties were measured for various temperatures and concentrations. The hybrid nanoliquids are circulated into the jacketed vessel to extract the heat from the fluid inside the vessel. Using the measured properties and the temperatures of fluid inside the vessel and jacket side, overall heat transfer coefficient was calculated for the nanofluid and conventional coolant and the results are compared. Results indicate that heat transfer is directly proportional to flow rate and volume concentration and it was found that 48.6% enhancement in overall heat transfer coefficient was achieved for 3 LPM flow rate at 0.2% concentration.

In order to solve the problem of excessive temperature rise caused by 2.5 WM permanent magnet wind turbine in operation, this paper designs a heat dissipation system. The combination structure of the heat exchanger and the heat sink was determined, as well as the heat dissipation method of the internal and external cycle isolation heat exchange. The control method and operation mode with Siemens PLC as the core are put forward. The computational fluid dynamics method is utilized to design the air-cooling heat exchanger and the liquid-cooled heat sink of the heat dissipation system. The results show that the cooling pipe gap has a great impact on the liquid cooling effect. The cooling pipe arrangement and piping arrangement of the air-cooled heat exchanger and liquid-cooled radiator are optimized. Finally, taking a 2.5 MW direct-drive permanent magnet wind turbine as an example, four environmental temperatures were selected to test generators in rated power. Verify that the cooling system is designed to meet cooling requirements.

In electric vehicles and hybrid electric vehicles, insulated-gate bipolar transistor (IGBT) power module trends to dissipate higher heat flux due to increased power rating and reduced package size. An inefficient cooling method will result in stringent thermal reliability problems. Therefore, there is a strong need for innovative and efficient cooling technologies in order to tackle these issues. In this article, a localized direct phase-change cooling strategy is applied and integrated with direct bonded copper in IGBT power module. Vapor chamber with light weight, high thermal conductivity, and even temperature uniformity replaces original copper baseplate. Layers of thermal grease and original cooling plate are removed, leading to a further reduction in thermal resistance. In order to evaluate the new module, a thermal model and an experiment were built to analyze temperature distribution in layers, junction temperature, temperature uniformity, and thermal resistance. Results indicate the integrated thermal management system outperforms traditional cooling solutions on the cooling capacity. Improvements on junction temperature, temperature uniformity, and total thermal resistance are 34.6%, 76.6%, and 41.6%, respectively. The results illustrate the potential of phase-change cooling by vapor chamber. It provides a new perspective in the compact and efficient design of power electric modules.

Tooth coil windings, in particular when using a double layer structure, present opportunities for in-slot liquid cooling. Since the windings are not overlapping, access to the slot from the end section for coolant liquids is enabled. In this article, a solution for in-slot and in-stator direct oil cooling for a tooth coil winding machine is presented. The coils are prewound on bobbins and inserted on the stator teeth. The novelty of the design consists in the integration of the cooling, using a thermally conductive epoxy resin to create the channels within the slot as well as the positioning of the stator yoke cooling channels. A 50-kW machine for an automotive traction application is designed, manufactured, and tested. Conjugate heat transfer simulations are used in the design process in combination with finite-element analysis for the loss mapping. The thermal model is verified with measurements at 6-L/min oil flow and 17.5 A/mm $^2$ continuous and 35 A/mm $^2$ 30-s peak. The thermal model is then used to establish a continuous operating point at 25 A/mm $^2$ .

Power battery is the core parts of electric vehicle, which directly affects the safety and usability of electric vehicle. Aiming at the problems of heat dissipation and temperature uniformity of battery module, a battery thermal management system composited with multi-channel parallel liquid cooling and air cooling is proposed. Firstly, the simulation model of composite system is established from the system level, and the corresponding thermal performance is analyzed under different ambient temperature and charge/discharge rate. Then, the thermal management system is optimized from the aspect of coolant flow direction and control strategy. The results show that changing the coolant flow direction can reduce the temperature difference of the battery module to within 3°C, but it is not conducive to controlling the maximum temperature of the battery. With the intelligent PID control strategy, the temperature of the battery fluctuates smoothly and stays between 41 and 42°C, and the temperature of the battery module is more evenly distributed with the temperature difference within 2°C.

