Power Electronic (PE) will play an essential role in future drive concepts. Nowadays, mainly water/glycol-based cooling media are used to cool PE. Due to their high electrical conductivity (EC), water/glycol-based coo...Power Electronic (PE) will play an essential role in future drive concepts. Nowadays, mainly water/glycol-based cooling media are used to cool PE. Due to their high electrical conductivity (EC), water/glycol-based coolants cannot be used for direct cooling of the electrical components. Direct cooling concepts with dedicated transmission fluids show potential usage of fluid in direct contact with electrified parts. This results in special requirements for the fluids and materials. The aimed action as a coolant requires a defined measurement and characterization of fluid properties and heat transfer in order to assess the cooling ability of a fluid. The purpose of the work was to develop a new measurement setup based on the thermal transient method with which the thermal requirements of cooling fluids for a direct cooling concept can be assessed. With this method, relevant transmission fluids have been tested and the thermal performance compared to indirect cooling effect of water/glycol is discussed. The result of the work is that the measurement method is very well suited for the application-related evaluation of the fluids. Direct oil cooling with transmission fluids could increase heat transfer coefficient by a factor of 3 to 8, compared to the indirect cooing with water/glycol as cooling media.展开更多
In hot climates,the large amount of cooling load in electric vehicle(EV)results in a lot of battery energy consumption,leading the decrease of driving range.With the widespread application of windows in EV,the electro...In hot climates,the large amount of cooling load in electric vehicle(EV)results in a lot of battery energy consumption,leading the decrease of driving range.With the widespread application of windows in EV,the electrochromic glass(EC)shows great prospect in lowering the cooling load.However,researches on the application of EC in EV lack the consideration of both passive cooling measures and passenger comfort,which limits the further application of EC.In this paper,we proposed an idea combining the novel techniques of both electrochromism and radiative cooling.Computational fluid dynamics(CFD)is modeled to simulate the application of electrochromic and radiative cooling coupled smart windows in hot parking conditions,exploring the improvement effect of the window on the thermal environment,comfort and energy saving of the EV.The results indicate that,under the intense sunlight with an outdoor temperature of 33℃,activating the air conditioning to maintain an average interior temperature of 26℃,the coupled windows reduced the cooling capacity of the air conditioning by 762 W compared to regular windows,which can further increase the range of EV.Meanwhile,compared to simple electrochromic fully colored glass,the integration of radiative cooling technology can lower the window surface temperature by up to 10.7℃.Moreover,compared to regular windows,the coupled windows lowered the standard effective temperature(SET*)for passengers by approximately 7℃,significantly improving comfort.These research findings are expected to provide guidance for optimizing window design and enhancing the performance of EV.展开更多
High-energy-density lithium metal batteries(LMBs)are widely accepted as promising next-generation energy storage systems.However,the safety features of practical LMBs are rarely explored quantitatively.Herein,the ther...High-energy-density lithium metal batteries(LMBs)are widely accepted as promising next-generation energy storage systems.However,the safety features of practical LMBs are rarely explored quantitatively.Herein,the thermal runaway behaviors of a 3.26 Ah(343 Wh kg^(−1))Li|LiNi_(0.5)Co_(0.2)Mn_(0.3)O_(2)pouch cell in the whole life cycle are quantitatively investigated by extended volume-accelerating rate calorimetry and differential scanning calorimetry.By thermal failure analyses on pristine cell with fresh Li metal,activated cell with once plated dendrites,and 20-cycled cell with large quantities of dendrites and dead Li,dendrite-accelerated thermal runaway mechanisms including reaction sequence and heat release contribution are reached.Suppressing dendrite growth and reducing the reactivity between Li metal anode and electrolyte at high temperature are effective strategies to enhance the safety performance of LMBs.These findings can largely enhance the understanding on the thermal runaway behaviors of Li metal pouch cells in practical working conditions.展开更多
文摘Power Electronic (PE) will play an essential role in future drive concepts. Nowadays, mainly water/glycol-based cooling media are used to cool PE. Due to their high electrical conductivity (EC), water/glycol-based coolants cannot be used for direct cooling of the electrical components. Direct cooling concepts with dedicated transmission fluids show potential usage of fluid in direct contact with electrified parts. This results in special requirements for the fluids and materials. The aimed action as a coolant requires a defined measurement and characterization of fluid properties and heat transfer in order to assess the cooling ability of a fluid. The purpose of the work was to develop a new measurement setup based on the thermal transient method with which the thermal requirements of cooling fluids for a direct cooling concept can be assessed. With this method, relevant transmission fluids have been tested and the thermal performance compared to indirect cooling effect of water/glycol is discussed. The result of the work is that the measurement method is very well suited for the application-related evaluation of the fluids. Direct oil cooling with transmission fluids could increase heat transfer coefficient by a factor of 3 to 8, compared to the indirect cooing with water/glycol as cooling media.
