Review of Thermal Design of SiC Power Module for Motor Drive in Electrical Vehicle Application

In the current vehicle electric propulsion systems,the thermal design of power modules heavily relies on empirical knowledge,making it challenging to effectively optimize irregularly arranged Pinfin structures,thereby limiting their performance.This paper aims to review the underlying mechanisms of how irregularly arranged Pinfins influence the thermal characteristics of power modules and introduce collaborative thermal design with DC bus capacitor and motor.Literature considers chip size,placement,coolant flow direction with the goal of reducing thermal resistance of power modules,minimizing chip junction temperature differentials,and optimizing Pinfin layouts.In the first step,algorithms should efficiently generating numerous unique irregular Pinfin layouts to enhance optimization quality.The second step is to efficiently evaluate Pinfin layouts.Simulation accuracy and speed should be ensured to improve computational efficiency.Finally,to improve overall heat dissipation effectiveness,papers establish models for capacitors,motors,to aid collaborative Pinfin optimization.These research outcomes will provide essential support for future developments in high power density motor drive for vehicles.

SIMULATION IN THERMAL DESIGN FOR ELECTRONIC CONTROL UNIT OF ELECTRONIC UNIT PUMP

The high working junction temperature of power component is the most common reason of its failure. So the thermal design is of vital importance in electronic control unit （ECU） design. By means of circuit simulation, the thermal design of ECU for electronic unit pump （EUP） fuel system is applied. The power dissipation model of each power component in the ECU is created and simulated. According to the analyses of simulation results, the factors which affect the power dissipation of components are analyzed. Then the ways for reducing the power dissipation of power components are carried out. The power dissipation of power components at different engine state is calculated and analyzed. The maximal power dissipation of each power component in all possible engine state is also carried out based on these simulations. A cooling system is designed based on these studies. The tests show that the maximum total power dissipation of ECU drops from 43.2 W to 33.84 W after these simulations and optimizations. These applications of simulations in thermal design of ECU can greatly increase the quality of the design, save the design cost and shorten design time

Thermal Design and Optimization of Heat Pipe Radiator for Satellites

Satellite＇s thermal control subsystem （TCS） has to maintain components and structure within their specified temperature limits during satellite service life. TCS designers have to face the challenge of reducing both the weight of the system and required heater power while keeping components temperature within their design range. For a space based heat pipe radiator system, several researchers have published different approaches to reach such goal. This paper presents a thermal design and optimization of a heat pipe radiator applied to a practical engineering design application. For this study, a prospective communication satellite payload panel with applied passive thermal control techniques was considered. The thermal passive techniques used in this design mainly include multilayer insulation （MLI） blankets, optical solar reflectors （OSR）, selected thermal coatings, interface fillers and constant conductance heat pipes. The heat pipe network is comprised of some heat pipes embedded in the panel and some mounted on inner surface of the panel. Embedded heat pipes are placed under high heat dissipation equipments and their size is fixed; minimum weight of the radiator is achieved by a minimum weight of the mounted heat pipes. Hence, size of the mounted heat pipes is optimized. A thermal model was built and parameterized for transient thermal analysis and optimization. Temperature requirements of components in both worst case conditions （Hot case and cold case） were satisfied under optimal sizing of mounted heat pipes.

Thermal insulation design of subsea vertical X-mas tree

Temperature drop is commonly observed in subsea vertical X-mas trees during shutdown.The presence of a huge temperature difference between internal crude oil and external seawater can cause severe equipment degradation of the oil flow channel(e.g.,hydrate precipitation),which can block the oil flow channel and interrupt the production process.The most vulnerable parts of a subsea vertical X-mas tree tend to be components with high convective heat transfer rates,such as production modules and short joints.We proposed an innovative approach for the insulation design of underwater equipment under a shutdown condition.First,we obtained a heat transfer analysis of the tree under working conditions through computational fluid dynamics to ascertain the initial temperature condition for an unsteadystate analysis.Second,we investigated the unsteady heat transfer characteristics of the tree with an insulation layer in the shutdown state and derived the relationships between insulation duration and thickness by data analysis.We used data analysis to identify the relationship between insulation duration and thickness.Finally,we derived the empirical formula of insulation thickness for underwater equipment given the effect of environmental factors on the heat preservation effect.We performed the experiment with an oil pipeline,and the results showed that the internal oil of the equipment did not hydrate within 8 h under the shutdown condition with insulation layers.

