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An industrial integrated energy system gathers a variety of production capacity and energy-related units, which also involves the production, transformation, and consumption of cold, heat, power, gas, etc. The combined cooling, heating, and power (CCHP) system built upon the cascade utilization of energy plays a significant role in improving the utilization rate of multiple energy resources. In this article, a controlled hierarchical relevance vector machine is modeled for identifying the scheduling event in the by-product gas system of a steel industry, which can effectively overcome the disturbance triggered by the changing of operational modes (OMs). Considering the multiple time scales (MTSs) property and the changing of seasons and load conditions of the CCHP, a unified modeling approach is proposed to describe MTSs and multiple OMs of the CCHP by using fuzzy singular perturbation here. Furthermore, an extended $Q$ -learning approach by incorporating a hierarchical interval type-2 fuzzy system is designed for dynamically choosing the optimal controller’s parameter for the proposed unified model along with the changing of OMs. The performance of the proposed method can be experimentally validated by a series of industrial application cases to highlight the necessity of modeling and self-adaptive parameter of the controller. [ABSTRACT FROM AUTHOR]

Electric vehicles (EVs) are booming all over the world for a low carbon emission and greener environment. The fast charging is an urgent demand for consumers. However, the dramatic temperature rising during high-power charging has a high risk of trigging thermal runaway and other safety issues. This article proposes an external liquid cooling method for lithium-ion battery module with cooling plates and circulating cool equipment. A comprehensive experiment study is carried out on a battery module with up to 4C fast charging, the results show that the three-side cooling plates layout with low coolant temperature provides better temperature control effect, while the coolant velocity and type have very weak impact. Then the simulation model with high precision is built for ultra-fast charging, and a safe charging range under 5C charging is proposed. The safe charging range under 5C can be increased by 50.1%. The environment close to the room temperature demonstrates the best effects of external cooling. For actual applications in the EVs, the circulating cooling equipment outside EVs can be integrated with high-power charging infrastructure and provide a 117 km improvement in mileage under 5C safe charging which indicates a tremendous application prospect. [ABSTRACT FROM AUTHOR]

A novel winding embedded liquid cooling (WELC) concept is presented to improve the thermal management of slotless motors for transportation applications. The concept introduces liquid cooling channels through the non-magnetic thermal plastic winding support in a slotless motor to reduce the thermal resistance between the heat source and the sink. This article demonstrates the efficacy of the WELC concept for a 11.5-kW slotless motor using computational fluid dynamics (CFD). A lumped parameter thermal network has also been developed for the WELC concept, which has been validated using the CFD analysis. The simulation results of WELC concept have been experimentally validated for an 11.5-kW slotless motor. It is shown that the WELC concept can achieve a continuous current density of 19.0 A(rms)/mm $^{2}$ for an allowable temperature rise of 80 $^{\circ }$ C; the achieved continuous current density is 35% higher than that of a conventional axial in-slot water jacket cooling. The short time (18 s) peak current density achieved with the WELC concept is 39.8 A(rms)/mm $^{2}$. [ABSTRACT FROM AUTHOR]

The boom of fluctuating renewable energies puts forward higher requirements on reserve capacity for maintaining the power system balance. To address this issue, this letter investigates a novel distributed event-triggered consensus control (ETCC) method of large-scale inverter air conditioners (IACs) for demand response, which can achieve the same regulation objective and response speed while significantly relieving the communication burden compared with traditional time-scheduled consensus control methods. Based on Lyapunov stability theorem, we also prove the convergence of the ETCC with nonlinear protocol for massive IACs. Finally, the above models and methods are verified by numerical studies. [ABSTRACT FROM AUTHOR]

This article proposes a computationally efficient thermal study method that substitutes computational fluid dynamics (CFDs) with a finite-element analysis (FEA) involving minimal loss of accuracy and omission of the increased computational load. The suggested technique contributes toward the realization of multiphysics optimization of high-speed electrical machines that effectively includes critical thermal evacuation phenomena. The strategy is regression-based and succeeds in constructing convection coefficient regression models that typically involve many variables and small training datasets. The proposed scheme is verified in high-loss density and high-speed outer rotor surface-mounted permanent magnet (SMPM) motor geometries that an optimization algorithm typically encounters during execution. The reference target specifications correspond to 20 kW output power, 15k r/min rotating speed, and 2 kHz electrical frequency. [ABSTRACT FROM AUTHOR]

This article presents the design and analysis of a double-side-cooled printed circuit board (PCB) embedded silicon carbide (SiC) MOSFET half-bridge package with low loop inductances and an integrated gate driver. The 1.2 kV SiC MOSFET dies used in the half-bridge package are embedded in the PCB using AT&S's patented technique. The dies are cooled and electrically connected to traces in the PCB through copper-filled microvias. The design methodology accounts for both electrical and thermal performance, limiting the power-loop inductance to 2.3 nH and the maximum package temperature to less than the 175 °C limit. The integration of the gate drive circuitry allows for a high power density and 2.2 nH gate-loop inductances. At 0.12 K/W, the measured junction-to-case thermal resistance with double-sided cooling is 57% lower than that of a TO-247 package. Under similar operating conditions, the PCB-embedded half-bridge package also achieves a 5.6 times lower voltage overshoot and a 0.5% higher peak efficiency than a TO-247-based half-bridge. This article reports the first demonstration of PCB-embedded 1.2 kV SiC MOSFET packages in buck, boost, and ac–dc converters. The prototype three-phase ac–dc converter for an electric vehicle on-board charger is composed of six PCB-embedded half-bridge packages and achieves an efficiency of 98.2% and a power density of 182 W/in3. [ABSTRACT FROM AUTHOR]

This article describes the design and performance of a dielectric fluid cooling concept for automotive power electronics. The concept combines a low-thermal-resistance package (which eliminates metalized ceramic substrates) with a high-performance convective cooling strategy (slot jets impinging on finned surfaces). Modeling was first used to design the cooling system to maximize thermal performance and minimize pumping power. A prototype was then fabricated, and experiments were conducted to validate the model predictions using three fluids at various fluid flow rates (16.7 cm3/s [1 L/min] to 68.3 cm3/s [4.1 L/min]) and inlet temperatures (30 °C and 70 °C). The final design was compact (120-cm3 total volume, including heat exchanger and conceptual power modules) and cooled 12 devices (e.g., silicon carbide [SiC]). The validated model was then used to predict the junction-to-fluid thermal resistance and pumping power for various conditions, including −40 °C fluid temperature. The results predict thermal resistance values as low as 19 mm2·K/W is possible using the dielectric fluid cooling approach. The dielectric fluid cooling system is predicted to provide thermal resistance and pumping power values that are approximately 56% and 90% lower, respectively, compared to an automotive power electronics cooling system. Moreover, the dielectric fluids can be used for direct cooling of the bus bars, which can be an effective capacitor and gate driver cooling strategy and enable the use of new driveline fluids tailored for this application. [ABSTRACT FROM AUTHOR]

