Search

• New sintering method for manufacturing Cu microchannels with multilayers of channels. • Pressure drop significantly lower than LCS porous Cu. • Heat transfer coefficient higher than the conventional machined microchannels. Microchannels have many thermal management applications due to their high heat transfer performance. In this paper, sintered Cu microchannels with well controlled channel diameters of 450 µm, 390 µm and 290 µm, and volume fractions of channels of 0.1, 0.2, 0.3 and 0.4, were manufactured by a new method and their pressure drops and heat transfer coefficients were compared with conventional machined Cu microchannel and porous Cu manufactured by Lost Carbonate Sintering (LCS). The pressure drops of the sintered Cu microchannels were higher than a conventional machined microchannel, but significantly lower than LCS porous Cu samples. The sintered Cu microchannels achieved a similar range of heat transfer coefficients as the LCS porous Cu, with much lower volume fractions of channels. They had higher heat transfer coefficients than the conventional machined microchannel, mainly due to the introduction of multilayers of channels in the metal matrix. Darcy-Weisbach and Sieder-Tate equations with the introduction of appropriate correcting factors can be used to estimate the pressure drop and heat transfer coefficient of the sintered Cu microchannels. There exists a strong correlation between heat transfer coefficient and pumping power. [ABSTRACT FROM AUTHOR]

Power electronic devices and applications are striving toward more compact designs with high-power density. This has been enabled by the high switching speed of wide bandgap devices, such as silicon carbide (SiC) and gallium nitride (GaN) when compared to silicon. In order to take advantage of the high switching frequency, there is a need for small multichip packages with low stray inductance. This paper describes the experimental evaluation of a novel quad flat no-lead (QFN) power module with SiC power transistors. The module was designed to feature low stray inductance in a small-sized package and incorporate low-cost packaging technology. Currently available solutions are either expensive large high-power modules on the one hand or discrete packages with higher stray inductance on the other hand. The proposed QFN module aims at combining the electrical performance of a module with the cost benefit of a discrete. This paper presents the proposed module’s design and fabrication and shows, through simulations and experiments, its thermal and electrical performance when it is used in a 400-V, 1.2-kW buck dc–dc converter. [ABSTRACT FROM AUTHOR]

Fe 2 (SO 4) 3 was investigated as an additive to improve the thermal stability of the positive electrolyte for an all-vanadium flow battery (VFB). The effects of the Fe 2 (SO 4) 3 addition on the electrochemical activity, capacity, and charge/discharge cycle performance were also studied. The addition of Fe 2 (SO 4) 3 significantly enhanced the thermal stability of V(V) in the positive electrolyte. For a positive electrolyte consisting of 2.0 M vanadium ions, the addition of Fe 2 (SO 4) 3 within the concentration range of 0.5–0.7 M enabled the electrolyte to remain stable for more than 168 h at 50 °C. Cyclic voltammetry (CV) measurements showed that the peak positions of the Fe2+/Fe3+ and VO2+/VO 2 + couples did not cross each other, indicating that the Fe 2 (SO 4) 3 addition did not lead to any side reactions. Electrochemical impedance spectroscopy (EIS) analysis revealed that the addition of Fe 2 (SO 4) 3 led to a slight increase of the electrolyte ohmic resistance and reduction of the charge-transfer resistance on the carbon electrode. Both the CV and EIS results indicate that Fe 2 (SO 4) 3 had no adverse effects on the reversibility or electrochemical activity of VO2+/VO 2 +. The capacity for battery charge/discharge cycles hardly changed compared with that of the pristine electrolyte during operation for over 360 h at 50 °C. The improved vanadium positive electrolyte with the Fe 2 (SO 4) 3 addition is expected to be used for practical applications. The Fe 2 (SO 4) 3 addition can extend the VFB operation temperature to 50 °C, thus reducing the cost of thermal management of the energy storage system and improving the technical and economic performance of VFBs. Schematic diagram of a vanadium flow battery using the improved vanadium positive electrolyte, in which Fe 2 (SO 4) 3 was used as stabilizer to enhance the thermal stability of V(V) in the positive electrolyte, thus leading to VFB reliable operation at 50 °C. Image 1 • High-concentration Fe 2 (SO 4) 3 was used as an additive for VFB positive electrolyte first time. • The addition of Fe 2 (SO 4) 3 stabilizes the vanadium electrolyte at 50 °C. • No adverse effects were found on reversibility and electrochemical activity of VO2+/VO 2 +. [ABSTRACT FROM AUTHOR]

The SCO2 (supercritical carbon dioxide) Brayton cycle has been recommended to the marine industry due to its high efficiency, small volume and low weight. However, the undulation and sway of ships aroused by the wind and sea waves in the marine environment may generate the periodic changes in multiple forces, and finally leading to the unstable performance of the SCO2 Brayton cycle. Phase change material (PCM) system grabs much attention for its large heat storage capacity and stabilized operation temperature, and has a wide application in the thermal management system, especially for the temperature control of a thermodynamic cycle. In this work, a PCM system is introduced into SCO2 recompression Brayton cycle in order to reduce the response amplitudes of inlet temperatures in main compressor and recompressor. The transient characteristics of cycle parameters affected by the PCM system in a high frequency oscillating environment are studied. The transient analyses indicate that PCM system is able to control the temperature changes and helpful to enhance the stability of cycle performance. [ABSTRACT FROM AUTHOR]

• Application of MH hydrogen storage in PV and FC based microgrid. • Dynamic modelling of MH storage. • Design of thermal management for MH storage with electrolyzer and FC applications. • Effect of thermal management on the dynamic discharging characteristics of MH. In this paper, experimental and simulation study provides a detail analysis of operational characteristics for hydrogen charging (5 kW p photovoltaic + 0.6 kW electrolyzer + 5000 L metal hydride (MH) storage) and discharging (1 kW proton exchange membrane fuel cell (PEMFC) + MH storage) units in a microgrid. Hydrogen charging and discharging processes in MH storage are exothermic and endothermic in nature, respectively, therefore, a suitable thermal management (cooling/heating system) is required. The simulation model of given metal alloy (LaNi 5), size and storage capacity of MH cylinder helps to predict the potential of dynamic charging and discharging rates with change in the external cooling/heating management and therefore to design the suitable thermal management system. Results show that dynamic variation in the discharging rate from the MH depends on the management of the external heating system, amount of stored hydrogen, operating temperature and pressure of MH cylinder. The hydrogen discharging rate up to ≈60 L per minute (lpm) can be obtained at 50 °C temperature and 1 lpm flow rate of external heating water. 5000 L MH storage is capable to provide the stable hydrogen supply (≈12 lpm) for ≈1 kW PEMFC generator operation up to ≈5.5 h with heating system (30 °C inlet temperature and 1 lpm flow rate of water). Dynamic operational characteristics of MH storage with electrolyzer and PEMFC show that the appropriate use of designed thermal management system facilitates the proper functioning of overall system. [ABSTRACT FROM AUTHOR]

The purpose of this paper is to review the recent literature regarding the effects of low temperatures on Lithium ion (Li-ion) batteries for electric vehicle, plug-in hybrid electric vehicle, and hybrid electric vehicle applications. Special consideration is given to nine major effects that directly or indirectly impact the battery use at low temperatures and it is presented that they are correlated to each other. The main discussions in this paper are capacity loss, power loss, life degradation, safety hazard, unbalanced capacity, charging difficulty, thermal management system complexity, battery model and state estimation method complexity, and incremental cost. The effects correlations and possible solutions are explained to provide a detailed, yet broader understanding of the Li-ion batteries low-temperature operating scenarios. [ABSTRACT FROM AUTHOR]