Thermal Design of Power Transformers via CFD

At Siemens, an in-house CFD （computational fluid dynamics） code UniFlow is used to investigate fluid flow and heat transfer in oil-immersed and dry-type transformers, as well as transformer components like windings, cores, tank walls, and radiators. This paper outlines its physical models and numerical solution methods. Furthermore, for oil-immersed transformers, it presents an application to a HV （high voltage） winding in a traction transformer of locomotives, cooled by synthetic ester.

Numerical Investigations on Fluid Flow and Heat Transfer Characteristics of an Ultra-Thin Heat Pipe with Separated Wick Structures

Thermal and fluid-flow characteristics were numerically analyzed for ultra-thin heat pipes.Many studies have been conducted for ultra-thin heat pipes with a centered wick structure,but this study focused on separated wick structures to increase the evaporation/condensation surface areas within the heat pipe and to reduce the concentration of heat flux within the wick structure.A mathematical heat-pipe model was made in the threedimensional coordinate system,and the model consisted of three regions:a vapor channel,liquid-wick,and container wall regions.The conservation equations for mass,momentum,and energy were solved numerically with boundary conditions by using a code developed by one of the authors.The numerical results with the separated wick structures were compared with those with the centered,which confirmed the effectiveness of the separation of the wick structure.However,the effectiveness of the separation was affected by the position of the separated wick structure.A simple equation was presented to determine the optimum position of the separated wick structures.Numerical analyses were also conducted when the width of the heat pipe was increased with the cooled section,which clarified that the increase in the cooled-section width with the addition of wick structures wasmore effective than the increase in the cooled-section length.A 44%reduction in the total temperature difference of the heat pipe was obtained under the present numerical conditions.Furthermore,a comparison wasmade between experimental results and numerical results.

Evaporation Heat Transfer Characteristics from a Sintered Powder Wick Structure Sandwiched between Two Solid Walls

An ultra-thin flattened heat pipe has been developed with a centered wick structure.This structure is essential to make the heat pipe thinner.However,the centered wick structure reduces the evaporation and condensation surface areas of the wick structure because it is sandwiched between heat pipe walls.In this study,because detailed discussion has not been made,heat transfer experiments were conducted for the wick structure sandwiched between two solid walls.This study focused on the evaporation heat transfer characteristics from the sandwiched wick structure.The experiments were conducted with three wick structures,that is,strip-shaped sintered copper powders with thicknesses of 0.5,1.0,and 1.5 mm.Water was used as working fluid.The capillary pumping performance,that is,the liquid lifting velocities of the three wick structures were the same.The experimental results of the three wick structures were compared regarding the relation between the evaporation heat transfer rate and the superheat of the working fluid.The heat transfer experiments were also conducted when one of the solid walls was removed from the wick structure.It was confirmed that even if the wick structure was sandwiched between the solid walls,sufficient evaporation of the working fluid occurred from the thin sides of the wick structure.

Challenges and recent progress in thermal management with heat pipes for lithium-ion power batteries in electric vehicles