Conventional thermal flow sensors require samples to be heated; however, the temperature rise of the measuring tools limits their use in biological applications. To address this limitation, in this study, we propose a thermal flow sensor with a bidirectional thermal reference. We fabricated an integrated calorimetric and hot-film thermal flow sensor with a bidirectional thermal reference using a Peltier module to produce a thermal distribution that depends on the flow rate. The integrated thermal flow sensors enable high-resolution and wide-range flow rate measurements in a microfluidic device without the use of heating reagents in the cooling measurement mode. In addition, the sensor can be used as a typical heating thermal flow sensor by inverting the current applied to the Peltier module. Computational fluid dynamics simulations and experiments were performed to evaluate the performance of the integrated sensors in heating and cooling modes. In both modes, the calorimetric sensor measured low flow rates with a resolution of 100 nL/min, whereas the hot-film sensor measured a wide range of flow rates up to 200 $\mu \text{L}$ /min. The proposed sensor expands the use of the thermal flow sensors by switching between the cooling and heating modes according to the sample temperature and maximum temperature limit. [2022-0090] [ABSTRACT FROM AUTHOR]

Power transformers are critical assets for generation and grid. Controlling their aging is an essential task to ensure the availability of installations, and to optimize maintenance and operational costs over their lifetime. Large power transformers do not always operate at their full cooling capacity, and the cooling efficiency is often adjusted by steps (each different step being also called a “cooling stage”) based on the top-oil, winding temperature indicator or hot-spot temperature. Various dynamic thermal models exist in the literature, but none of them provide easy-to-use correction factors to consider the effect of the cooling stage on the coolers’ thermal resistance as well as on top-oil and hot-spot gradients. The purpose of this article is to propose a simple yet accurate model for the thermal monitoring of Oil Directed Air Forced power transformers. Several applications of the model are given such as cooling efficiency monitoring, evaluation of the load capability (or loadability), and coolers temperature control improvement. [ABSTRACT FROM AUTHOR]

The chips present unsteady and highly concentrated heat fluxes and the available volume for cooling solution is significantly constrained with the trend of miniaturization and integration. Traditional liquid cooling techniques fail to regulate the coolant distribution according to the changing thermal environment and remove the unevenly distributed thermal loads effectively. In this article, embedded cooling with self-adaptive microchannel/pin-fin hybrid heat sink is proposed. Hybrid channels with thermal-sensitive hydrogels at the outlet are designed and integrated into the substrate. A numerical model is established and an iteration procedure is designed to investigate the flow regulation behavior. The hydrogel downstream of the hotspot undergoes volume reduction and the local coolant flow rate is enlarged, illustrating the autonomous flow regulation effect. Various nonuniform heat load distributions are considered. Taking advantage of the current self-adaptive cooling solution, heat flux of up to 500 W/cm2 can be dissipated and the peak temperature is reduced by 12.2 K with a pressure drop of 34.0 kPa. The embedded self-adaptive cooling provides both effective and intelligent thermal management for densely integrated electronics. [ABSTRACT FROM AUTHOR]

The rotor cooling poses a significant challenge for high-speed permanent magnet synchronous machines. This article presents a recirculating hollow-shaft oil cooling structure. Through the computational fluid dynamics (CFD) method, its convective heat transfer characteristics are studied in depth. Besides, the recirculating hollow-shaft cooling (RHSC) is compared with the direct-through hollow-shaft cooling (DHSC). Based on the CFD analysis, it is found that the convective heat transfer coefficient (CHTC) of the RHSC is higher than that of the DHSC, which can be as high as 58%. Furthermore, the advantage of the RHSC is most prominent at low rotational speed and small flow rate due to its relatively large oil friction loss at a high rotational speed. Moreover, the explanation for the fluctuation of the CHTC before the critical rotational speed, as well as the law of its variation with rotational speed and flow rate, are revealed in this study. The correctness of the simulation analysis is verified by experiments implemented on a rotor setup. In order to summarize the convective heat transfer law of the RHSC better, a dimensionless empirical equation is fitted finally. [ABSTRACT FROM AUTHOR]

This article presents a cost-effective thermal characterization approach that relies on temperature measurements and numerical simulations to solve an inverse heat transfer (IHT) problem for the in situ estimation of thermophysical properties of high-frequency magnetic components. This approach is applied to the magnetic components of a commercial electric vehicle dc fast charger, specifically, to an air-cooled inductor-transformer assembly. Numerical simulations solve a conjugate conduction–convection IHT problem based on surface temperature measurements collected during realistic operating conditions of the charger. These simulations enable rapid in situ estimation of the specific heat capacities, thermal conductivities, volumetric heat generation rates, and convective heat transfer coefficients of the cores and windings of these magnetic components. These estimated properties are then used as inputs in a direct heat transfer (DHT) simulation for the thermal analysis of these components under different cooling conditions, namely natural and forced convection. The thermal analysis of the inductor-transformer assembly shows that active air cooling with forced convection allows sustaining the measured charging power (28.8 kW) up to 6630 s when the surface temperatures of the cores reach the 100 $^{\circ }$ C threshold. This charging time is 61.7% longer than that allowed by the passive air cooling at the same charging power. [ABSTRACT FROM AUTHOR]

An optimized concept of the Cold-Electron Bolometer (CEB) with Superconductor-Insulator-Normal (SIN) Tunnel Junction and Andreev SN contact for voltage-bias mode has been developed. The responsivity of this design is much better than the widespread concept of the CEB with two SIN tunnel junctions for the current-biased mode (SINIS structure) due to degradation of responsivity by a factor of two in voltage-bias (VB) mode. Besides that, for the realization of the CEB with the same capacitance, we need twice larger junctions that lead to four times larger area and volume of the absorber. As a result, the NEP of one SIN junction CEB is half that of two SIN junction CEB. A novel concept of the quasiparticle cascade amplifier (QCA) based on harvesting the waste energy of relaxed quasiparticles without any additional voltage bias has been developed. The distinguish feature of the cascade principle is utilizing the same dc voltage as used for CEB. The cascade principle of signal amplification proved to be possible due to the conversion of electrons to holes in the second absorber. The amplifier is based on the optimized CEB with one SIN junction and one SN contact. The coefficient of power amplification of the incoming signal to the potential energy of hot quasiparticles is huge and can achieve a level of 140 at the optimal bias point. The coefficient of power amplification of the QCA can reach a value of 30 and more to overcome the noise of the SQUID amplifier. For a power load of 6 pW, the total NEP of the CEB is decreased to the level of photon noise NEP, down to 0.7*NEPphot. [ABSTRACT FROM AUTHOR]