Thermal analysis is a key aspect in electrical machine design and for those operating with severe duty where a high-reliability thermal analysis is required. This paper presents a comprehensive analysis of techniques for calibrating generic thermal model of electrical machines. The proposed approach combines two existing experimental methods commonly used in thermal testing of electrical devices. The first method uses a short-duty transient excitation to derive the winding thermal parameters, whereas the second method uses a steady-state excitation to estimate the thermal parameters related to the heat transfer from the winding. Both experimental methods are based on a well-defined heat source provided by a constant current (dc) excitation. For reference, alternative existing methods for calibrating thermal models, are usually combining the winding thermal data predictions and a set of experimentally derived temperatures from dc tests. Such approach, however, might be inadequate if not supported by extensive experimental data. This frequently leads to a significant rate of inaccuracy, thus having a significant impact on the reliability of temperature predictions. The main advantage of newly proposed approach is the reducing of the number of variable parameters and a more systematic calibration process. Additionally, a detailed test procedure for generic thermal model calibration is presented and discussed. [ABSTRACT FROM AUTHOR]

• Effects of varying orientation, and over height ratio on PCM-PV system performance. • Rising the over height ratio reduces the stratified liquid layers to avoid hot spots. • Using 60% over height ratio attains the best CPV-PCM performance. A new concentrator photovoltaic system integrated with phase change material heat sink is developed to achieve low and uniform temperature distribution along the solar cell. The developed system includes a phase change material enclosure with different over height ratios, defined as the ratio between the over height length of the phase change material heat sink to the solar cell length. Subsequently, four different over height ratios of 0, 20, 40, and 60 % along with three inclination angles of −45°, 0° and 45° at solar concentration ratios of 5 and 10 are investigated. Thus, experimental and numerical investigations have been carried out to investigate the influence of the over height ratio and inclination angle of the phase change material heat sink on the temperature distribution along the solar cell. To assess the performance of the suggested designs of heat sinks, a compendious two-dimensional model of the concentrator photovoltaic cell layers combined with phase change material is developed and numerically simulated. The numerical results are further validated with experimental measurements. These measurements involve transient variation of liquid fraction and the evolution of the local temperature during melting of RT35HC phase change material carried out at different inclination angles of −45°, 0° and 45°. Results indicate that the influence of varying the over height ratio depends on the inclination angle of PCM heat sink. It is found that at an inclination angle of −45° and a concentration ratio of 5, the peak cell temperature reduces from 92 to 74 °C, and the temperature uniformity varies from 13.7 to 5.3 °C as the over height ratio rises from zero to 60 %. However, at an inclination angle of 45° only, a slight reduction in the peak cell temperature is observed along with a minor improvement of temperature uniformity. Results of the present work can assist in the selection of appropriate phase change material -heat sink design for the required types of solar concentrators. [ABSTRACT FROM AUTHOR]

Thermal behavior and solid electrolyte interphase (SEI) are crucial topics for the development and operation of the lithium-ion battery. To investigate the thermal behavior and SEI formation in a lithium-ion battery (C-LiMn 0.5 Ni 0.3 Co 0.2 O 2), a numerical method combining the pseudo-two-dimensional electrochemical model, heat transfer model, and capacity fading model is developed. For the battery operated at a low C-rate, the ohmic heat and the reversible heat dominate the heat generation at a low state of charge (SOC) and high SOC, respectively. Alternatively, the ohmic heat is the dominant factor causing heat generation at a high C-rate. The reversible heat reaches a maximum at the SOC of 65% due to the entropic coefficient of the cathode active materials. The SEI thickness increases around 70 nm with increasing the C rate cycling. The heat generation is the bottleneck for the resistance of Li+ ion conductivity at the SCI. The heat generation of the cathode is larger than that of the anode, which is caused by the low solid phase conductivity of the cathode. This analysis has provided useful insights into the thermal management of lithium-ion battery in the course of charging and discharging which is conducive to the development and safe operation of the battery. • A numerical method model is developed to investigate thermal behavior of a Li-ion battery. • Heat generation at a low C rate is mainly contributed by the reversible heat at high SOC. • Ohmic heat dominates heat generation at a high C rate. • Heat generation of the cathode is larger than that of the anode. • SEI thickness increases around 70 nm with increasing the C rate cycling. [ABSTRACT FROM AUTHOR]

A single-phase high power electronics package is designed and developed in this paper. The developed power package achieves a significant thermal performance improvement compared with the conventional wire-bonded power package. The improvement is attributed to two features of the package design. First, the SiC chips are embedded into the active metal brazed (AMB) substrates with specially designed cavities, as such the heat transfer path from the embedded SiC chips to the liquid-cooled heat sink attached to the bottom side of the AMB substrate is shortened. Hence, the thermal performance of the package is improved. Moreover, customized copper clips are introduced as the electrical interconnections between the SiC chips and the top metal layer of the substrate at the same level, and the top surface of the power package remain flat. As such another heat sink can be added to the top side of the package to further improve the thermal performance of the power package through the double-side cooling (DSC) scheme. The simulation results show that the junction-to-case thermal resistance (Theta JC) of the optimized power package is about 50% less than the Theta JC of the conventional wire-bonded power package with the same package size and the same power rate. Further applying the DSC scheme to the proposed power package, which is not suitable to the conventional wire-bonded power package, the Theta JC of the proposed power package reduces another 20%. In addition, the effects of the core layer (i.e., material and thickness) and the metal layer (i.e., materials and thicknesses) of the AMB substrate, as well as the die attach (i.e., material and thickness) on the Theta JC of the proposed power package are investigated systematically. As such the thermal performance of the power inverter package is further elaborated. Finally, the thermally enhanced power package is fabricated and assembled. Thermal characterization has been conducted, and the thermal performance of the developed power package has been evaluated. The simulation results and characterization results match well with each other. [ABSTRACT FROM AUTHOR]

Polymer-based composites with excellent heat transfer properties have been widely applied in the thermal management system. However, the poor dispersion of filler restricts the heat dissipation performance of composites and the strong interfacial thermal barrier is another crucial issue. Herein, core-shell-structured polystyrene@multiwalled carbon nanotubes (PS@MWCNTs) composites were prepared by a one-step microemulsion polymerization method. The resultant PS@MWCNT composite with interconnected MWCNTs on the surface, as a thermally conductive network, was further processed and formed via hot pressing. As a consequence, the high thermal conductivity of 1.357 W/m K was achieved at MWCNTns loading of 10 wt%, which is equivalent to a thermal conductivity enhancement of 618% compared to pure PS (0.189 W/m K). Besides, the obtained PS@MWCNT composite film also possesses a low sheet resistance. This method can be further extended to construct other polymer-based composites with high thermal conductivity. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • The single battery model is representative of the battery module at large flow rate. • Characteristic melting stages are identified for novel conjugated cooling of battery module. • Conjugated cooling can significantly reduce the battery temperature and ramp-up rate. • Increasing thermal column size or heat spreading plate thickness improves heat dissipation significantly. • Good agreement is found between numerical analysis and experimental test. Abstract A novel conjugated cooling configuration using phase change material (PCM) and liquid cooling techniques is proposed, and its thermal performance is investigated for a battery module. 106 cylindrical batteries are connected to the cold plate at the bottom through a heat spreading plate and the adjacent thermal columns, with PCM filled in between the gaps, which forms the cooling configuration. Three-dimensional numerical models are established for the cooling of the representative battery and battery module, which includes the battery connected to a liquid cooled mini-channel cold plate through the heat spreading plate and thermal column structures. The thermal characteristics of the battery incorporating the PCM melting and liquid cooling are examined at large flow rate. The geometrical parameters such as the size of the thermal column, the thickness of the heat spreading plate and the spacing of the batteries are investigated for the present conjugated cooling configuration. Both the battery temperature ramp-up rate and the steady-state battery temperature are significantly reduced by the conjugated cooling, in comparison with single PCM or liquid cooling conditions. The effects of various structure parameters on the thermal performance can be visualized by plotting the working time t 50 vs the heat density based on the PCM volume. A comparison of the numerical simulation with the preliminary experiment work shows good agreement. This work can be useful in the design of conjugated configurations for the battery thermal management. [ABSTRACT FROM AUTHOR]