Electric vehicles(EVs)are globally undergoing rapid developments,and have great potentials to replace the traditional vehicles based on fossil fuels.Power-type lithium-ion batteries(LIBs)have been widely used for EVs,owing to high power densities,good charge/discharge stability,and long cycle life.The driving ranges and acceleration performances are gaining increasing concerns from customers,which depend highly on the power level of LIBs.With the increase in power outputs,rising heat generation significantly affects the battery performances,and in particular operation safety.Meanwhile,the cold-start performance is still an intractable problem under extreme conditions.These challenges put forward higher requirements for a dedicated battery thermal management system(BTMS).Compared to traditional BTMSs in EVs,the heat pipe-based BTMS has great application prospects owing to its compact structure,flexibility,low cost,and especially high thermal conductivity.Encompassing this topic,this review first introduces heat generation phenomena and temperature characteristics of LIBs.Multiple abuse conditions and thermal runaway issues are described afterward.Typical cooling and preheating methods for designing a BTMS are also discussed.More emphasis on this review is put on the use of various heat pipes for BTMSs to enhance the thermal performances of LIBs.For lack of wide application in actual EVs,more efforts should be made to extend the use of heat pipes for constructing an energy-efficient,cost-effective,and reliable BTMS to improve the performances and safety of EVs.

Thermal control system of Alpha Magnetic Spectrometer

Since its installation on the International Space Station(ISS)in mid-May 2011,the Alpha Magnetic Spectrometer(AMS)has spent over two years on orbit,fully operational,collecting an enormous amount of data including the temperatures from the on-board 1118 sensors for thermal control.A large database is continuously updated and analyzed to understand the thermal behavior of the experiment in the space environment and its interaction with the ISS.This paper specifies the design,building,analysis and testing of the thermal control system and its various components for an overview of the AMS thermal control system and its space environment.Also given are some examples of analysis and correlation of the space environmental and ISS parameters with the thermal behaviors of various AMS components.

Thermal analysis of LED lighting system with different fin heat sinks

This paper designs a 3 × 3 light emitting diode （LED） array with a total power of 9 W, presents a thermal analysis of plate fin, in-line and staggered pin fin heat sinks for a high power LED lighting system, and develops a 3D one-fourth finite element （FE） model to predict the system temperature distribution. Three kinds of heat sinks are compared under the same conditions. It is found that LED chip junction temperature is 48.978℃ when the fins of heat sink are aligned alternately.

Introducing Degree Days to Building Thermal Climatic Zoning in China

Building thermal climatic zoning is a key issue in building energy efficiency.Heating degree days(HDD) and cooling degree days(CDD) are often employed as indexes to represent the heating and cooling energy demand in climatic zoning.However,only using degree days may oversimplify the climatic zoning in regions with complex climatic conditions.In the present study,the application of degree days to current building thermal climatic zoning in China was assessed based on performance simulations.To investigate the key indexes for thermal climatic zoning,the climate characteristics of typical cities were analyzed and the relationships between the climate indexes and heating/cooling demand were obtained.The results reveal that the annual cumulative heating load had a linear correlation with HDD 18 only in regions with small differences in altitude.Therefore,HDD is unsuitable for representing the heating demand in regions with large differences in altitude.A comprehensive index(winter climatic severity index) should be employed instead of HDD,or complementary indexes(daily global solar radiation or altitude) could be used to further divide climate zones.In the current official climatic zoning,the base temperature of 26℃ for CDD is excessively high.The appropriate base temperature range is 18℃ to 22℃.This study provides a reference for selecting indexes to improve thermal climatic zoning in regions with similar climates.

A Review on Thermal Design of Liquid Droplet Radiator System

Liquid Droplet Radiator (LDR) system is regarded as a quite promising waste heat rejection system for aerospace engineering.A comprehensive review on the state-of-the-art of LDR system was carried out.The thermal design considerations of crucial components such as working fluid,droplet generator and collector,intermediate heat exchanger,circulating pump and return pipe were reviewed.The state-of-the-art of existing mathematical models of radiation and evaporation characteristics of droplet layer from literatures were summarized.Furthermore,thermal designs of three LDR systems were completed.The weight and required planform area between the rectangular and triangular LDR systems were respectively compared and the evaporation models for calculating the mass loss were evaluated.Based on the review,some prospective studies of LDR system were put forward in this paper.