Steadily increasing rated unit power of direct-drive wind turbine generators for offshore applications requires solutions with high torque density. HTS excitation windings allow for a higher electromagnetic utilisation compared to an excitation by rare-earth permanent magnets but must be competitive regarding overall cost. This work addresses this multi-objective optimisation problem (mass, cost) by means of a numerical evaluation for a generator design with conventional iron parts and HTS excitation winding under variation of eight variables. The Pareto frontier is approximated for HTS excited direct-drive generators in the 7 MW power class. [ABSTRACT FROM AUTHOR]

The entropy changes in successive martensitic phase transformations in Ni-Mn-Ga Heusler alloys can be used to realize enhanced magnetocaloric properties. A detailed study of phase transformations of one such alloy, Ni2.15Mn0.85Ga ($\Delta Q =4900$ J/kg at 343 K, under 140 kOe), is reported here. Upon cooling, the paramagnetic cubic (L21) austenitic phase transforms into a ferromagnetic 7M modulated monoclinic martensitic phase. This phase is stable in a narrow temperature range, and upon further cooling, it transforms into a non-modulated ferromagnetic tetragonal (L10) phase. The separation between the equilibrium temperatures of the austenitic and tetragonal martensitic phases is only ~50 K. The alloy undergoes reversible temperature-induced martensitic and inter-martensitic phase transformations with thermal hysteresis of about 25 K. The conclusions from the detailed study of the phase transformations lead to new possibilities to enhance the magnetocaloric effect (MCE) using the entropy associated with multi-structural transformations. [ABSTRACT FROM AUTHOR]

In this article, we propose an embedded cooling structure with thermal transmission line (ECS-TTL) to improve thermal integrity (TI) and signal integrity (SI) of a high-bandwidth memory (HBM) module. The proposed hierarchical cooling scheme, ECS-TTL, consists of ECS for lowering thermal resistance and TTL for smoothing thermal distribution. The ECS cools the module’s integrated circuits by circulating fluid inside the computing module components. The TTL is a novel interconnection that focuses on transferring internal heat in a horizontal direction to achieve a uniform thermal distribution. The low and uniform thermal distribution achieved by the ECS-TTL can improve the temperature-dependent SI of an HBM module. We designed ECS-TTL by considering the structural reliability and SI of the HBM module based on its physical dimensions. We conducted TI verification of the HBM module by using a 3-D computational fluid dynamics solver; we evaluated the maximum temperature and the temperature uniformity of the HBM module with the proposed ECS-TTL and other cooling structures. Based on the TI evaluation, we conducted SI verification of the HBM by using a 3-D electromagnetic solver considering the operating thermal distribution; we evaluated the eye diagram and skew of the silicon interposer, through silicon via channels and a 3-D clock distribution network in the HBM. The evaluation verified that the proposed ECS-TTL can achieve a low and uniform thermal distribution while improving the eye diagram and skew of the HBM module compared to the conventional cooling structure. [ABSTRACT FROM AUTHOR]

The electric drive power density and fault tolerance capability are of fundamental importance in many applications such as aerospace and traction applications. The modularization and the physical integration of the electric motor and the power converter components can lead to a high power density and a high fault tolerance drive system. The power density of a highly modular and integrated drive based on an axial flux permanent magnet synchronous machine and GaN converter is investigated in this paper. Several power density boosting techniques are provided and investigated using CFD simulations. These techniques incorporate optimization of the converter topology, the geometry of the shared cooling structure of the electric machine and the power converter and optimal selection of the materials in the path of heat transfer from the machine and the power converter to the cooling ambient. The power density of the reference integrated design is increased from 1.12 kW/ $l$ to 2.14 kW/ $l$. The CFD computations are validated by extensive measurements on a modular integrated setup. [ABSTRACT FROM AUTHOR]

This article presents the comparison of the dielectric properties of three different refrigerant fluids, HFE-7100, HFC-245fa, and HFO-1336mzz(E) (R-1336E Opteon ME), the latter having a global warming potential of two orders of magnitude lower than the other two. Refrigerant fluids are used, among others, in generator circuit breaker applications where good thermal and chemical properties must be coupled with excellent dielectric strength and low electric conductivity. This article describes in detail the applied measurement techniques and the results obtained, as well as comparisons to previous measurements and literature. The comparison includes dielectric breakdown in liquid and vapor phase, dc conductivity, real permittivity, and dissipation factor. [ABSTRACT FROM AUTHOR]

We establish a conceptual model of the graphene-assisted near-field electroluminescent refrigerator (GANER), which is composed of an emitter and a receiver. The two basic components are formed by a homojunction structure using III–V group semiconductors as materials. The cooling rate density (CRD) and coefficient of performance (COP) of the GANER are derived based on fluctuation electrodynamics and thermodynamics. The electrical–optical–thermal coupling properties and parametric optimum designs of the GANER and the near-field electroluminescent refrigerator (NER) are studied. The performances of the GANER and the NER are compared. By making tradeoff between the CRD and the COP, the selective criteria of several key parameters are provided. The effects of graphene’s chemical potential and finite-rate heat transfer between the refrigerator and the environment on the optimum performances of the GANER are discussed. It is found that for an arbitrary value of the chemical potential, the performance of the GANER is superior to that of the NER. The advantages of the GANER are more prominent for a large chemical potential. The results obtained here may provide some guidance for optimally designing solid-state refrigerators. [ABSTRACT FROM AUTHOR]

Large cloud providers are starting to leverage liquid cooling for an increasing number of workloads. Liquid cooling enables providers to overclock server components, but they must tradeoff the potential increase in performance with higher power draw and reliability implications. We argue that two-phase immersion cooling is the most promising technology and, in that context, explore overclocking, its uses, and implications. [ABSTRACT FROM AUTHOR]