In order to obtain composites which can meet the requirements of current thermal management materials, a new family of ternary aluminum matrix composites has been recently developed through vacuum gas pressure infiltration. Carbon fiber (CF) and graphite flake are both used in the composites as reinforcements, among which CF plays a role in strengthening the aluminum matrix and graphite flake plays a role in enhancing the thermal conductivity (TC) of the composites. Both of them were coated with chromium uniformly using salt bath coating to improve the wettability between the matrix and reinforcement, which were proved by the micro-structural characterization. The effects of different volume of chromium coated CF on the thermal–physical properties and mechanical properties of the composites were investigated, from which we could conclude that CF could not only dramatically increase the mechanical properties of the composites, but also can space apart the graphite flake layers for infiltration. What's more, a Fricke prediction model was adapted to estimate the TC of the composites, and the reasons of the gap between the measured value and prediction model were systematically analyzed. [ABSTRACT FROM AUTHOR]

Highlights • A practical galinstan based minichannel cooling system was developed, which can dissipate heat 300 W/cm2 and 1500 W. • The thermal performance and hydrodynamic characteristic of galinstan based minichannel heat sink was evaluated. • The heat capacity thermal resistance was an important factor for galinstan based minichannel cooling. • The pressure losses of galinstan minichannel heat sink was far lower than the water microchannel heat sink. • This cooling system can operate silently, steadily and smoothly. Abstract This paper is dedicated to experimentally investigate the liquid galinstan based minichannel cooling for high heat flux and large heat power thermal management. Firstly, a compact electromagnetic pump towards effectively driving liquid metals was developed, which can provide high pressure head up to 100 kPa. Then, the minichannel heat sink was designed and manufactured, with width of channel 1 mm, height of channel 5 mm. Furthermore, the galinstan based minichannel cooling system was established and experimentally tested under different heating loads and pumping powers. The results show that galinstan based minichannel cooling system can dissipate heat with heat flux 300 W/cm2 and heat power 1500 W. And the thermal performance and hydrodynamic characteristic of minichannel heat sink using galinstan as coolant were obtained. It indicates that compared to water based minichannel cooling, galinstan based minichannel cooling can obtain a rather larger heat transfer enhancement, and the pressure losses of galistan based minichannel heat sink is much lower than that of water based microchannel cooling. Moreover, it is also found that heat capacity thermal resistance becomes a rather important factor for the thermal performance of galinstan based minichannel, due to the high thermal conductivity and lower heat capacity of galinstan. Furthermore, the galinstan based minichannel cooling system can operate silently, steadily and smoothly by using electromagnetic pump, which has no moving parts. Overall, the galinstan based minichannel cooling is proven to be a powerful and practical way for the thermal management of high heat flux and large heat power devices. [ABSTRACT FROM AUTHOR]

Highlights • Nanoscale heat pipes composed of nano-grooves are simulated using molecular dynamics. • Performance is evaluated based on operating parameters (filling ratio, heat load). • Scale effects on the working characteristics and performance are elucidated. Abstract Passive thermal spreaders utilizing liquid/vapor phase-change mechanism such as heat pipes, have been widely used in the macro-scale thermal management of electronic devices for many years. Micro-fabrication techniques enabled the fabrication of micro-scale grooved heat pipes on semiconductors. Recent advances in fabrication techniques, on the other hand, enabled production of nano- and ångström-scale capillaries and cavities, which renders the manufacturing of nanoscale heat pipes possible. In the present study, we have simulated nanoscale heat pipes composed of nano-grooves using molecular dynamics and evaluated their performance based on different operating parameters such as the filling ratio and heat load. Moreover, evaluation of size effect on the thermal performance is made by comparing proportionally scaled heat pipes. Simulation results reveal that efficient operation of nano-grooved heat pipes depends not only on the proper selections of filling ratio and heat load, but also on the geometrical parameters such as cross sectional dimensions and aspect ratio of the groove. The modeling strategy used in this study opens an opportunity for computational experimentation of nanoscale heat pipes. [ABSTRACT FROM AUTHOR]

Highlights • Fish-scale-like structured BN was synthesized by spray drying and pyrolysis. • BN microrods exhibit high suspensibility and long-term stability in water. • BN/water fluids possess excellent tribological properties. • The thermal conductivity of 0.1 vol% BN/water fluids is up to 1.117 W/m K. Abstract Hexagonal boron nitride (h-BN) has triggered great interest in thermal management system because of its superb thermal conductivity, excellent chemical inertness and outstanding tribological behavior. However, the application of BN in water suffers from the poor dispersion stability. Herein, we develop a spray drying and pyrolysis route to directly fabricate porous BN microrods with fish-scale-like structures. BN microrods exhibit long-term dispersion stability in aqueous solution due to their high hydroxylation degrees. Although the viscosity of water was increased after adding BN microrods, the friction coefficient and wear scar diameter were reduced obviously. Moreover, thermal conductivity of BN/water fluid was improved from 0.589 to 1.117 W/m K when the content of BN was 0.1 vol%, which was higher than that of previous results. These results demonstrate that the fish-scale-like structured BN microrods have great potential and irreplaceable advantage in thermal and tribological management. [ABSTRACT FROM AUTHOR]

Highlights • Nanoparticle distribution in the nanofluid, preparation methods and degradation processes (aging) were studied. • The nanoparticles/water nanofluid is employed as the working fluid of the loop thermosyphon. • Using nanofluid, heat transfer in a loop thermosyphon was improved. Abstract This research focuses on two-phase thermal control systems, namely loop thermosyphons (LTS) filled with nanofluids and their use as LED cooling devices. The behavior of the fluid in the thermosyphons and the mechanisms explaining the possible impact of nanoparticles on the thermal properties of the working fluid, as well as the processes in the LTS, are addressed. Nanoparticle distribution in the nanofluid, methods of preparing nanofluids and the nanofluid degradation processes (aging) are studied. The results are obtained from a set of experiments on thermosyphon characteristics depending on the thermophysical properties of the working fluid, filling volume, geometry and nanoparticle mass concentrations. The impact of nanofluids on the heat-transfer process occurring inside the thermosyphon is also studied. The results indicate the strong influence of nanoparticles on the thermal properties of the thermosyphons, with up to a 20–25% increase in the heat transfer coefficient. It is shown that this effect is due to the aggregation of nanoparticles and the formation of a micro/nano relief on the vaporization surface. Additionally, a method of calculating the hydrodynamic limit of the LTS is proposed, which allows for estimation of the maximum heat that can be transferred by means of the LTS. The nanofluids are shown to be effective means for enhancing heat transfer in two-phase thermal management systems. [ABSTRACT FROM AUTHOR]