Optimal design analysis for thermal performance of high power 2.5D package

Based on ANSYS and Icepak softwares, the numerical analysis method is used to build up the thermal analysis model of the 2.5D package, which contains a high power CPU chip. The focus of the research is on the determination of the contributing factors and their effects on the thermal resistance and heat distribution of the package. The parametric analysis illustrates that the substrate conductivity, TIM conductivity and fin height are more crucial for heat conduction in the package. Furthermore, these major parameters are compared and analyzed by orthogonal tests, and the optimal solution for 2.5D integration is proposed. The factors＇ influence patterns on thermal resistance, obtained in this article, could be utilized as a thermal design reference.

Thermal Analysis and Validation of GF-4 Remote Sensing Camera

The Chinese GF-4 satellite remote sensor is the highest spatial resolution among the civil satellite on the geosynchronous orbit, which carries on a camera with spatial resolution of 50 meter in the bands of visible and near infrared red and 400 meter in middle infrared red band. The thermal design of the spacecraft was challenging because the high resolution and the sensitivity requirement to achieve the desired scientific objectives. This paper presents the thermal analysis and test of the GF-4 in GEO orbit. The major findings of the analyses are the following. The GF-4 experiences complex, alternating external heat flux and faces direct sunlight in most of the orbital period. By applying a finite element model, the predicted temperature variation of the components remains in the desired temperature regime even in the extreme conditions. Comparing the thermal analysis results, the difference between the predicted and measured temperatures was less than 3°C for most of the components. The thermal control system functioned properly and the thermal model simulated the actual thermal design of GF-4. This thermal design method realizes the high efficiency and precision thermal control of the first high resolution geostationary orbit camera in China, which can provide reference for the high precision and stability thermal control of large aperture optical camera.

Thermal performance analysis of non-uniform height rectangular fin based on constructal theory and entransy theory

A model of non-uniform height rectangular fin, in which the variation of base's thickness and width are taken into account, is established in this paper. The dimensionless maximum thermal resistance(DMTR) and the dimensionless equivalent thermal resistance(DETR) defined based on the entransy dissipation rate(EDR) are taken as performance evaluation indexes. According to constructal theory, the variations of the two indexes with the geometric parameters of the fin are analyzed by using a finite-volume computational fluid dynamics code, the effects of the fin-material fraction on the two indexes are analyzed. It is found that the two indexes decrease monotonically as the ratio between the front height and the back height of the fin increases subjected to the non-uniform height rectangular fin. When the model is reduced to the uniform height fin, the two indexes increase first and then decrease with increase in the ratio between the height of the fin and the fin space. The fin-material fraction has no effect on the change rule of the two indexes with the ratio between the height of the fin and the fin space. The sensitivity of the DETR to the geometric parameters of the fin is higher than that of the DMTR to the geometric parameters. The results obtained herein can provide some theoretical support for the thermal design of rectangular fins.

面向可持续淡水供应的吸附式空气取水技术的研究进展与展望:材料、装置和系统

Establishing alternative methods for freshwater production is imperative to effectively alleviate global water scarcity,particularly in land-locked arid regions.In this context,extracting water from the ubiquitous atmospheric moisture is an ingenious strategy for decentralized freshwater production.Sorption-based atmospheric water harvesting(SAWH)shows strong potential for supplying liquid water in a portable and sustainable way even in desert environments.Herein,the latest progress in SAWH technology in terms of materials,devices,and systems is reviewed.Recent advances in sorbent materials with improved water uptake capacity and accelerated sorption–desorption kinetics,including physical sorbents,polymeric hydrogels,composite sorbents,and ionic solutions,are discussed.The thermal designs of SAWH devices for improving energy utilization efficiency,heat transfer,and mass transport are evaluated,and the development of representative SAWH prototypes is clarified in a chronological order.Thereafter,state-of-the-art operation patterns of SAWH systems,incorporating intermittent,daytime continuous and 24-hour continuous patterns,are examined.Furthermore,current challenges and future research goals of this cutting-edge field are outlined.This review highlights the irreplaceable role of heat and mass transfer enhancement and facile structural improvement for constructing high-yield water harvesters.