High-power salient-pole synchronous motors utilized in high inertia compressor applications in the air separation industry usually exhibit long starting times. During long asynchronous starts, there is a high thermal load induced in the rotor and motor protection becomes more challenging. Long starts are typically defined as run up times that exceed the permissible locked rotor time. The physical and mechanical limits of these motors and their influence on repetitive starts and waiting times are presented. A protection scheme based on current-time characteristics (thermal limit curves) is commonly applied. A general explanation of thermal limit curves and the benefits as well as the limits of these curves is given, for example, the missing ability to display former heat impact and temperature distribution in different parts of the motor. An alternative time-speed-based protection approach is presented. The topic of consecutive starts is discussed along with a method to better utilize the motor thermal capacity. In addition, a procedure to obtain realistic rotor-temperature data from test-field runs and measured data are presented. [ABSTRACT FROM AUTHOR]

Miniaturization high heat flux of power electronic devices have posed a colossal challenge for adequate thermal management. Conventional air-cooling solutions are inadequate for high-performance electronics. Liquid cooling is an alternative solution due to the higher specific heat and latent heat associated with the coolants. Liquid-cooled cold plates are typically manufactured by different approaches, such as skived, forged, extrusion, and electrical discharge machining. When researchers are facing challenges in creating complex geometries in small spaces, 3-D-printing can be a solution. In this article, a 3-D-printed cold plate was designed and characterized with water coolant. The printed metal fin structures were strong enough to undergo pressure from the fluid flow even at high flow rates and small fin structures. A copper block with the top surface area of 1 in $\times \,\,1$ in was used to mimic a computer chip. Experimental data have good match with a simulation model, which was built using commercial software 6SigmaET. Effects of geometry parameters and operating parameters were investigated. The fin diameter was varied from 0.3 to 0.5 mm and the fin height was maintained at 2 mm. A special manifold was designed to maximize the surface contact area between coolant and metal surface and therefore minimize thermal resistance. The flow rate was varied from 0.75 to 2 L/min and the coolant inlet temperature was varied from 25 °C to 48 °C. It was observed that for the coolant inlet temperature 25 °C and aluminum cold plate, the junction temperature was kept below 63.2 °C at an input power of 350 W and the pressure drop did not exceed 23 Kpa. Effects of metal materials used in 3-D-printing on the thermal performance of the cold plate were also studied in detail. [ABSTRACT FROM AUTHOR]

Stress calculation is a key link in evaluating whether the structure of a superconducting magnet is safe. A 35-kV/3.5-MVA single-phase high temperature superconductivity-controllable reactor (HTS-CR) with the HTS winding wound by HTS double pancakes is being developed. The effect on the local stress and temperature rise of HTS double pancakes, which determines the design of the strengthening structure of the HTS double pancake, is studied in this paper. Furthermore, the multiprocess stress development for HTS double pancakes from manufacturing to power-on is also investigated, which discloses the model and the results of the stress calculation. This study can provide a reference for developing HTS-CR with large capacity in the future. [ABSTRACT FROM AUTHOR]

The electron cooling technology is applied in the spectrometer ring (SRing) to improve the luminosity of ion beam for the High Intensity heavy-ion Accelerator Facility (HIAF). The electron cooler consists of a gun section, two 90-degree toroids, a cooling section and a collector section. There are four kinds of main coils used to provide longitudinal magnetic fields along the path of the electron beam. In this paper, we present the modeling and analyzing of the electron cooler magnets by three-dimension software. The optimizing of the magnetic field of cooling section is completed to achieve the required effective cooling length. The magnetic fields along the electron beam path and ion beam path are calculated and the beam trajectory of typical ion is also simulated to offer data for correcting the orbit. [ABSTRACT FROM AUTHOR]

The plasma torch is the key component of the thermal plasma-assisted material processing system. Particularly, direct current (dc) nontransferred arc plasma torch is widely used in high-temperature material processing applications. The characteristics of the thermal plasma jet emanating from the plasma torch depend on many factors, including arc current, type of plasma forming gas, gas flow rates, gas injection configuration, torch geometry, and so on. This experimental study focuses on the comparison between the effects of CO2 and air on the arc voltage, electrothermal efficiency, and specific enthalpy of the plasma torch operated at the atmospheric pressure. For this purpose, a low-power dc plasma torch consisting of a rod-type thoriated tungsten cathode and the copper anode was customized. CO2 and air were used as the plasma forming gases along with a feeble amount of argon (15 lpm). The plasma torch was operated over a wide range of current (100–175 A) with fixed gas flow rates. The $I$ – $V$ characteristics and the electrothermal efficiency of the plasma torch were measured, and results were compared. The maximum electrothermal efficiency and specific enthalpy of the plasma torch when operated with CO2 were reported as 70% and 1900 KJ/Kg, respectively, which is higher than the same torch operated with air as the plasma forming gas. The electron number density and electron temperature of the air and CO2 plasma jet were measured by optical emission spectroscopy (OES). The calculated electron number density and electron temperature of the plasma jet with CO2 were $2.89\times 10\,\,^{\mathrm{ 16}}$ cm−3 and 8598 K, respectively, which is higher than air plasma jet. It was found that CO2 has a stronger influence than air on the arc voltage fluctuation, electrothermal efficiency, and operating regime of the plasma torch. [ABSTRACT FROM AUTHOR]

This paper proposes a load transfer optimization (LTO) model involving hot-spot temperature (HST) and top-oil temperature (TOT) limits of transformers. This work aims to address the overload problem and transformer HST and TOT excursions via LTO. First, the equivalent thermal model for the HST and TOT of transformers under external cooling conditions are discussed, and then the corresponding linearized HST and TOT constraints with varied thermal resistances are derived using the discretization method. Moreover, the proposed LTO model is formulated on the reconfigurable topology of high voltage distribution networks (HVDNs) in China. This proposed LTO model can achieve the optimal network reconfiguration scheme subject to temperature limits and system operation constraints, with the least switching operation cost and the maximum margins of reactive power exchange between HVDNs and transmission systems. Finally, the effectiveness of the proposed LTO model is validated by the modified IEEE-14 node system and the practical HVDNs in China. [ABSTRACT FROM AUTHOR]