Highlights • Battery cell spacing distribution of the parallel air-cooled BTMS is optimized. • Optimization is conducted by a strategy for homogenizing the airflow rates. • An adjustment coefficient is introduced to improve the optimized result. • Cooling efficiency of the BTMS is improved remarkably after the optimization. • The present optimized results are better than the ones in previous studies. Abstract In this paper, the cell spacing distribution of the battery pack in the parallel air-cooled BTMS is designed to improve the cooling efficiency of the system. The flow resistance network model is used to calculate the airflow rates in the cooling channels. A modification factor is introduced to reduce the error of the model. The effectiveness of the model is verified by the computational fluid dynamics (CFD) calculation, and the CFD method is validated by the experimental air-cooled system with aluminum blocks. Combining with the improved flow resistance network model, an optimization strategy is adopted to optimize the battery cell spacings for the homogenization of the airflow rates among the cooling channels. Then an adjustment coefficient is introduced to adjust the airflow rates in the cooling channels for more uniform cell temperatures. The results of typical numerical cases indicate that the cooling efficiency of the BTMS is improved remarkably after the cell spacing optimization using the developed strategy. Compared to the original BTMS, the maximum temperature of the battery pack for the optimized BTMS is reduced by about 4.0 K, and the maximum cell temperature difference is reduced by more than 69% for various inlet airflow rates. Compared to the optimized BTMS in previous study, the maximum cell temperature difference for the present optimized BTMS is reduced by more than 25% for various inlet airflow rates. [ABSTRACT FROM AUTHOR]

Highlights • Investigation of conjugate heat transfer a two-phase microchannel array. • High flux (1 kW cm−2) boiling of R134a in a channel. • Low flux correlations evaluated for accuracy by comparing to experiments. Abstract Microchannel flow boiling is an attractive thermal management strategy for ever-growing volumetric heat dissipation demands associated with electronic systems. Due to difficulties related to measurement at the microscales, the majority of researchers have chosen to study relatively simple situations with uniform heat flux. However, many applications involve local hotspots which give rise to highly non-uniform heat flux and temperature gradients due to heat spreading. This necessitates the consideration of conjugate heat transfer for accurate analysis. The current work is aimed at investigating conjugate heat transfer in a two-phase microchannel array. Experimental data was collected on R134a flow boiling heat transfer for very small hydraulic diameter (<100 µm) silicon microchannels with very high heat fluxes (>1 kW cm−2) applied via platinum strip heaters with a footprint size of 1 cm × 1 mm. The collected experimental data was then combined with detailed computational modeling utilizing finite element modeling with COMSOL Multiphysics and MATLAB to examine the applicability of five published heat transfer correlations for use in determining local heat transfer coefficients. A two-phase correlation from Agostini and Bontemps, developed for markedly different test parameters, provided the best computational agreement with an RMS temperature difference from experiment of 3.3 °C and a predicted peak perimeter-averaged heat transfer coefficient of 116 MW m−2 K−1. Modeling confirms the presence of highly non-uniform local heat flux and correspondingly non-uniform local heat transfer coefficient. The results of this study make clear the need for better micro-scale two-phase correlations developed to predict local heat transfer coefficients at these small scales and high local heat fluxes. [ABSTRACT FROM AUTHOR]

Highlights • Quantified HTC and CHF values for R−245fa at low saturation temperatures (−50°C). • Enhanced boiling heat transfer using microporous-enhanced surfaces. • Developed HTC and CHF correlations for plain and microporous surfaces. • Improved thermal management for hydrogen vehicle fueling stations. Abstract Experiments were conducted to measure the pool boiling performance of saturated R-245fa at low saturation temperatures (−30 °C, −40 °C, and −50 °C). Horizontally oriented cylindrical heat sources were used as the test samples and were intended to simulate a small section of a hydrogen-filled tube. Measurements evaluated the effects of saturation temperature and two microporous coatings on heat transfer coefficients (HTC), critical heat flux (CHF), and boiling incipient superheat. Results show that boiling performance decreases as the saturation temperature reduces—a result of less active nucleation sites and higher vapor coverage of the heated surface at lower temperatures. Microporous coatings increased HTCs and CHF values, but did not have a significant effect on reducing the boiling incipient superheat. The experimental results were used to develop correlations for nucleate pool boiling on plain and microporous surfaces that can be used to predict HTCs and CHF values at low saturation temperature conditions (down to −50 °C). [ABSTRACT FROM AUTHOR]

Intrinsic limits to temperature-dependent substrate loss for GaN-on-Si technology, due to the change in resistivity of the substrate with temperature, are evaluated using an experimentally validated device simulation framework. Effect of room temperature substrate resistivity on temperature-dependent coplanar waveguide (CPW) line loss at various operating frequency bands is then presented. CPW lines for GaN-on-high-resistivity Si are shown to have a pronounced temperature dependence for temperatures above 150 °C and have lower substrate losses for frequencies above the ${X}$ -band. On the other hand, GaN-on-low-resistivity Si is shown to be more temperature insensitive and has lower substrate losses than even highly resistive Si for lower operating frequencies. The effect of various CPW geometries on substrate loss is also presented to generalize the discussion. These results are expected to act as a benchmark for temperature-dependent substrate loss in GaN-on-Si RF technology. [ABSTRACT FROM AUTHOR]

Thermal discomfort is a driver of negative user experiences with modern VR headsets since they are similar to head-worn gaming computers. Here, we examined the effect of microclimate temperature (MCT; i.e., the air between headset and user) and the effect of standing and seated use on thermal discomfort for a goggle style headset. Users played VR games across three 48-min sessions with different thermal profiles ranging between 28°–43 °C. Perceived thermal and weight discomfort were rated by participants every 12-min. Thermal, but not weight comfort declined during the study period as MCT increased. Users sweat more and had greater forehead temperatures while standing with the lowest thermal profile, suggesting thermal management is more critical for active experiences. Overall, this study recommends MCT should be kept below 36 °C. Finally design for thermal comfort should be tailored to the individual, experience duration and activity level. • Thermal discomfort is an important design factor for VR headsets. • Microclimate temperatures above 36 °C decrease user discomfort. • Lower microclimate temperatures should be a target for active or roomscale experiences. • Headset cleanability is important as increased temperatures drove increased sweating. • Monitoring user skin and microclimate temperature or humidity may help users identify optimal times for rest breaks. [ABSTRACT FROM AUTHOR]

Highlights • Twelve simulations with exothermic reactions & bursting 3-phase interactive jet. • Heat generation lowers droplet sizes. • Changes to flow rates and geometries reveal dynamic spray character shifts. • New measures for energy production sustainability allow optimization tools. • Preferred designs are found by considering different combinations of outcomes. Abstract Past work involving validated "cold-flow" CFD modeling of self-generating and self-sustaining pulsating near-sonic non-Newtonian slurry atomization elucidated acoustic signatures, atomization mechanisms, and the effects of numerics and geometric permutations. The numerical method has now been incorporated with exothermic oxidation reaction kinetics relations along with radiation, i.e. no longer cold-flow. These models provide substantially increased model rigor and allow for new pulsing thermal measures which help assess injector thermal stresses. Twelve models have been run for extended periods of time in order to investigate the effects of dramatic changes in gas feed rate and prefilming (retraction) length. Given the new metrics and models, multiple statistically optimized designs are potentially available depending on the objective function(s) and their relative weightings in the overall value proposition to the project. In the case in which all metrics have equal value to the project and are simultaneously considered in a statistical model, the optimum design involves a mid-level of retraction and a mid-level gas feed rate. If, however, more relative weighting is placed on the importance of droplet size minimization and injector thermal management in lieu of feed passage pressure drop minimization, the optimum design involves a similar retraction but a very high level of gas feed rate. [ABSTRACT FROM AUTHOR]

