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This article deals with a comprehensive analysis and performance evaluation of a fully integrated two-phase cooling system for power converters. A suitable test bed has been properly manufactured to perform the experimental campaign for the evaluation of the benefits and to deploy a dedicated management procedure of the two-phase cooling. The system is tested under real operating conditions, in which the system is employed for cooling a 1200-V 100-A insulated-gate bipolar transistor (IGBT) power module of an inverter controlling a permanent magnet synchronous machine. The experimental results show the inverter temperature behavior in start-up for different flow rates of coolant and different temperatures of the fluid on the secondary system. In the steady-state operation, using lower coolant flow rates in the primary circuit achieved equal or even better cooling for the IGBT module compared with higher flow rates. With respect to traditional cooling approaches, the proposed arrangement allows a greater extraction of the heat at a very low flow rate of the cooling fluid, even with standard industrial grade heat sinks, which motivates the use of this cooling technology for the next generation of power electronics converters.

High power-density electric machines present the benefits of high torque and speed. However, this generally comes with heating problems characterized by high temperatures that affect performance. Conventional approaches to address overheating are to include cooling fans or jackets within the stator core of the machine. This approach is challenging to implement in small-size high power-density machines. In this article, a cooling mechanism integrated in the rotor of a high power-density permanent magnet motor is proposed. It comprises a set of six holes, shrouded within a hollow shaft. The mechanism is based on conditioning air due to a centrifugal force that is produced by the rotational speed of the rotor from the inlet. A theoretical model based on flow resistance network is proposed to analyze the airflow rate. An analytical thermal model based on lumped parameter thermal network is developed to analyze the effect of the flow rate on the temperature distribution in the motor. Also, a simulation analysis model was conducted using computational fluid dynamics to analyze the effect of air flowing in the motor. An experimental prototype is developed to verify, validate, and evaluate the proposed cooling model. The cooling system is effective in reducing temperatures from speeds above 6000 min−1.

The impact of heating and cooling cycles on a copolymer mixture of urethane dimethacrylate (UDMA) and triethylene glycol dimethacrylate (TEGDMA), with and without gold nanorod doping was studied by using in-situ Raman spectroscopy. The copolymer was made in a 3:1 ratio and 0.1236 m/m% concentration of 25 nm × 85 nm gold nanorods was added. Heating and cooling between 30 °C and 140 °C was applied and two distinct vibration bands at 1447 cm-1 (C–H bond) and 1638 cm-1 (methacrylate C = C stretching) were monitored using 532, 633 and 785 nm excitations. The degree of conversion (DC) of the polymer was calculated based on the peak intensities. The influence of the gold nanorods, single and multiple thermal cycles, excitation wavelength, and reference peak selection on the calculated DC were analyzed in detail. [ABSTRACT FROM AUTHOR]

This article proposes a novel condition monitoring method for heatsink of traction inverter of urban rail train by detecting the change of temperature dynamic curves. Artificial neural network is used to predict the reference curves of healthy state under various working conditions, and the differences between temperature dynamic curves are extracted by one-way distance algorithm. This method is suitable for the condition monitoring of heatsink of urban rail train, because first it meets the diversity of operation conditions and nonthermal equilibrium state of traction inverter. Moreover, its implementation does not cause intrusion to the original system, and can realize online monitoring. Finally, the effectiveness is experimentally verified. [ABSTRACT FROM AUTHOR]

A method to derive the junction-to-case level coupling thermal resistances among paralleling chips in the multichip semiconductor power module has been proposed in this article. It is revealed that the traditional structure function methodology (SFM), which is developed for analyzing the self-heating effect of the driving-point chip, cannot be applied directly in the thermal coupling analysis, where the influence of the driving-point chip on the neighboring acceptor chip is concerned. This article shows that by combining the traditional SFM with the frequency-domain analysis (FDA), the effective separation points between the module case and the external cooling setup can be identified in both time and frequency domains, which correspond to the characteristic frequency points in the complex loci of the thermal impedance curves. By extracting the amplitudes at the characteristic frequencies from the complex loci in the FDA, the junction-to-case level coupling thermal resistances can be derived. Both simulation and experimental study have been carried out to verify the concept. The agreement between the two justifies the proposed method. [ABSTRACT FROM AUTHOR]