Effects of cross flow on the heat transfer and flow characteristics of a circular jet are numerically investigated. The numerical results are compared with the experimental results. Studies have been conducted in the range of Reynolds number (Re) 5100–23 000, dimensionless jet-to-plate spacing ($Z/D$) 2–8, and ratio of cross flow Reynolds number to jet Reynolds number ($\alpha $) 0–2. Heat transfer in the stagnation, transition, and wall jet regions is studied. At all Reynolds numbers, maximum heat transfer is obtained at $Z/D$ = 6. Without cross flow, at higher $Z/D$ and in the range of Reynolds number investigated, maximum heat transfer occurs at the stagnation point. At low $Z/D$ and high Reynolds numbers, there are secondary peaks in the transition region due to the high turbulent kinetic energy (TKE). In certain cases, the Nusselt number at the secondary peak is more than that at the stagnation point. In the wall jet region, the Nusselt number calculated using equivalent flat plate correlations is much lower than the actual values. Cross flow results in increase in peak Nusselt number at low $Z/D$ and $\alpha $. Furthermore, the heat transfer in the upstream region deteriorates and that in the downstream region improves. The degradation in heat transfer is more at smaller $Z/D$. [ABSTRACT FROM AUTHOR]

Aiming at the problem of high winding temperature caused by the large armature winding current of permanent magnet synchronous motor (PMSM) for compressors, a 560 kW PMSM for a compressor was studied. The three dimensional global fluid-heat coupled heat transfer model is established and is discretized by the polyhedral mesh. The fluid and thermal coupling field of a permanent magnet motor are numerically calculated when the rotor rotation is considered. The temperature distribution characteristics of the end windings at different positions are analyzed. Further, the structure of the motor cooling system is improved. The effects of different ventilation modes on the temperature distribution of the motor are compared and analyzed. The temperature distribution of the stator windings under different armature currents is calculated. The calculation results of the end winding temperature are compared with the measured data, verifying the correctness of the calculation method. Conclusions have been obtained that are helpful to the design and operation of the compressor water-cooled permanent magnet synchronous motor. [ABSTRACT FROM AUTHOR]

High-frequency electromagnetic linear machine is one major component for linear eletro-hydraulic actuator that in turn is extrimely important for the flight control of more-electrical or all-electrical aircrafts. The employment of high-frequency linear machine helps to achieve high reliability and dynamic performance of the actuators. However, the capability of heat dissipation of the linear machine unavoidably constrains the input current, which in turn depresses its output performance. Therefore, this paper proposes a novel electromagnetic linear machine based on the self-powered direct oil-cooling windings. Specifically, the windings are immersed into the oil directly, which helps to decrease the temperature of the linear machine significantly and thus increase its output performance. In addition, the oil is pushed by the motion of the mover itself. No additional pump is required any more. Thus, the system can be simplified greatly. The design concept of high-frequency electromagnetic linear machine along with its operating principle is presented. A high-precision three-dimensional (3D) piecewise modeling method is proposed to simultaneously consider axial, radial and circumferential equivalent thermal circuits. Numerical simulation is conduced to validated the analytical model. A research prototype of the linear oscillating machine based on direct oil-cooling windings is developed and empolyed for experimental study, and the experimental result verifies the mathematical model of the thermal field well. [ABSTRACT FROM AUTHOR]

Here, we demonstrate holey silicon-based thermoelectric cooling devices using simple fabrication processes and evaluate their cooling performance using infrared thermography. While lateral thermoelectric coolers require a suspended structure and thermal isolation for optimal performance, our design simply combines a silicon device layer with an insulating Pyrex substrate and enables demonstration of thermoelectric cooling by holey silicon even on a bulk heating stage instead of a local hot spot. Our work shows that holey silicon with $1.9~\mu \text{m}$ wide necks and 21 $\mu \text{m}$ deep trenches provides a temperature reduction of 1.2 °C over a 300 $\mu \text{m}\,\,\times $ 300 $\mu \text{m}$ area when the underlying heating stage is set to keep the background at $100~^{\circ }\text{C}$. Our model attributes the cooling performance to the unique thermal anisotropy of holey silicon and predicts greater performance with deeper holey silicon trenches, smaller holey silicon necks, and higher background temperatures or stronger heating. These findings indicate holey silicon-based thermoelectric cooling can be very useful for thermal management of various electronic devices and handling on- chip hot spots. [ABSTRACT FROM AUTHOR]

The electrical conductivity (EC) of additively manufactured conductors can be purposely controlled by changing as-built orientation and postprocessing conditions. This feature can be leveraged to minimize winding alternate current (ac) losses in electrical machines adopting solid conductors. This article deals with the additive-manufacturing-based winding design of a high-specific-power permanent-magnet (PM) machine for aerospace applications. Specifically, conductors near slot opening are designed with low EC to reduce winding AC losses, while conductors near slot bottom adopt higher EC to reduce direct current (DC) losses. Parametric finite element models are developed for a thorough design parametric analysis targeting high-specific power as well as high efficiency. The implementation of the proposed coil concept with inhomogeneous EC is discussed and demonstrated. The EC measurements on rod and coil samples are conducted for material characterization. [ABSTRACT FROM AUTHOR]

This work aims to improve the combined flow and thermal network (CFTN) accuracy for radially air-cooled generators by investigating the possible error stemming from the flow part. The nonlinear resistance characteristics of the T-junction dividing flow are first time considered for such cooling arrangement, which is achieved by employing the Gardel equations and the blend equation as the governing equations. Compared with the CFD model results as the benchmark, the nonlinear CFTN predicts an accurate flow rate in the radially extended airducts, making only 9% root mean square (rms) error for all the airducts. On the contrary, the linear CFTN fails to obtain a reliable flow distribution, as the rms error is as large as 34%. As a result, the nonlinear CFTN improves the accuracy of the maximum winding temperature by 6.4% over the linear CFTN and gives a more reasonable temperature gradient in the axial direction. Furthermore, the relative difference between the linear and nonlinear CFTNs is found to be even larger in the following conditions: large cooling air flow rate, wide airgap, low slot fill factor, and large airduct number. The proposed nonlinear CFTN modeling approach is also validated against experimental measurements for a prototype. The modeled temperatures match well with the measurements at different axial positions. According to the aforementioned findings, the nonlinear CFTN modeling approach is considered to be a reliable thermal analysis tool for the radial air-cooling arrangement. [ABSTRACT FROM AUTHOR]