Highlights • A novel cooling strategy based on the air distribution pipe is proposed for the cylindrical Lithium-ion battery module. • The 3D CFD model of the battery module based on the air distribution pipe is constructed. • The temperature of battery near the positive pole is higher than that near the negative pole during discharging. • The maximum temperature of battery module can be effectively reduced via increasing inlet pressure. • The maximum temperature of battery module declines when the diameter and number of rows for orifice become large. Abstract For a typical air cooling thermal management system, the inlet and outlet of air flow on both sides of the battery module would increase the temperature difference. In here, a novel cooling strategy based on air distribution pipes is proposed for the cylindrical Lithium-ion battery module. The three-dimensional computational fluid dynamics model of battery module is constructed and validated by the experimental tests. The thermal behavior of battery module and the flow field of air have been explored using numerical simulations at different discharge rates, and then the effects of orifice parameters, inlet pressure and discharge rate on the performance of air cooling strategy have been analyzed. The results show that the maximum temperature of the battery module can be effectively reduced by the increase of inlet pressure resulting in a significant rise of power consumption. Meanwhile, it declines when the diameter and number of rows of the orifice increase, following a minor rise in power consumption. When the inlet pressure is 100 Pa, the diameter of the orifice is 1.5 mm, the number of rows of the orifice is 5 and the discharge rate is 3C, the maximum temperature of battery module decreases from 325.9 K to 305.7 K in comparison to that under none air cooling condition. In addition, the maximum temperature difference of battery module is within 3 K. When the battery module discharge at the current rate of 4C and 5C, the maximum temperature of battery module maintains within 313.15 K, but the temperature difference slightly exceeds the optimal range at 5C discharge when the inlet pressure is 200 Pa, the diameter of the orifice is 1.5 mm and the number of rows of the orifice is 5. Moreover, it is an efficient and a practical cooling strategy with no need to modify the arrangement of the battery module. [ABSTRACT FROM AUTHOR]

Highlights • Ultra-high concentrator photovoltaics are promising to low the cost of electricity. • Thermal management is challenging due to the heat produced at ultra-high levels. • The feasibility of flat heat-sinks is studied using a Finite Element Analysis (FEA) • Key parameters for passive cooling within 2000–10,000 suns are investigated. • Results show that the temperature stays below 60 °C for cell areas lower than 1 mm2. Abstract Concentrator photovoltaic (CPV) systems replace semiconductor material by cost-efficient optical elements. The potential cost reduction of these systems is closely related to the concentration factor because higher light concentrations imply lower amount of semiconductor material required for the solar cells. Thus, one promising way for improving this technology is moving towards ultra-high (UH) concentration levels (>2000 suns). However, the thermal management at such extreme light fluxes is difficult. Using small-sized solar cells is beneficial for improving the thermal management. Among the possible cooling strategies, the use of flat-plate heat-sinks for passive cooling, if feasible, would be the simplest way to dissipate the heat and would accelerate the development of UHCPV prototypes. However, the feasibility of flat-plate heat-sinks using microscale solar cells for UHCPV applications has not been analysed in detail yet. In this work, a thermal 3D finite-element model is used to investigate the possibilities of flat-plate heat-sinks at concentration ratios not tested to date, i.e. 2000–10,000 suns. Critical parameters such as solar cell area and efficiency, substrate thickness, heat-sink area, and heat-sink material are evaluated and discussed. Results show that solar cells of 1 mm × 1 mm area or below can be thermally handled with conventional Aluminium flat heat-sinks up to 10,000 suns. [ABSTRACT FROM AUTHOR]

Summary: A thermal management system with the capability of achieving excellent heat dissipation is essential to the development of battery pack for transportation devices. To meet the temperature uniformity requirements of the battery pack, the plate flat heat pipe and liquid‐cooled coupled multistage heat dissipation system had been introduced. In this article, the research status of thermal management systems in battery pack was introduced. And the heat generation and heating power of the Li‐ion cell were studied. Then, the structure model of plate flat heat pipe system was proposed. Finally, the enhanced heat conduction effect of the thermal management system proposed in this article was comprehensively analyzed. Through the analysis of the results, in high discharge rates, the thermal management system proposed in this article could meet the temperature uniformity requirements of battery pack; also, the internal difference would reduce by 30.20%. [ABSTRACT FROM AUTHOR]

Abstract This paper describes a systematic analysis of liquid-phase infiltrated molybdenum (Mo) copper (Cu) composites, deformed by various levels, and elucidates the impact of (i) the copper content, and (ii) the rolling reduction on the evolution of the material properties. The rolling-induced change of the thermo-physical properties can be traced back to (ii-a) the evolution of the geometry (viz. the flattening of the molybdenum and the copper phase during rolling) and (ii-b) the evolution of the crystallographic texture. Four infiltrated ingots with a copper content of 23, 39, 48 and 54 vol % were produced. Each ingot was gradually rolled down to a final degree of deformation of 0.5, 1, 1.5, 2 and 2.38, which corresponds to a rolling reduction of 39%, 63%, 78%, 86% and 90%. In summary, four material compositions (23, 39, 48 and 54 vol % Cu) in six conditions (as-infiltrated and five as-rolled conditions) were examined. The evolution of the microstructure is correlated with the evolution of the mechanical and thermo-physical properties such as hardness (HV2), Young's modulus, E , electrical conductivity, σ , thermal conductivity, k , and the coefficient of thermal expansion, α (CTE, in the range of 350 °C (623 K) – 750 °C (1023 K)). It was found, that the same thermal conductivity can be gained by using either a low copper-content composite that features a low degree of deformation or by using a high copper-content composite that was rolled down to a high degree of deformation. Furthermore, we were able to demonstrate that peculiarities in the CTE-over-T curves can be traced back to the plastic deformation of the copper phase, which is affected by rolling-induced residual stresses and recrystallisation processes during the CTE measurement. Graphical abstract Image 1 Highlights • Four liquid-phase infiltrated MoCu ingots were produced (Cu: 23, 39, 48, 54 vol %). • The ingots were rolled down to five degrees of deformation (0.5, 1, 1.5, 2 and 2.38). • Evolution of the thermal conductivity and expansion behaviour were analysed. • Material properties = f (copper content, degree of deformation (geometry, texture)). • The peculiar expansion behaviour is caused by the plastic deformation of the Cu phase. [ABSTRACT FROM AUTHOR]

Nanocomposite phase change materials (NCPCMs) containing different mass fractions (nanomaterial concentration) and different copper nanoparticle (CN)/multi-walled carbon nanotubes (MWCNT) mass ratios were prepared and experimentally studied. Latent heat and thermal conductivity of the NCPCMs were studied and calculated by using the T-history method. The results revealed that addition of CN or MWCNT to the phase change material (PCM) resulted in NCPCMs with enhanced thermal conductivity and charge rates, respectively. However, when both nanoparticle materials were added to the PCM simultaneously, the resulting NCPCMs improved their thermal performance below expectations as a result of agglomeration and sedimentation between the two additives. Thus, the NCPCMs containing only CN or MWCNT showed superior thermophysical properties than the pure PCM, while the NCPCM containing both CN and MWCNT did not improve the thermal characteristic of PCM significantly. [ABSTRACT FROM AUTHOR]