The double-side cooling (DSC) packaging becomes more and more popular with the great demands of high power and fast speed, especially for silicon carbide metal oxide semiconductor field effect transistors. Measurements and modeling of thermal resistance are critical for thermal management of DSC module. However, the thermal resistance of DSC module is still unclear due to the asymmetric dual thermal paths. In this article, a clear understanding of thermal resistance of DSC module measured by transient dual-interface method (TDIM) is explained. The thermal impedance of DSC module is analyzed through time- and frequency-domain response of the DSC thermal model. The cooling conditions in TDIM have no influence on the measured thermal resistance of DSC module. The measured thermal resistance from junction to top case (or bottom case) is half of the actual value. The important conclusions are verified by transient simulations and experiments. Based on the results, a new definition of thermal resistance of DSC module is proposed for exact evaluation of thermal resistance and reliability. [ABSTRACT FROM AUTHOR]

High voltage insulation and thermal management are the two major challenges in a high-power medium frequency transformer (MFT) design. This letter proposes novel insulation and cooling structure with potted windings in a 100 kW MFT with two FINEMET FT-3TL magnetic cores and parallel-concentric winding structure. For the first time, a three-dimensional printed bobbin with heatsink fins is demonstrated. The 100 kW MFT achieves a power density of 10.6 kW/L and a partial discharge inception voltage of 20 kV peak. The MFT is applied in a dual active bridge based medium voltage solid state transformer, achieving a peak efficiency of 98.2% at 40 kW and 97.5% at 100 kW. The MFT itself has a 99.735% efficiency with superior thermal performance at 100 kW output power. [ABSTRACT FROM AUTHOR]

The power density in modern Integrated Circuits (ICs) is tremendous. For example, Multi-Processor Systems-on-Chip (MPSoCs) nowadays undergo temperature swings of 40 degrees in 100 milliseconds or less, with rapidly emerging and vanishing sub-millimeter hot spots. As such, not only a simulation-based cooling assessment is vital, but one has to simulate the on-chip thermal phenomena jointly with the heat dissipation system - historically, a challenge. In recent years, however, the idea of coupling traditional 3D chip simulators with heat dissipation models written in Equation-Based Modeling (EBM) languages has proven to be a game changer. EBM languages allow one to compose a model by assembling components described in terms of Differential and Algebraic Equations (DAE) and have the simulation code generated automatically. In this article, we take a tutorial viewpoint on the matter just sketched, to put the reader in the position of exploiting the above technology. We also present the first nucleus of a model library for cooling systems, that we release as free software for the scientific and engineering community. [ABSTRACT FROM AUTHOR]

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]

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]

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]

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]

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]

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]

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]

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]

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]

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]

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 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 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]

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]

We formulate a model predictive control (MPC) for linear time-invariant systems based on H-infinity loop-shaping. The design results in a closed-loop system that includes a state estimator and attains an optimized stability margin. Input and output weights are designed in the frequency domain to satisfy steady-state and transient performance requirements, in lieu of standard MPC plant model augmentations. The H-infinity loop-shaping synthesis results in an observer-based state feedback structure. An inverse optimal control problem is solved to construct the MPC cost function, so that the control input computed by MPC is equal to the H-infinity control input when the constraints are inactive. The MPC inherits the closed-loop performance and stability margin of the loop-shaped design when constraints are inactive. We apply the methodology to a multizone heat pump, and validate the results in simulations and laboratory experiments. The design rejects constant unmeasured disturbances, tracks constant references with zero steady-state error, meets transient performance requirements, provides an excellent stability margin, and enforces input and output constraints. [ABSTRACT FROM AUTHOR]

Accurate load forecasting is the key to economic dispatch and efficient operation of Multi-Energy System (MES). This paper proposes a combined load forecasting method for MES based on Bi-directional Long Short-Term Memory (BiLSTM) multi-task learning. Firstly, this paper investigates the multi-energy interaction mechanism and multi-loads characteristics and analyzes the correlation of multi-loads in different seasons. Then, a combined load forecasting method is proposed, which focuses on making full use of the coupling relationship among multiple loads. In the forecasting model, the different loads are selected combinedly as the input features according to the Maximum Information Coefficient (MIC). The multi-task learning is adopted to construct the cooling, heating and electric combined load forecasting model based on the BiLSTM algorithm, which can effectively share the coupling information among the loads. Finally, case studies verify the effectiveness and superiority of the proposed method in both learning speed and forecasting accuracy. [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]

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]