This article proposes an efficient thermoelectric temperature control system based on an improved proportional integral differential (PID) algorithm in which energy feedback technology is used to enhance thermoelectric cooling. In the proposed power management system, two groups of batteries are efficiently and alternatingly charged and discharged such that the information of the circuit can be monitored in real time. The PID algorithm is improved by using the idea of a state machine to control the thermoelectric coolers (TEC) through an H-bridge circuit with pulsewidth modulation. Finally, the energy feedback circuit combined with improved synchronous switching technology is designed to recycle the energy to drive the sensor. By inputting current of 3.1 A, a wide range of temperature control from 1.437 to 60.187 °C was implemented. While targeting a temperature of 10 °C at an ambient temperature of 22 °C, the proposed temperature control system had a control time of 30.5 s, compared with 287 s when using the conventional method, with an accuracy of 0.1 °C, and an error of only ±0.35 °C. The results confirm that electric energy at a peak voltage of 1.2 V and current of 24 μA can be recovered. The proposed energy feedback system can thus improve the efficiency of energy utilization of TEC from a peripheral circuit. [ABSTRACT FROM AUTHOR]

This article deals with metal-oxide varistor (MOV) and resistor–capacitor–diode (RCD) snubber-based solid-state circuit breakers (SSCBs). There are two main contributions. First, a design methodology of MOV-RCD snubber parameters is proposed by considering thermal dissipation and snubber charging time for the first time. The thermal profile of the main conduction switches determines nominal current under passive cooling. Based on the nominal current, the fault current magnitude is derived, and a design method of key parameters of an MOV-RCD snubber is proposed. Four snubbers are designed with different fault currents and dc voltages. Second, symmetrical layouts with distributed parallel cells are proposed for high current capability, which enables scalability. Q3D simulations facilitate the evenly distributed stray inductances among paralleled branches. Both low- and medium-voltage SSCBs are implemented, ranging from 500 V/300 A to 2 kV/1 kA. The power density achieves 37.8 kW/L at 500 V/1 kA. Experiments demonstrate that the reverse voltage reaches 4.88 kV with an ultrafast interruption speed of 24 μs for 2 kV/1.144 kA fault current including the MOV conduction time interval. [ABSTRACT FROM AUTHOR]

Silicon carbide (SiC) power modules are attractive in many applications due to the superiority of their semiconductor characteristics. However, power modules are subjected to repetitive thermo-mechanical stress caused by the mismatch of the coefficient of thermal expansion between different layers of materials. Moreover, 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. To tackle these challenges, this article 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 new design, SiC mosfet bare dies are directly soldered on the top of VC-PCHS, which not only act as heat spreaders but also conduct the drain current of mosfets. The integrated VC-PCHS is optimized based on thermal and thermomechanical performance. An 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 article 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. [ABSTRACT FROM AUTHOR]

In this article, we address the problem of accurate full-chip power and thermal map estimation for commercial off-the-shelf multicore processors. Processors operating with heat sink cooling remains a challenging problem due to the difficulty in direct measurement. We first propose an accurate full-chip steady-state power density map estimation method for commercial multicore microprocessors. The new method consists of a few steps. First, 2-D spatial Laplace operation is performed on the measured thermal maps (images) without heat sink to obtain the so-called raw power maps. Then, a novel scheme is developed to generate the true power density maps from the raw power density maps. The new approach is based on thermal measurements of the processor with back-side cooling using an advanced infrared (IR) thermal imaging system. FEM thermal model constructed in COMSOL Multiphysics is used to validate the estimated power density maps and thermal conductivity. Later, this work creates a high-fidelity FEM thermal model with heat sink and reconstructs the full-chip thermal maps while the heat sink is on. Ensuring that power maps are similar under back cooling and heat sink cooling settings, the reconstructed thermal maps are verified by the matching between the on-chip thermal sensor readings and the corresponding elements of thermal maps. Experiments on an Intel i7-8650U 4-core processor with back cooling shows 96% similarity (2-D correlation) between the measured thermal maps and the thermal maps reconstructed from the estimated power maps, with 1.3 °C average absolute error. Under heat sink cooling, the average absolute error is 2.2 °C over a 56 °C temperature range and about 3.9% error between the computed and the real thermal maps at the sensor locations. Furthermore, the proposed power map estimation method achieves higher resolution and at least $100\times $ speedup than a recently proposed state-of-art Blind Power Identification method. [ABSTRACT FROM AUTHOR]

With the every-increasing demands for miniaturization, the efficient cooling techniques for axial-flux permanent magnet synchronous machines (AF-PMSMs) have attracted great attentions. In this paper, the thermofluid behaviors of a 7-kW 4000-rpm AF-PMSM are numerically investigated based on a coupled model, and the computations are validated by thermal tests performed on the AF-PMSM prototype. To enhance the heat dissipation capacity of the rotor components, it is proposed a self-circulated oil hermetically cooling system, for which the cooling liquid circulates in a hollow shaft. During operation, the oil flow driven by the centrifugal blades forms a closed oil circuit, and can create an effective heat flow path from the hot areas to the cold regions. The oil cooling system is employed in the AF-PMSM to effectively maintain, and evenly distribute, the motor temperature rise. The cooling effectiveness is proved by fluid flow and thermal coupled analyses. To further improve the heat dissipation capacity, the self-circulated oil-cooling structure is modified based on the calculated fluid flow distribution. Finally, the structural parameters are optimized by Taguchi method to minimize both the temperature rise and the rotor weight increment, and the optimization results are numerically and experimentally validated. [ABSTRACT FROM AUTHOR]

The design of the China Fusion Engineering Test Reactor (CFETR) device is one of the main tasks in the next stage of research on fusion energy in China. The CFETR divertor is a key in-vessel plasma-facing component, which will suffer from sputtering erosion and exfoliation caused by intense plasma bombardment, severe heat fluxes, and neutron irradiation. Due to neutron activation of in-vessel components, remote handling (RH) technology has been considered as one of the essential issues of the CFETR divertor. In this article, a new concept of an integral hybrid divertor blanket for the CFETR is proposed, which is feasible for installation and disassembly in CFETR vacuum vessel by RH. Dome is an important part of the CFETR divertor, which comprises 80 modules, and each module is composed of flat-type plasma-facing units (PFUs), steel supports (SSs), and RH compatible structures. Every Dome module is connected to the CFETR blanket by RH compatible structures. This article mainly carries out the conceptual design of Dome (option), degree of freedom (DOF) analysis, stability analysis, RH process planning, and flow field analysis of cooling scheme, which will provide a solid foundation for its subsequent thermal-hydraulic analysis. [ABSTRACT FROM AUTHOR]