Firefighters’ protective clothing (FPC) can limit human thermoregulation due to limited water vapor permeability and insulation. This study investigated the effect of cooling on the physiological responses and probability of hyperthermia in subjects wearing FPC during exercise in a hot environment. Twelve males participated in this study. A maximal graded treadmill exercise test was performed to measure maximal oxygen uptake ([Formula: see text]) and to assess subjects’ capacity to perform the assigned exercise. Exercise included treadmill walking at 40% [Formula: see text] in warm ([Formula: see text]) and humid (70% RH) conditions for 40 min while wearing FPC. Subjects participated in two randomly counterbalanced assigned experimental protocols: control (no cooling) and intervention (cooling). The experimental intervention consisted of a cooling garment infused with cooled water ([Formula: see text]) through silastic tubing sewn into the fabric and worn underneath FPC. Each subject served as their own control and, therefore, completed both the control and intervention of the protocol. A logistic regression model was used to analyze the interaction effect of cooling on the probability of progression to hyperthermia ([Formula: see text]). Subjects’ physiological responses increased during exercise in a warm and humid environment. Active cooling decreased (p < 0.05) the thermal stress thereby reducing the probability of hyperthermia while exercising in hot and humid conditions. The results indicate that when cooling was used each subject, on average, was 91% less likely to reach the lower threshold limit of hyperthermia. Exercise in hot environments while wearing FPC results in significant physiological strain, which may lead to hyperthermia. Utilization of a cooling garment reduced physiological strain and the probability of hyperthermia.

Data center proliferation has been increasing significantly around the world attributed to growth in technologies such as the Internet of Things (IoT), bitcoin mining, and high-performance computing (HPC). A direct consequence of these developments is an enhancement in processing units and a corresponding rise in CPU and GPU power densities. Limitations of air cooling to dissipate increasing power densities in processors have compelled the researchers to move toward better and efficient liquid cooling solutions. In an earlier study, a custom-made mini-rack with liquid-cooled 2OU (open rack Unit) web servers were tested for comparison of centralized and distributed pumping with constant flow rates at the server level. The effect of higher inlet temperature in terms of IT power, cooling power consumption, and CPU temperature was reported along with a comparison of centralized versus distributed pumping. In this article, the same 2OU server is used to show the effect of variable flow rate on server thermal performance. The parameters monitored for performance quantification are the core temperatures, dual in-line memory modules (DIMM) temperatures, and platform controller hub (PCH) temperature. These parameters were reported by varying the CPU power consumption, coolant inlet temperatures, and coolant flow rates by controlling the distributed pumps. The server was fully enclosed with no outside air intake where the CPUs were cooled by cold plates and the rest of the components with internally recirculating air. The results obtained from the experiments were compared with the results obtained from a previous study where the effect of the variable flow rate was ignored. A full-factorial design of experiments (DoE) was designed using Minitab 19 to analyze the results statistically.

Heat pipes and vapor chambers have been widely utilized for the thermal management of electronic devices due to their effective heat transport, passive cooling operation, and high reliability. In t...

Computer will overheat quickly if used in a state of full load continuously. One component on a computer that generates heat is the central processing unit (CPU) which is a key component on a computer where program instructions are processed. One of the right solutions to cool the CPU is the use of heat pipes as cooling system, using several size container, loaded with a special liquid liquid to deliver the heat from the evaporator zone to the other end called condenser zone, but because the heat pipe condenser output temperature is still high therefore a cascade heat pipe was created to lower the output temperature. In this study there are four CPU cooling systems used namely single condenser cascade heat pipe and a double condenser cascade heat pipe, while others two cooling systems as a comparison namely non-cascade heat pipe and non-cascade heat pipe with fan. This study aims to find out the cooling performance of cascade heat pipe as CPU cooling system in a small form factor desktop PC by testing variations in workload, the workload given is idle load (12W) where the processor only runs the operating system without the software load so the processor utilization is only 1% -10%. Next is the medium load (30W) that uses 2 threads with processor utilization of 50% -90%. The last workload is full load (35W) with the number of threads used being 4 with processor utilization of 90% -100%. This research found that the thermal resistance of the cascade heat pipe tended to be higher than that of the non-cascade heat pipe, however the increase that occurred was not too large compared to the resulting performance of 60.2°C in the processor and 40.4°C in the heat sink for the cascade double condenser, the operating temperature of the CPU does not increase significantly as the thermal resistance increases on the cascade heat pipe.