基金supported by the National Natural Science Foundation of China(No.52130803,No.52394220)the New Cornerstone Science Foundation through the XPLORER PRIZE,Sichuan Province Innovative Talent Funding Project for Postdoctoral Fellows(BX202218)the China Postdoctoral Science Foundation(2023M732479)and Tsinghua University-Mercedes Benz Institute for Sustainable Mobility。
文摘In hot climates,the large amount of cooling load in electric vehicle(EV)results in a lot of battery energy consumption,leading the decrease of driving range.With the widespread application of windows in EV,the electrochromic glass(EC)shows great prospect in lowering the cooling load.However,researches on the application of EC in EV lack the consideration of both passive cooling measures and passenger comfort,which limits the further application of EC.In this paper,we proposed an idea combining the novel techniques of both electrochromism and radiative cooling.Computational fluid dynamics(CFD)is modeled to simulate the application of electrochromic and radiative cooling coupled smart windows in hot parking conditions,exploring the improvement effect of the window on the thermal environment,comfort and energy saving of the EV.The results indicate that,under the intense sunlight with an outdoor temperature of 33℃,activating the air conditioning to maintain an average interior temperature of 26℃,the coupled windows reduced the cooling capacity of the air conditioning by 762 W compared to regular windows,which can further increase the range of EV.Meanwhile,compared to simple electrochromic fully colored glass,the integration of radiative cooling technology can lower the window surface temperature by up to 10.7℃.Moreover,compared to regular windows,the coupled windows lowered the standard effective temperature(SET*)for passengers by approximately 7℃,significantly improving comfort.These research findings are expected to provide guidance for optimizing window design and enhancing the performance of EV.
基金Beijing Municipal Natural Science Foundation(Z200011)National Key Research and Development Program(2021YFB2500300)National Natural Science Foundation of China(22179070,22075029,U1932220),the“Shuimu Tsinghua Scholar Program of Tsinghua University”,and Mercedes-Benz AG.Xiang-Qun Xu and Xin-Bing Cheng contributed equally to this work.
文摘High-energy-density lithium metal batteries(LMBs)are widely accepted as promising next-generation energy storage systems.However,the safety features of practical LMBs are rarely explored quantitatively.Herein,the thermal runaway behaviors of a 3.26 Ah(343 Wh kg^(−1))Li|LiNi_(0.5)Co_(0.2)Mn_(0.3)O_(2)pouch cell in the whole life cycle are quantitatively investigated by extended volume-accelerating rate calorimetry and differential scanning calorimetry.By thermal failure analyses on pristine cell with fresh Li metal,activated cell with once plated dendrites,and 20-cycled cell with large quantities of dendrites and dead Li,dendrite-accelerated thermal runaway mechanisms including reaction sequence and heat release contribution are reached.Suppressing dendrite growth and reducing the reactivity between Li metal anode and electrolyte at high temperature are effective strategies to enhance the safety performance of LMBs.These findings can largely enhance the understanding on the thermal runaway behaviors of Li metal pouch cells in practical working conditions.