Recent breakthroughs in Neural Networks (NNs) led to significant accuracy improvements of several machine learning applications such as image classification and voice recognition. However, this accuracy improvement comes at the cost of an immense increase in computation demands. NNs became one of the most common and computationally intensive workloads in today's datacenters. To address these computational demands, Google announced in 2016 the Tensor Processing Unit (TPU), an advanced custom ASIC accelerator for NN inference. Two new TPU versions (v2 and v3) followed in 2017 and 2018 that support also training. Google TPUv3 packs an immense processing power ($\mathrm{90TFLOPS}$ 90 TFLOPS per chip) in a tiny and condensed area, leading to very high on-chip power densities and thus excessive temperature. In this article, superlattice thermoelectric cooling, which is one of the emerging on-chip cooling, is considered as an advanced cooling example for Google TPU and we investigate the impact of Negative Capacitance FET (NCFET), which is one of the recent emerging technologies, on the cooling and efficiency of TPU. Through full-chip design, of the computational core of the TPU, based on $14\mathrm{nm}$ 14 nm Intel FinFET technology and multiphysics temperature simulations, we demonstrate that NCFET can significantly minimize the required cooling-cost. More than 4000 NCFET configurations are evaluated in order to traverse the entire design space defined by the thickness of the ferroelectric layer of NCFET, the operating voltage, cooling, and the operating frequency, in addition to all possible FinFET's configurations. Moreover, our experimental evaluation shows that by eliminating the cooling cost, NCFET delivers 2.8x higher efficiency compared to the conventional FinFET baseline. [ABSTRACT FROM AUTHOR]

In this article, a dc-link structure feasible for integration with the circumscribing polygon modular integrated drives is proposed. The proposed dc-link structure combines both the dc-link capacitors and the bus-bar together and integrates them with the machine and the converter modules without increasing the outer diameter of the integrated machine/converter structure. A generic design methodology for the proposed dc-link structure is provided and applied on a reconfigurable 15 stator coils concentrated winding axial flux machine for all its possible phase configurations. The design methodology presented in this article involves the determination of the required dc-link capacitance and the multiphysics design of the bus-bar. The parasitics of the bus-bar part of the proposed dc-link structure are evaluated using electromagnetic finite element method (FEM) models and their influence on the dc-link waveforms is evaluated. Due to the expected high ambient temperature inside an integrated drive, electromagnetic and computational fluid dynamics (CFD) models are developed for the proposed dc-link structure to evaluate the loss density and the temperature distribution of the bus-bar to ensure reliable operation. An experimental setup is built to validate the design methodology. [ABSTRACT FROM AUTHOR]

In this article, we show the feasibility of improving the performance of a high voltage and high repetition avalanche transistor pulse generator by applying a two-phase immersion cooling technique. The forced air cooling, single-phase immersion cooling, and two-phase immersion cooling techniques were applied to a 60-stage subnanosecond pulse generator. The experimental results indicate that the two-phase immersion cooling technique can effectively control the temperature rising of the avalanche transistor and, thus, reduce the time base jitter and voltage amplitude jitter. Five types of dielectric fluid with different boiling temperatures were comparatively studied. The FC-72 was finally adopted for the balanced performance on voltage amplitude and repetition rate. The two-phase immersion cooling technique could reduce the thermal resistance between the case and ambient and increase the maximum power from 330 to 876 mW. With this cooling method, the surface temperature of the transistor can be effectively controlled below 62 °C. The pulse generator could achieve outstanding performance with a voltage of 2350 V and a rise time of 180 ps. It can work stably at 200 kHz for more than 30 min, and the burst repetition rate could be 260 kHz within 1 min. This article offers new perspectives in the design of high repetitive avalanche transistorized subnanosecond generators. [ABSTRACT FROM AUTHOR]

One of the common applications of high-temperature superconductors is levitation transport. Recently, a number of works have been aimed at increasing the levitation force of levitation transport by using the repulsive force between permanent magnets. The use of permanent magnets significantly increases the levitation force, but also greatly reduces the lateral stability of the system. Then the main role of the superconductor is vertical and lateral stabilization of the system. In our work, we present new experimental results on the study of the levitation force and lateral stability of hybrid maglev systems of various configurations. Configurations are considered when the superconductor is between two magnet assemblies and when the superconductor and the carriage magnet assembly are arranged in series along the guidway. A commercially available 12 mm wide CC-tape manufactured by SuperOx was used for measurements. Both the vertical levitation force and the lateral restoring force were measured. Based on the experimental data, we concluded that the configuration with the separate arrangement of the carriage magnets and the tape stack is more advantageous from the point of view of the stability of the levitation force and the lateral stability of the system. The results obtained may be relevant for the development of hybrid levitation systems using permanent magnets to increase the levitation force. [ABSTRACT FROM AUTHOR]

The rotor temperature rise of high voltage line-start solid rotor permanent magnet synchronous motors (HVLSSR-PMSMs) may be too high while operating, which properly causes thermal demagnetization for permanent magnets. Therefore, it is necessary to perform the thermal investigation on HVLSSR-PMSM. In this article, a 315-kW, 6-kV HVLSSR-PMSM with the air-cooled hybrid ventilation system is studied in the view of thermal phase. The losses, obtained from the electromagnetic analyses, are applied to the thermal investigation as the distributed heat sources. Whereas, both the mathematical and the geometrical models are proposed for the three-dimensional (3-D) fluid-thermal coupled investigation, from which the fluid velocity and the temperature in motor different components are determined. Whereas, with the hybrid ventilation system, temperatures in motor different components reduce, obviously comparing with those in motor with the original cooling system. The experimental investigations are performed on prototypes in both cases, which verify the calculation results and approve the effectiveness of the proposed hybrid air cooling system as well. [ABSTRACT FROM AUTHOR]

Double-sided cooling based on planar packaging method features better thermal performance than traditional single-sided cooling based on wire bonds. However, this method still faces thermal and electrical challenges in multichip SiC power modules. Specifically, one is severe thermal coupling among parallel bare dies, and the other is unbalanced current sharing due to unreasonable layout design. This article aims to explore the potentials of SiC power devices in power module, which are higher current capability and reliability. The proposed packaging method is called interleaved planar packaging and can get rid of the optimizing contradiction between thermal and electrical performance. In this packaging method, there are two functional units: interleaved switch unit and current commutator structure. Benefited from the two units’ electromagnetic and thermal decoupling effects, the interleaved power module features low loop inductance, balanced current, low coupling thermal resistance, and even thermal distributions. A 1200 V 3.25 mΩ half-bridge SiC power module based on interleaved planar packaging is fabricated and tested to verify this method's superiority. [ABSTRACT FROM AUTHOR]