Abstract Microchannel heat sinks have provided an efficient solution in the thermal management of high-power density devices. In general, however, they cannot exhibit high thermal performance and lower pressure drop simultaneously. In this work, an improved design of microchannel heat sinks possessing a combination of high thermal performance and low pressure drop is proposed, where the superiority of double-layered concept and the advantage of porous-ribs design are taken into account. In the improved design, two layers of rectangular channels are stacked one atop another with porous ribs utilized in the upper layer while solid ribs employed in the lower layer. The thermal performance and the flow characteristics of the improved design are numerically studied using a three-dimensional solid-fluid conjugate model. Four other heat sinks with different structure (solid-ribs single-layered, porous-ribs single-layered, solid-ribs double-layered, and porous-ribs double-layered) are designed for performance comparison. The results demonstrate that the improved design yields the lowest thermal resistance and the best temperature uniformity on the bottom wall among all the five designs whether at an identical Reynolds number or at a fixed pumping power. The appropriate combination of better thermal conductivity of solid ribs and lower pressure drop of porous ribs in a double-layered heat sink is responsible for the performance improvement. Highlights • An improved double-layered microchannel heat sink is proposed. • Porous ribs are employed in the upper layer with solid ribs in the lower layer. • Thermal performance and pumping power both reduce for the improved design. [ABSTRACT FROM AUTHOR]

Abstract The flow dynamics of natural convection during paraffin wax melting is numerically investigated using double-population multi-relaxation-time lattice Boltzmann modeling. Flow dynamics manipulation is achieved using inserts of varying tilt angles θ and positions x *, while the use of insulation material isolates the effects of thermal conductivity enhancement. It is found that improvement in melting duration can reach up to 13%, particularly at low θ and high x * due to restructuring of natural convective currents. Natural convective currents show high potency to enhance melting due to a boost in thermal energy transport and solid-liquid interface progression, especially when the liquid melt phase grows significantly in size. More importantly, the mesoscopic nature of LBM permits natural convective multicellular vortex formation and phase change to naturally manifest themselves, as convective currents rotate in the clockwise direction in multiple degrees of vorticity when melting enhancement occurs. Moreover, the melting process can be expressed in four stages via time-dependent Nusselt number Nu variation. Flow dynamics analysis reveals high natural convective activity, albeit low Nu value even after the four stages of melting process complete early. Overall, the present study may provide new insights into the flow dynamic effects that are underrated knowledge in natural-convective melting, and subsequently would impact the development of available crude oil wax mitigation techniques via thermal management. Highlights • Double population MRT-LBM permits direct modeling of paraffin natural convective melting. • Melting duration of inserts at low θ and high x* outperforms control setup by up to 13%. • Some fascinating features in the flow field are presented to justify hidden changes in natural convection. • Nu profiles observe early ending in four stages of melting process when flow dynamics are enhanced. • More economical thermal management techniques can be developed without complex additive materials. [ABSTRACT FROM AUTHOR]

Abstract In this review, the operation and functionality of batteries used in industrial applications will be investigated. It will be discussed how and why batteries degrade and lose efficiency because of improper thermal management and based on that it will be explained what methods and techniques can be applied to reduce this impact. Through this, it will be explained how heat management methods could be used to thermally control batteries. In addition to this, it will be indicated what technologies can be employed to manage thermal boundaries of batteries. A comprehensive review of the current state of the art technologies currently used will be followed by that which will include how these technologies can be applied as thermal management systems for batteries. [ABSTRACT FROM AUTHOR]

This paper demonstrates an experimental micro- channel solution to cool microelectronic chips with hotspots, using an integrated, yet nonintrusive technique. In microelectronics, approaches such as die thinning induce acute stress on cooling because it increases the hotspot phenomena and reduces chip bulk thickness that could be used for microchannels. In compact devices, heat must be removed using limited pumping power and cooling space. Microchannels etched in the backside of the chip, usually considered as an efficient cooling solution, are impracticable on highly thinned chips. This paper experimentally investigates the cooling performance of a noninvasive and hotspot aware microchannel die that is in direct fluidic contact with the backside of the microelectronic chip. It also proposes a confinement-wise metric. A thermal resistance of 2.8 °C/W is achieved at a heat flux of 812 W/cm2 per heat source, for a total dissipated power of 20 W and a maximum allowed temperature rise of 55 °C. Such performance is obtained with only 19.2 kPa of pressure drop and 9.4 ml/min of flow rate, corresponding to a hydraulic power of only 3 mW and a coefficient of performance of 6500. In addition, the complete chip stack, including the thinned chip, measures only $660~\mu \text{m}$ high. Therefore, backside cooling appears to be a promising compact and low consumption solution for compact electronic applications having confined hotspots. [ABSTRACT FROM AUTHOR]

Abstract Effective thermal management systems, designed to handle the impacts of thermal runaway (TR) and to prevent cell-to-cell propagation, are key to safe operation of lithium-ion (Li-ion) battery assemblies. Critical factors for optimizing these systems include the total energy released during a single cell TR event and the fraction of the total energy that is released through the cell casing versus through the ejecta material. A unique fractional thermal runaway calorimeter (FTRC), designed to characterize said critical factors, was utilized to examine the TR behavior of 18650-format Li-ion cells representing a variety of manufacturers, chemistries, capacities, and safety features. Primarily, the impacts of bottom vent (BV) safety features, varied cell casing thickness, and Dreamweaver cellulose based separators were assessed for select cell types. A subset of cells also had an imbedded internal short circuiting (ISC) device to allow examination of TR behavior initiated at lower temperatures (i.e. closer to field failure conditions). The impact of bottom rupture on TR behavior was also examined for experiments that resulted in this non-standard failure mechanism. Statistical analysis of the results for each cell configuration reveals that a lognormal distribution effectively characterizes the variation of total TR energy release. Typically 20%–30% of the total energy yield is released through the cell casing with the remainder through the ejecta material. Higher energy cells tend to exhibit more violent ejections and less predictable TR events. Inclusion of a BV feature reduces the overall severity of the TR event and can increase the predictability. Results also suggest that the magnitude of the TR event may not be directly proportional to the stored electrical energy, but rather has additional dependence on other design and failure mode factors. Highlights • Li-ion cell thermal runaway characterized with fractional calorimetry techniques. • Results distinguish between energy released through cell casing vs. ejecta material. • Impacts of design variables on thermal runaway behavior are characterized. • Statistical analysis reveals the variability of total thermal runaway energy release. [ABSTRACT FROM AUTHOR]

Heat generation and accumulation during working schemes of the lithium-ion battery (LIB) are the critical safety issues in hybrid electric vehicles or electric vehicles. Appropriate battery thermal management is necessary for ensuring the safety and continuous power supply of rechargeable LIB modules. In this study, thirty cylinder 18650-type cells were fabricated a 6S5P battery module with a 2-mm spacing between cells to evaluate exothermic trajectories. The modules, equipped with a forced-air cooling system, were charged at 1 C-rate and discharged at 1, 1.5, and 2 C-rates for three cycles in each test; thermocouples were connected to the cells to track the variances in temperature and voltage. The efficiency of the developed forced-air cooling system was estimated to be 73.0% in case 1 with the 1 C discharge rate, and the temperature difference (TD) was less than 5.0 °C. The maximum temperature (Tmax) of this case was maintained below 45.0 °C showing uniform heat distribution. Moreover, extreme heat accumulation developed inside the module and damaged the adjacent LIBs during fast 2 C discharge test. Our TD testing showed that a forced-air cooling system in the LIB module provides effective heat dispersion under normal discharge conditions. [ABSTRACT FROM AUTHOR]