Recently, the development of modern vehicles has brought about aggressive integration and miniaturization of on-board electrical and electronic devices. It will lead to exponential growth in both the overall waste heat and heat flux to be dissipated to maintain the devices within a safe temperature range. However, both the total heat sinks aboard and the cooling capacity of currently utilized thermal control strategy are severely limited, which threatens the lifetime of the on-board equipment and even the entire flight system and shrink the vehicle’s flight time and range. Facing these thermal challenges, the USA proposed the program of “INVENT” to maximize utilities of the available heat sinks and enhance the cooling ability of thermal control strategies. Following the efforts done by the USA researchers, scientists in China fought their ways to develop thermal management technologies for Chinese advanced energy-optimized airplanes and spacecraft. This paper elaborates the available on-board heat sinks and aerospace thermal management systems using both active and passive technologies not confined to the technology in China. Subsequently, active thermal management technologies in China including fuel thermal management system, environment control system, non-fuel liquid cooling strategy are reviewed. At last, space thermal control technologies used in Chinese Space Station and Chang’e-3 and to be used in Chang’e-5 are introduced. Key issues to be solved are also identified, which could facilitate the development of aerospace thermal control techniques across the world.

Optimization of heatsinks has a critical importance for the energy-efficient cooling of high-performance computing (HPC) servers to meet reliability, performance, and cost targets. This article provides a detailed application of the effectiveness as a performance metric to provide a qualitative comparison of the CPU heatsink solutions. First, the use of effectiveness as a metric to provide an absolute performance of heatsinks on a simple scale of 0–1 is highlighted. Then, the effectiveness and thermal resistances are compared to explore the limits of air cooling and the relative merits of liquid cooling. Second, a response surface method (RSM) for the heatsink optimization is presented. Furthermore, a response surface optimization (RSO) based on the design of experiments (DOE) is performed on the numerical models of the heatsink and cold plates using FloTHERM computational fluid dynamics (CFD) software. The simulation results obtained at 45 °C inlet are used to provide an objective comparison among the optimum heatsink and cold plates. The simulations show that heatsinks have the effectiveness of 0.65–0.75 and a cooling capability of 150–250 W. The cold plates have an effectiveness of 0.25–0.30 and a cooling capability of 325–425 W. Furthermore, the simulation results are compared with benchmark validation studies. Counterintuitively, the higher effectiveness obtained for the air-cooled heatsinks indicates limited scope for further improvement, whereas the cold plates (with lower effectiveness) provide great scope for further improvements to meet future cooling challenges.

The results of experimental research and thermal analysis of several types of cooling of brushless electric motors with nominal power 10-12kW (PMAC), suitable for ?light? EV/HEV vehicles are presented in the research paper. The studied motors have permanent magnets, a double stator and an axial magnetic flux with air or liquid cooling. The Motor-CAD software performed the presented thermal analysis. The experimental study was made on the basis of precision results, obtained from the measurement of process temperatures during operation in a real-world environment. For this purpose, the electric motors were equipped with a number of thermocouples with which the temperatures are measured. The precise measurement and recording of the heat flux temperatures is performed using LabVIEW software. The calculations from the thermal analysis coincide with the experimental results and can be used to predict the heat fluxes in different designs and types of cooling systems. The possibilities for improving the cooling and power of standard PMAC electric motors with double stators have been studied and analyzed.

The solenoid pulse inductor is a key component of the electromagnetic launch (EML) system, and effective thermal management is a necessary condition for reliable and stable operation under continuous discharge condition. A 3D transient coupling heat transfer model for the solenoid pulse inductor with liquid cooling mode was established, and the temperature distribution and the characteristics of heat dissipation of the inductor under continuous discharge condition has been analyzed. A temperature measurement system was designed, and the accuracy of the 3D coupling model has been verified. In addition, effects of the flow rate, the inlet temperature and the coolant on the efficiency of liquid cooling were analyzed by using this model. The results show that during continuous discharge, the maximum temperature and maximum temperature difference of the inductor continue to increase, but the rising speed rapidly slows down. Raising the flow rate can effectively improve the efficiency of the liquid cooling and decrease the temperature difference in the inductor during continuous discharge, but the marginal benefit of raising the flow rate is gradually reduced. Dropping the inlet temperature has little effect on the efficiency of the liquid cooling, and ethylene glycol solution can replace deionized water as the liquid cooling coolant for the pulse inductor under low temperature condition. This paper is expected to help to improve the thermal management and optimize the performance of the solenoid pulse inductor.

Data centres (DCs) are often provided with adequate air conditioning units to meet cooling needs. Failure free operation is the primary goal of any DC, as equipment failure in a DC is very expensive. If inefficiencies involved in heat removal process can be reduced, there will be a significant reduction in energy consumption. This paper provides a review of existing air cooling and liquid cooling techniques to remove the heat from the DCs effectively. It includes the potential viability of free cooling & reusing heat for other applications.