Critical heat flux (CHF) is regarded as one of the major problems in cooling system design. Specifically, because the tokamak is loaded with heat flux of several megawatts per square meter, carefully considering the CHF is crucial. This study analyzes the subcooled flow boiling CHF of the swirl tube under one-side high-heat load condition. The CHF parametric analysis results indicate that smaller swirl tape twist ratios yield higher swirl flows. As the subcooling increases, the CHF increases because the vapor inside the channel condensates more rapidly due to the lower bulk temperature. And the increase of the mass flow rate also increases the CHF because it enhances the forced convection heat-transfer performance. However, the CHF slightly decreases as the latent heat decreases with the increase in pressure. The assessment of existing CHF subcooled flow boiling indicates that the formulated correlations based on the smooth tube mainly tend to yield under-predicted results. However, most of the correlations developed according to the swirl tube tend to over-predict. Among these, the Nariai and Inasaka swirl CHF correlation has the lowest error rate; nevertheless, it tends to slightly under-predict results because of the difference between uniform and one-side heating. Accordingly, a new modified Nariai and Inasaka correlation is formulated using a Python code and artificial intelligence technology to reflect the one-side heating effect. [ABSTRACT FROM AUTHOR]

Herein, the heat-transfer characteristics of the subcooled flow boiling of swirl tubes are evaluated experimentally under one-side high heat load conditions. As the twist ratio of the tape decreased and the flow rate increased, the forced convective heat transfer was enhanced; thus, the single-phase heat transfer was enhanced, and the onset of nucleate boiling (ONB) heat flux increased. As the degree of subcooling increased, the ONB heat flux increased because of the faster condensation rate. As the pressure increased, the ONB heat flux increased, and the critical heat flux increased, due to the suppression of boiling and the decrease in the bubble size. The authors analyzed the heat transfer characteristics of the one-side heated swirl tube in the single-phase regime, the partially developed nucleate boiling (PDB) regime, and the fully developed nucleate (FDB) boiling regime. And the prediction performance of the existing heat-transfer correlations developed for application to each regime was evaluated. The PDB correlations showed a mean absolute error rate (MAE) of approximately 30%. However, the existing FDB correlations a high error rate (MAE higher than 48%) at a high heat flux of several MW/M2 outside the developed experimental range. Therefore, we develop a new swirl tube FDB heat-transfer correlation that can also be used in the development of a swirl tube flow boiling map using the Python code grafted with the artificial intelligence (AI) regression method. [ABSTRACT FROM AUTHOR]

For installation in the public electric power grid of the city of Augsburg, Germany, a resistive superconducting fault current limiter (SFCL) was designed, constructed, tested and operated in the framework of a partially funded project ‘ASSiST’. Right from the beginning, it was agreed to aim for a prolonged operation even after closure of the project. This endeavor has been started due to a fundamental need to limit the prospective fault currents at a feeder point of the grid and in order to create long-term operational experience on a device seamlessly integrated into commercial grid components and switchgear, thus demonstrating a high level of readiness for widespread application. It revealed that the SFCL was of robust design – withstanding all electrical tests including a special two-phase fault and sustaining stable cryogenic conditions even during partial outages of the cooling system – and that the technology is reducing loss by shunt reactors. Furthermore, due to the control equipment on medium voltage level, valuable insights on grid behavior could be gained. The extended operation for 4 years has clearly shown the performance and robustness of SFCL technology in feeder points on MV level and provides a reference point for further commercialization. [ABSTRACT FROM AUTHOR]

Transition curvature is a major contributor to transition broadening in current heat-assisted magnetic recording (HAMR) devices. In this article, in order to clarify HAMR performance versus bit length (BL), a detailed study of the dependence of HAMR transition curvature on BL is presented. With the help of micromagnetic simulations, HAMR bits with three different BLs (10.5, 15, and 21 nm) are written and transition curvatures are calculated. Both thermal exchange coupling composite (ECC) media and pure FePt media are tested. By tracking the change of transition curvature during the HAMR cooling process, an erase-after-write effect is observed. DC-erased media, introduction of intergranular exchange, and removal of dipole interactions are also examined for potential optimization of the HAMR system. [ABSTRACT FROM AUTHOR]

Linear voice coil motors (VCMs) are widely used in some high precision or high dynamic applications, such as lithography, digital cameras, and microscopes. In this article, a high thrust linear VCM is analyzed and designed, which is used for the position loop stiffness test of linear motor servo system. To guarantee the structural strength of coil frame and provide space for the cooling channels, the two layers’ coil arrangement is adopted. Based on 2-D finite element method (FEM), the thrust and thrust ripple performance of the motor are analyzed. Moreover, a reasonable cooling structure integrated with the coil frame is designed to further improve the thrust density. Finally, a linear VCM prototype with a thrust rating of 1000 N is manufactured and tested. The static thrust test results show that the thrust varies linearly with the coil current. The motor can provide a nearly constant thrust and thrust ripple within ±2 mm displacement is less than 1%, which agrees well with finite element simulation. In addition, the temperature test is also achieved. Compared with natural cooling condition, the thermal equilibrium can be achieved among the coil, coil frame and cooling water with the water-cooling condition, when the current density is 15.3 A/mm2. Furthermore, a good overall cooling effect and low surface temperature rise can be realized when two heat shield cover plates are fixed onto both sides of the primary. [ABSTRACT FROM AUTHOR]

In this article, a low-loss RF coaxial through-silicon vias (TSVs) (C-TSVs) configuration in the silicon interposer with the embedded cooling cavity is proposed. For the single C-TSV array passing through the embedded cooling cavity, the transmission losses with different coolants were compared. The insertion loss immersed in FC770 is 0.14 dB at 40 GHz, which is closed to the typical C-TSV interposer (0.2 dB). It is much smaller than the deionized water (6.49 dB) one. The optimal spacing of multiple C-TSV arrays filled with FC770 coolant is $600~\mu \text{m}$ (vertical transmission of 0.16 dB at 40 GHz). When the cooling cavity is embedded in the interposer with FC770 coolant, the maximum surface temperature of the power devices can be less than 56.8 °C at 250 W/cm2 heat flux. Compared with the solid silicon interposer, the maximum von Mises thermal stress of the C-TSV interposer with the embedded cooling cavity can be reduced by 44.8%. [ABSTRACT FROM AUTHOR]