An ever-growing market demand for board (second) level packages (e.g., embedded systems, system-on-a-chip, etc.) poses newer challenges for its manufacturing industry in terms of competitive pricing, higher reliability, and overall dimensions. Such packages are encapsulated for various reasons including thermal management, protection from environmental conditions and dust particles, and enhancing the mechanical stability. In the due course of reducing overall sizes and material saving, an encapsulation as thin as possible imposes its own significance. Such a thin-walled conformal encapsulation serves as an added advantage by reducing the thermo-mechanical stresses occurring due to thermal-cyclic loading, compared to block-sized or thicker encapsulations. This paper assesses the encapsulation process of a board-level package by means of thermoset injection molding. Various aspects reviewed in this paper include the conception of a demonstrator, investigation of the flow simulation of the injection molding process, execution of molding trials with different encapsulation thicknesses, and characterization of the packages. The process shows a high dependence on the substrate properties, injection molding process parameters, device mounting tolerances, and device geometry tolerances. Nevertheless, the thermoset injection molding process is suitable for the encapsulation of board-level packages limiting itself only with respect to the thickness of the encapsulation material, which depends on other external aforementioned factors. [ABSTRACT FROM AUTHOR]

The environmental and sustainability issues related to fossil fuel have made electric vehicles an alternative solution with lithium ion (Li-Ion) as the energy source. The sensitive nature of Li-Ion batteries has led to an active research on their thermal management for the past decade. The rise in temperature in Li-Ion batteries involves complex dynamics and there are several approaches to control it. Keeping it as the focus of research, this paper illustrates the application of design of experiments (DOE) to optimize the control variables involved in thermal management. Control variables used for optimization are mass of phase change material (PCM), thermal conductivity of paraffin copper composite (PCC) and water flow rate (WFL). The influence of these variables on the temperature rise of Li-Ion batteries has been studied. The research methodology involved full factorial DOE with two replications to analyze the influence of temperature control parameters of Li-Ion batteries. Multivariate analysis involved analysis of variance (ANOVA) that was used to test the hypotheses, which included the first and second-order interaction effect of control variables. The hypothesis testing has revealed that all the variables of study had a significant influence on the temperature rise of the Li-Ion batteries. The outcome of this research will be useful for Li-Ion battery manufacturers, as it provides suggestions to design appropriate cooling systems for the battery pack. [ABSTRACT FROM AUTHOR]

Highlights • A novel elliptic capsule is suggested for the large scale latent thermal energy storage. • Motion of PCM lump in elliptic capsule is reported which improved the heat transfer rate. • Elliptical capsule decreases the charging/discharging time by 50% and 35%, respectively. • Test for 1000 L of water reveals charging/discharging time of 4.8 and 6.25 h, respectively. Abstract A latent heat thermal energy storage (LHTES) system is an efficient thermal battery using a phase change material (PCM) for key applications of intermittent renewable energy. In this study, a flexible elliptical-shaped capsule is investigated and subsequently proposed as a container of the PCM used for LHTES. The novel elliptical PCM capsule is made of polyethylene and designed to achieve maximum enhancement of heat transfer. The thermal flow inside the capsule is analyzed via the combined methods of particle image velocimetry and laser induced fluorescence. In the present study, the upward and downward motion of a solid PCM lump in an elliptical capsule are reported for the first time. This is shown to increase the heat transfer rate by more than twice that of a spherical capsule. A prototype heat storage tank with 1000 L of water and 500 kg of the PCM is fabricated for application as a large-scale thermal battery. Consequently, the developed PCM capsule exhibits a decrease of 50% and 35% in the charging and discharging process time, respectively. [ABSTRACT FROM AUTHOR]

Highlights • A method for thermal management of battery using phase change material is proposed. • Temperature of battery is rapidly decreased using flexible phase change material. • Flexible phase change material fills the gap due to low thermal contact resistance. • The usage time of the battery pack is effectively extended. • Simulation results show good agreement with experimental results. Abstract A method for thermal management of Li-ion battery pack with the application of various flexible form-stable composite phase change materials (CPCMs) is proposed, and investigated both numerically and experimentally. Flexible CPCMs embedded in battery pack lower the thermal contact resistance, thereby improving the thermal control performance. Experimental results show that with the application of flexible CPCMs, the battery temperature drops by 18 °C at 10 C discharge rate. In addition, flexible CPCM has better thermal control performance than the case of conventional CPCMs. This allows Li-ion battery pack to safely work for an extended period of time without exceeding upper temperature limits. The thermal control performance is observed to vary considerably with three factors: the phase change temperature of flexible CPCMs, working condition, and the ambient temperature. One flexible CPCM with phase change temperature of 33 °C is found to be optimal for small power levels and low ambient temperatures. Another flexible CPCM with 47 °C of phase change temperature is suitable for high power levels, short-term high heat fluxes, and high ambient temperatures. The numerical results are in reasonable accordance with experimental ones. [ABSTRACT FROM AUTHOR]

Highlights • The effects of temperature on the performance of batteries were performed. • Battery modeling methods and thermal management strategies were discussed. • A systematic review of liquid based thermal management system was presented. • An integrated system with suitable energy allocation and control unit is desirable. Abstract Electric vehicles with green power system are viable alternatives to reduce greenhouse gas emissions and dependence on fossil energy resources. The power source such as Li-ion battery has high sensitivity to temperature, which is a challenge related to battery thermal management. Battery thermal management system plays a vital role in the high efficiency, dependability and security of these batteries. Modern commercial electric vehicles normally use liquid based battery thermal management system, which has high heat transfer efficiency with the function of cooling or heating. This paper firstly looks at the effects of temperature on the battery performance from three aspects: low temperature, high temperature and differential temperature. Then the battery management system is discussed with the main emphasis on battery modeling methods and thermal management strategies. Further, a systematic review of liquid based system is presented in terms of direct and indirect contact mode. Progress made in liquid channel configuration and heat transfer fluid aiming at improving the overall thermal performance is also discussed. With the function of liquid-gas phase change process, the heat pipe based battery thermal management is feasible and effective for its high heat transfer efficiency. To further facilitate vehicle-mounted energy optimization, an integrated vehicle thermal management system with appropriate energy allocation is required. In addition, the battery thermal management system connected with the other subsystems (e.g., heating ventilation air conditioning system) by utilizing the liquid circulation in vehicle thermal management has great potential in energy-saving and efficiency promotion. [ABSTRACT FROM AUTHOR]

Graphical abstract The multilayered ACPCs based on PP/MWCNTs composites were prepared with outstanding conductive anisotropy, excellent current-carrying capability and directional heat dissipation, demonstrating the applications for electrical and thermal management. Highlights • Multilayered composites were fabricated via a facile but environmental friendly way. • Such composites show remarkable anisotropic electrical and thermal conductivity. • Such composites exhibit strong interfacial strength and enhanced thermal stability. • Such composites can be easily processed into desired macroscopic shapes. • This approach can be easily scaled up for industrial production. Abstract Multilayered objects are some of the most common composites in nature with outstanding performance that cannot be achieved by a single component. To expand the application of multilayered composites with excellent anisotropic properties, facile and environmental friendly fabrication methods and low-cost raw materials are unambiguously required. The Chinese traditional food called "thousand-layer pie" is an example of such composites with multilayered structure, showing visual attractiveness and having delicious taste. Borrowing the idea from the method of preparing this food, anisotropic conductive polymer composites (ACPCs) with alternating microlayers of pure polypropylene (PP) and PP filled multi-walled carbon nanotubes (PPCNTs) were prepared by a combined polymer melt processing technique. The multilayered structure endowed the ACPCs with inner layer conduction but interlayer insulation. The electrical conductivity in X direction reached up to 1 S/m and exhibited a value almost 16 orders of magnitude higher than the value in Z direction, which was by far the most remarkable conductive anisotropy compared with the reported counterparts. The anisotropic functionality of the ACPCs enabled them to be used in electrical and thermal management applications, such as subminiature integrated circuits, highly reliable electrical interconnects and anisotropic thermal conduction. Considering the low-cost raw materials used and the facile preparation process, this approach can be scaled up for industrial production, promoting such ACPCs with high performance and functionality to be implemented in a variety of applications. [ABSTRACT FROM AUTHOR]