The drastic technological growth and development of advanced computer processors leads to a serious problem due to the generation of heat. Modern processors are designed in such a way that even though small in appearance their performances are beyond our thought. The performance of processors directly depends on the heat they generate. The heat generated while processing is generally considered as waste heat that needs to be removed immediately before it could fail the heat sensitive components present inside the processor. There comes a problem of removing this waste heat. Bridge Rectangular Fin Heat sink (BRFHS) is an object having a single base and fin-like protrusions made of aluminium and pyrolytic graphite material because of their high thermal conductivity. ANSYS Fluent CFD Version 12.1 software package was used for simulation. Air is used as a fluid and a comparative study was done for the same heat sink configurations between the aluminium and pyrolytic graphite. In this work, the effect of angle of fin changes was also analysed for aluminium and pyrolytic graphite. It was found that at a fluid velocity of 1.2 m/s, the maximum fin temperature for aluminium was 320 K while and that for pyrolytic graphite was 310 K. The optimum cooling is achieved by BRFHS having an angle of 22.5° simulated with pyrolytic graphite material at 1.2 m/s air velocity. The maximum temperature found on the fin after dissipation of heat was 302 K which is very near to the ambient temperature.

In titanium alloy processing, the cutting fluid often expresses the environmentally unfriendly, high-cost, and limited-quality improvement and affects their future application prospects. At present, liquid nitrogen (LN2) cooling could play a green manufacturing role and is being popularized for difficult-to-machine materials. In this paper, an LN2 inner injection transmission device was fabricated. A series of processing tests were carried out by comparing the LN2 external spray method and cutting fluid. And the different effects of the two LN2 cooling methods on the machining accuracy, required liquid nitrogen flow, machinability, and tool wear were investigated. The results show that the cryogenic of LN2 can significantly improve the thermal and force coupling action conditions in titanium alloy processing than cutting liquid cooling. Compared with higher cutting zone temperature of cutting liquid cooling, it is lower than 0° C for LN2 cooling even at 300-m/min cutting speed. When the required cooling temperature is lower, the external spay method needs more than 200% flow than the inner injection. Meanwhile, the diameter of 6-mm spray nozzle should be selected to be the more effective one for the external spray method. Moreover, the tool life can be more than 200% in LN2 cooling, especially the inner injection cooling is 10% longer than that of the external spay one. The milling force of external spay cooling is increased compared with inner injection. Furthermore, the inner injection cooling of LN2 has more efficiency, environment friendliness, and cleaner production for the machinability of difficult-to-machine materials.

Natural circulation loops (NCLs) are mainly consists of three sections i.e., Heat source, heat sink, and adiabatic section. The working fluid in the NCL flows due to density difference caused by the temperature difference between the heat source and heat sink. Single-phase NCLs are used in many types of energy systems, such as solar heaters, nuclear reactors, geothermal power production, engine and computer cooling. Most of the engineering devices are operated with transient heat flux which creates the problems like thermal instabilities and shortage of energy supply. Phase change materials were used for thermal energy storage applications. Thermal energy storage is required to diminish the gap between demand and supply by storing the extra thermal energy during the charging time and utilized in peak time. The current work presents a novel method of integrating phase change materials (PCMs) within the evacuated solar tube collectors of a Single-Phase natural circulation loop (SPNCL) for reducing the instabilities. In this method, the Heat Transfer Equipment (HTE), the pipe is integrated with phase change material, where heat is effectively accumulated and stored for an extended period of time due to thermal insulation of evacuated tubes. The benefit of this method includes improved functionality by delaying release of heat, thus providing heat during the hours of high demand or when the solar intensity is insufficient. The work compares the experimental data with and without Phase Change Material. The experiment is performed for various flow rates and various heat fluxes. SPNCL with PCM evaporator shows the best thermal performance compare to the without PCM.