The battery thermal management (BTM) system plays an increasingly important role today in the safety of electric vehicles (EVs) and hybrid electric vehicles (HEVs) as the battery capacity and power ratings keep growing. The BTM system is commonly coupled with the vehicle passenger cabin HVAC system. This integrated thermal system is a major onboard energy consumer, and its complexity brings challenges to its control. With the planned-ahead speed profile and the corresponding power trajectory obtained from the connected and automated vehicle (CAV) technology, predictive control makes a desirable option for the integrated system to maintain battery safety and passenger comfort while lowering energy consumption. However, in order to achieve both high accuracy and low cost in a wide control range, a very long prediction horizon and high sampling rate are both necessary. This will overwhelm the processing capacity of the onboard electronic control unit (ECU) if using conventional predictive control. In this paper, a two-stage predictive control strategy for the BTM and HVAC coupled system is proposed to solve this problem. In stage 1, based on the integrated cooling system efficiency features, a hierarchical and iterative dynamic programming (HIDP) scheme is designed to derive the optimal battery temperature trajectory to reach the set point at the end of the horizon with a modest computation burden. In stage 2, a control-oriented model is constructed for the cooling system and a model predictive controller (MPC) is accordingly built to track the trajectory from Stage 1 while enforcing the energy saving. A high set-point-tracking performance and as high as 10.61% energy saving for the cooling system in the UDDS cycle are verified by simulation results. The real-time implementation capability of the proposed strategy is demonstrated by the vehicle emulator experiments based on hardware in the loop (HIL) and a rapid control prototyping (RCP) platform. [ABSTRACT FROM AUTHOR]

An array of trapped atomic ions that are laser cooled and isolated in an ultrahigh-vacuum environment presents one of the most advanced physical platforms for realizing a practical quantum computer. Small-scale ion quantum computers up to tens of ions have been built and achieved the highest fidelities on elementary quantum operations and overall quantum volume (QV). This article provides an overview of the elements of trapped-ion quantum computing (TIQC), current achievements in the field, and future perspectives. [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]

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]

Jointly managing water and energy systems, rather than treating each system independently, is recognised as an approach that can lead to a more cost-effective and reliable supply, which is particularly critical in water-rich and developing countries. This has motivated the development of various integrated water-energy simulators, each one catering for specific modelling needs through the use of specific sets of modelling assumptions, e.g., representing water and energy with balance equations, or dedicated river flow and power network equations. In this context, it becomes critical to assess the effectiveness of different modelling assumptions to improve the design of water-energy simulators. In particular, it is important to develop a methodology that can identify, based on a systematic assessment process, the portfolios of modelling assumptions that better capture the uncertain future conditions in the water and energy sectors, e.g., climate-driven stresses and shocks such as water scarcity, temperature rise, etc. To address this challenge, this paper proposes a Mixed Integer Linear Programming (MILP) integrated water-energy system simulation methodology designed to adapt and quantify different modelling assumptions under various weather-related conditions (e.g., water scarcity and high temperatures). The models were developed to capture the characteristics of non-pressurised water systems (e.g., channels and rivers) and electricity systems. The methodology is used to investigate typical modelling assumptions (e.g., temporal resolutions and water and power system models) and novel approaches to model the impacts of high temperatures on generation capacity to capture the effects of extreme weather on power generation. The methodology is demonstrated on the Ghanaian integrated water-energy system. The results highlight the benefits in terms of computational costs and modelling accuracy, of the customisable simulation, and provide guidance to select adequate modelling assumptions. [ABSTRACT FROM AUTHOR]

Therapeutic hypothermia (TH) is a common and effective technique to reduce inflammation and induce neuroprotection across a variety of diseases. Focal TH of the brain can avoid the side effects of systemic cooling. The degree and extent of focal TH are a function of cooling probe design and local brain thermoregulation processes. To refine focal TH probe design, with application-specific optimization, we develop precise computational models of brain thermodynamics under intense local cooling. Here, we present a novel multiphysics in silico model that can accurately predict brain response to focal cooling. The model was parameterized from previously described values of metabolic activity, thermal conductivity, and temperature-dependent cerebral perfusion. The model was validated experimentally using data from clinical cases where local cooling was induced intracranially and brain temperatures monitored in real-time with MR thermometry. The validated model was then used to identify optimal design probe parameters to maximize volumetric TH, including considering three stratifications of cooling (mild, moderate, and profound) to produce Volume of Tissue Cooled (VOTC) maps. We report cooling radius increases in a nearly linear fashion with probe length and decreasing probe surface temperature. [ABSTRACT FROM AUTHOR]