Electric vehicles (EVs) powered by lithium batteries, which are a promising type of green transportation, have attracted much attention in recent years. In this study, a thermoelectric generator (TEG) coupled with forced convection (F-C) was designed as an effective and feasible cooling system for a battery thermal management system. A comparison of natural convection cooling, F-C cooling, and TEG cooling reveals that the TEG is the best cooling system. Specifically, this system can decrease the temperature by 16.44% at the discharge rate of 3C. The coupled TEG and F-C cooling system can significantly control temperature at a relatively high discharge rate. This system not only can decrease the temperature of the battery module promptly but also can reduce the energy consumption compared with the two other TEG-based cooling systems. These results are expected to supply an effective basis of the design and optimization of battery thermal management systems to improve the reliability and safety performance of EVs. [ABSTRACT FROM AUTHOR]

Abstract Thermal management technology based on the magnetocaloric effect offers several advantages over conventional gas compression cooling. The efficiency of magnetic cooling systems can be much higher than conventional gas based cooling technologies. Additionally, ozone layer depleting chemicals are not used and there is reduced noise and vibrations. Iron and manganese based magnetocaloric materials (MCM) are promising due to the challenges surrounding the use of conventional rare earth based MCM. We review the recent progress in the development of iron and manganese based MCM. The magnetic phase transitions, processing techniques, performance, as well as applications of these materials are discussed. Critical analysis to determine the critical exponents and phase transition behavior of these MCM, using modified Arrot plot, critical isotherm plots, the Kouvel-Fisher method, Landau theory and the Bean-Rodbell model, is also presented. [ABSTRACT FROM AUTHOR]

Since the early days of computing, excess heat has been a major road block in the design and development of faster, more efficient, and more compact electronic devices. Coupled with improvements in thermal management has been a reduction in the size of major electronic components, primarily transistors. This has expanded the field of thermal management down into the nanoscale, where the "rules" of thermal transport become more complicated. This paper presents a brief perspective on the historical challenges in thermal management and outlines the major length scale regimes where thermal management is being developed. In particular, the expansion of thermal management into the nanoscale is presented due to the consequence that as the feature size of most nano-devices continues to diminish, the impact of thermal transport across solid-solid interfaces on device performance, reliability, and lifetime becomes increasingly important. [ABSTRACT FROM AUTHOR]

Highlights • Optimization of in-line cylindrical pin-fin heat sinks is carried out. • Constructal theory and thermo-economic theory are applied. • Total operation cost based on entropy generation is taken as objective. • Optimal constructs of cylindrical pin-fin are obtained. Abstract Second-law-based minimum operation cost optimization is performed based on constructal theory for in-line cylindrical pin-fin heat sinks (PFHS). With the minimum operation cost which is based on the entropy generation rate (EGR) as the objective, the optimal values of diameter, height to diameter aspect ratio and quantity of cylindrical pin-fin are achieved by combining the analytical and numerical method, the effects of fin-material fraction (FMF), heat transfer load (HTL) of the PFHS, fluid velocity (FV) and cost ratio on variations of the operation cost of the PFHS with the diameter of pin-fin are analyzed. The results indicate that when the single freedom degree optimization is performed, the minimum operation cost and the optimum constructs are various under various FMF, the HTL, the FV and the cost ratio in the research range of parameters; when the double freedom degree optimization is carried out, the operation cost of the PFHS increases with the height to width aspect ratio of the PFHS increasing. [ABSTRACT FROM AUTHOR]

The ever-increasing demand for high-processing compact electronic systems has unequivocally called for improved microprocessor performance. However, increasing microprocessor performance requires increasing power and on-chip power density, both of which are associated with increased heat dissipation. Electronic cooling using fin has been identified as a reliable cooling approach in miniaturized electronic systems. However, an investigation into the thermal behavior of fin would help in the design of miniaturized, effective heatsinks for reliable microprocessor cooling. The aim of this paper is to investigate the simultaneous effects of surface roughness, porosity, and magnetic field on the performance of a porous microfin under a convective–radiative heat transfer mechanism. The developed thermal model considers variable thermal properties according to linear, exponential, and power laws, and is solved using the Chebychev spectral collocation method. A parametric study is carried out using the numerical solutions to establish the influences of porosity, surface roughness, and the magnetic field on the microfin thermal behavior. The results of the simulation establish that thermal efficiency of the microfin is significantly affected by the porosity, magnetic field, geometric ratio, nonlinear thermal conductivity parameter, thermogeometric parameter, and the surface roughness of the microfin. Furthermore, the study establishes that the fin efficiency ratio which is the ratio of efficiency of the rough fin to the efficiency of the smooth fin is found to be greater than unity when the rough and smooth fins of equal geometrical, physical, thermal, and material properties are subjected to the same operating condition. [ABSTRACT FROM AUTHOR]

With current trends toward increased power in smaller devices and packages, the search continues for high-performance thermal management solutions for MOSFETs, high-electron mobility transistors, and other power electronics. Microjet impingement cooling has been shown to produce high heat transfer capabilities for electronics cooling. In this paper, microjets based on well-studied geometries were embedded within the substrate of a heat-producing device, removing several layers of thermal resistance typically found in advanced packages. In contrast with competing liquid cooling solutions that use expensive materials and processes, industry-standard silicon microfabrication techniques were used to build a low-cost microjet cooler. Numerical analysis of the embedded microjet device showed average heat transfer coefficients greater than 250 kW/ $\text {m}^{2}\cdot \text {K}$ and low peak temperature rises in high power-density devices. Using an innovative micro-Raman thermography technique, experimental measurements with a 1- $\mu \text{m}$ spatial resolution were taken, supporting the numerically predicted heat transfer coefficients on a device with a heat flux of over 5 kW/cm2 and a temperature rise of 46 °C. As devices continue to become miniaturized, both low-cost embedded microjet cooling technology and micro-Raman thermography may play a vital role in the design, operation, and evaluation of advanced high power-density electronics. [ABSTRACT FROM AUTHOR]

The ability of packaging solutions to meet the high heat flux dissipation of power electronics relies heavily on effective thermal management strategies. During operation, power electronic devices generate high temperatures that can cause device degradation. To remove this heat from the devices, heat spreaders and cold plates are often used. However, the multiple layers that compose the module often lead to high thermal resistances that hinder heat dissipation and can give rise to interfacial failures. To address these challenges, this paper has investigated the direct integration of single-phase jet impingement cooling at the power electronic substrate level for improved thermal management. This method was evaluated using computational models, experiments, and analytical models. An optimization analysis was performed to determine the influence of various design parameters on the cooling system. Through the directly integrated cooling concept, a reduction of up to 25% in the total package thermal resistance compared to a conventional device package was achieved. In addition, the overall device temperature was reduced, and the thermal resistance was found to be between 0.21 °C/W and 0.47 °C/W for a heat dissipation of 100 W/cm2. [ABSTRACT FROM AUTHOR]