This research was performed to test the effectiveness of the microclimate body cooling system which belongs to the group of active systems with liquid-cooled technology. The liquid cooling vest efficiency was observed concerning the physiological fitness of the standard protective set used in specific environmental conditions which imply increased thermal strain of the test subjects. Experimental results from the research are based on the examinations carried out in a thermo-physiological laboratory. Ten healthy male volunteers ? test subjects aged (23.4 ? 2.4 years, weight 74 ? 7 kg, and height 184 ? 9 cm) were exposed to thermal strain testing (40 ?C temperature, 40 ?3 % relative humidity, without wind) and simultaneously to physical effort caused by walking on the treadmill at a speed of 5 km/h, during 45 minutes. Tests were performed in two variants: without any cooling system and with the KewlFlow Circulatory Cooling Vest with Cooler Kit. Throughout heat exposure, the subject?s body core temperature (tympanic temperature ? Tty), mean skin temperature, Tsk, and heart rate were measured. Furthermore, sweat rate was calculated in order to determine all changes in the water and electrolyte status. Experimental results confirm that the results of this study have recognized the benefits of a liquid-cooled vest in lowering the thermal strain.

Electrical power recovery from waste heat released during active cooling of 100–200 °C solids is of great importance because such situations are common in our world. However, the concept of simultaneous liquid cooling and electric power generation has been barely explored, apart from a few preliminary studies that showed power generation densities of only 0.05–0.5 W m−2. Here, we report a realistically useful power generation density of 10 W m−2 during liquid forced convection cooling of a 170 °C surface, thus demonstrating the feasibility of such a concept, based on thermogalvanic conversion with a redox couple. This was achieved by exploiting the fluid dynamics based on a microchannel concept, where a thin thermal boundary layer is formed on the hot surface, enabling both high cooling efficiency and large interelectrode temperature difference (>100 K). A new γ-butyrolactone-based high density electrolyte with sufficient stability against flame contact was used. Our combined cooling and thermogalvanic cell was able to continuously light LEDs and run air fans despite the small electrode area. Large values of heat transfer coefficient, up to 1160 W m−2 K−1, were achieved. At all flow rates tested, the electrical power obtained was 10 to 1000 times larger than the hydrodynamic pumping work required to force the liquid through the cell, that is, gain ≫1. Thus, this technological concept has been shown, for the first time, to be a feasible option to recover electrical power from the waste heat released during cooling of 100–200 °C surfaces, which are widespread in our world.

Electric vehicles that run on batteries have a major disadvantage of temperature abnormalities when operated at extreme working conditions. Therefore, thermal management of battery pack is essentia...

Lithium-ion battery (LIB) nowadays plays a key role as one of the most widely used energy storage technologies such as the application in electric vehicles. Thermal management critically affects the performance of LIB. Phase change cooling using phase change material (PCM) has become a promising method due to its high latent heat and no need to consume extra pump power. In this study, thermal performance of a battery module with 25-parallel 18650 lithium-ion battery has been numerically and experimentally investigated by adopting phase change cooling with PCM. Firstly, the internal resistance of the unit cell has been experimentally tested to build up the heat generation model. Based on the heat generation model and heat transfer model, the effects of PCMs thermophysical parameters including thermal conductivity, latent heat and porosity are investigated when they are applied in the thermal management of designed LIB module. The results indicate that the higher thermal conductivity and latent heat lead to better thermal management performance comprehensively considering the maximum temperature and temperature uniformity of LIB module. Results also illustrate that thermal management performance increases very slightly when the thermal conductivity and latent heat attain a relatively high value. As for the porosity of paraffin/metal foam, an optimal value of 94% exists to achieve the lowest maximum temperature for LIB module.

The paper considers the possibility of intensifying isothermal holding processes during quenching of high-strength cast irons by using an external source of physical impact in the form of ultrasonic waves. For experimental evaluation of this effect in the laboratory of MiAM of the Physical-Technical Institute of the National Academy of Sciences of Belarus, prototypes of highstrength cast irons were cast in an ISV 0.004 crucible induction furnace. A mixture of NaNO2 and KNO3 salts in a 1:1 ratio was used as a liquid cooling medium during quenching. Ultrasonic treatment of the salt melt during the cooling of the samples was carried out using an UZG-20–15 generator in cooperation with the ITA of NAS of Belarus. The mechanical properties and structure of the treated cast irons were determined both in the cast state and after isothermal quenching.To study the effect of ultrasonic treatment of the quenching bath on the formation of the structure and properties of highstrength cast irons during isothermal quenching, a number of comparative experiments were carried out, consisting in cooling the samples from 910 °C to 350 °C with and without the use of dynamic waves to the bath. With the help of metallographic analysis, measurements of hardness and friction coefficient, the beneficial effect of ultrasonic treatment of the cooling medium on the structure and properties is shown, which is reflected in an increase in the uniformity of the distribution of hardness over the cross section of cast iron and in its wear resistance, as well as a reduction in the isothermal holding time by up to two times.