Cold sensations of varying intensities are perceived when human skin is subject to diverse environments. The accurate presentation of temperature changes is important to elicit immersive sensations in applications such as virtual reality. In this article, we developed a method to elicit intensity-adjustable non-contact cold sensations based on the vortex effect. We applied this effect to generate cold air at approximately 0 $^\circ$ C and varied the skin temperature over a wide range. The perception of different temperatures can be elicited by adjusting the volume flow rate of the cold air. Additionally, we introduced a cooling model to relate the changes in skin temperature to various parameters such as the cold air volume flow rate and distance from the cold air outlet to the skin. For validation, we conducted measurement experiments and found that our model can estimate the change in skin temperature with a root mean-square error of 0.16 $^\circ$ C. Furthermore, we evaluated the performance of a prototype in psychophysical cold discrimination experiments based on the discrimination threshold. Thus, cold sensations of varying intensities can be generated by varying the parameters. These cold sensations can be combined with images, sounds, and other stimuli to create an immersive and realistic artificial environment. [ABSTRACT FROM AUTHOR]

In this work, whole metal oxide-based p-NiO/i-Ga2O3-i-Al2O3:Ga2O3 multiple quantum wells (MQWs)/n-HfO2:Ga2O3 deep ultraviolet light-emitting diodes (DUV-LEDs) were manufactured and studied. To investigate the improved luminance of the MQWs, single i-Ga2O3 active layer was utilized to replace MQWs in the DUV-LEDs. The vapor cooling condensation system was used to deposit n-HfO2:Ga2O3, i-Ga2O3, and i-Al2O3:Ga2O3 films on sapphire substrate. Besides, the radio frequency magnetron sputtering system was used to deposit p-NiO film onto the MQWs. As the measurement of electroluminescence spectra, the peak emission wavelength of both the devices with MQWs and i-Ga2O3 active layer was approximately 243 nm. Compared with the utilization of single i-Ga2O3 active layer, the peak luminance intensity of the DUV-LEDs with MQWs was enhanced due to the effective carrier recombination in the i-Ga2O3 well caused by the effective carrier block of the i-Al2O3:Ga2O3 barrier in the MQWs. [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]

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]

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]

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]

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]

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]

Memory security has recently come into the spotlight as attackers have stepped up their efforts to gain illicit access to sensitive data or cause denial-of-memory service via a variety of avenues, such as cold boot attacks, bus snooping, and physical probing or tampering. In this letter, we propose SuperVAULT, a novel secure storage solution for protecting secret data/keys by exploiting the superparamagnetic regime of nanomagnets. Through materials and dimensional engineering of the magnetic tunnel junction (MTJ) free layer, the energy barrier of spin-transfer torque magnetoresistive random-access memory (STT-MRAM) cells can be designed to lie in the range of the thermal energy (${k_{\textrm {B}}T}$). Such superparamagnetic MTJ (s-MTJ) cells, with an ${\mathcal {O}}$ (10 ns) retention time, need to be refreshed frequently. In the absence of data refresh (under attack conditions), the data they hold is thermally corrupted to a random state after an arbitrary but short amount of time. We leverage this property to devise a secure memory primitive and showcase its potential against cold boot and Boolean satisfiability (SAT) attacks. Further, the overheads for s-MTJ-based STT-MRAMs are shown to be promising for on-chip implementations. [ABSTRACT FROM AUTHOR]

Battery service time is a critical constraint on the availability and functionality of mobile devices. Equipping larger batteries may mitigate such deficiency yet it raises the challenges on thermal limit and physical size. Changing the battery chemistry is another solution, which however usually benefits the energy efficiency of only part of the applications, depending on their software behaviors. To address the challenges of battery energy efficiency and heat dissipation in limited physical space, we propose CAPMAN, a management framework that jointly optimizes the cooling and active power management in a smartphone, a typical mobile device, equipped with a hybrid battery pack. We establish the framework with three components. First, we abstract the correlation among the batteries, devices and software into a finite state machine model, whose state transitions can be triggered by actions like system calls and user activities. Second, we propose a battery scheduling algorithm that determines the more suitable battery for cooling/active power use, with respect to the dynamic software behaviors and their impact on the hardware states, based on a Markov decision process (MDP). Third, we design a facility for joint cooling and active power management by coordinating TECs and batteries. With the three major designs, CAPMAN realizes software defined management that schedules heterogeneous batteries and TEC cooling in a timely manner. In addition, CAPMAN provides an online algorithm with a proved O(1.05)-competitiveness performance. With a pair of big.LITTLE batteries, we prototype CAPMAN on multiple popular smartphones and a PYNQ development board. The evaluation with real-world workloads shows that compared to the current mainstream, CAPMAN can achieve 114 percent longer battery service time under skewed loads; compared to the state-of-the-practice baselines, CAPMAN shows 55 percent performance gain and 53 percent less energy use on average. Those results approve that big.LITTLE batteries with sophisticated software defined management is an effective way to prolong the battery service times on mobile devices. [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]