Due to the heat pipes’ transient conduction,phase change and fluid dynamics during cooling/heating with high frequency charging/discharging of batteries,it is crucial to investigate in depth the experimental dynamic ...Due to the heat pipes’ transient conduction,phase change and fluid dynamics during cooling/heating with high frequency charging/discharging of batteries,it is crucial to investigate in depth the experimental dynamic thermal characteristics in such complex heat transfer processes for more accurate thermal analysis and design of a BTMS. In this paper,the use of ultra?thin micro heat pipe(UMHP) for thermal management of a lithium?ion battery pack in EVs is explored by experiments to reveal the cooling/heating characteristics of the UMHP pack. The cooling performance is evaluated under di erent constant discharging and transient heat inputs conditions. And the heating e ciency is assessed under several sub?zero temperatures through heating films with/without UMHPs. Results show that the pro?posed UMHP BTMS with forced convection can keep the maximum temperature of the pack below 40 °C under 1 ~ 3 C discharging,and e ectively reduced the instant temperature increases and minimize the temperature fluctuation of the pack during transient federal urban driving schedule(FUDS) road conditions. Experimental data also indicate that heating films stuck on the fins of UMHPs brought about adequate high heating e ciency comparing with that stuck on the surface of cells under the same heating power,but has more convenient maintenance and less cost for the BTMS. The experimental dynamic temperature characteristics of UMHP which is found to be a high?e cient and low?energy consumption cooling/heating method for BTMSs,can be performed to guide thermal analysis and optimiza?tion of heat pipe BTMSs.展开更多
Electric vehicles(EV)played an important role fighting greenhouse gas emissions that contributed to global warming.The construction of the charging pile,which was called as the"gas station"of EV,developed ra...Electric vehicles(EV)played an important role fighting greenhouse gas emissions that contributed to global warming.The construction of the charging pile,which was called as the"gas station"of EV,developed rapidly.The charging speed of the charging piles was shorted rapidly,which was a challenge for the heat dissipation system of the charging pile.In order to reduce the operation temperature of the charging pile,this paper proposed a fin and ultra-thin heat pipes(UTHPs)hybrid heat dissipation system for the direct-current(DC)charging pile.The L-shaped ultra-thin flattened heat pipe with ultra-high thermal conductivity was adopted to reduce the spreading thermal resistance.ICEPAK software was used to simulate the temperature and flow profiles of the new design.And various factors that affected the heat dissipation performance of the system were explored.Simulation results showed that the system had excellent heat dissipation capacity and achieved good temperature uniformity.Rather than solely relied on the fans,this new design efficiently dissipated heat with a lower fan load and less energy consumption.展开更多
This paper considers the stationary flow of incompressible micropolar fluid through a thin cylindrical pipe governed by the pressure drop between pipe’s ends. Its goal is to investigate the influence of the viscosity...This paper considers the stationary flow of incompressible micropolar fluid through a thin cylindrical pipe governed by the pressure drop between pipe’s ends. Its goal is to investigate the influence of the viscosity coefficients on the effective flow. Depending on the magnitude of viscosity coefficients with respect to the pipe’s thickness, it derives different asymptotic models and discusses their properties.展开更多
Loop heat pipes(LHPs),as high-efficiency heat dissipation components,are considered to be superior thermal conductors beyond any known materials.To apply LHPs to mobile electronics,a small,thin and compact system need...Loop heat pipes(LHPs),as high-efficiency heat dissipation components,are considered to be superior thermal conductors beyond any known materials.To apply LHPs to mobile electronics,a small,thin and compact system needs to be designed.However,with the trend of miniaturization,the heat transfer performance of LHPs degrades rapidly due to the significant increase of working fluid backflow resistance.This work aims to propose an effective solution to this problem.In this work,the surface wettability gradient(SWG)is introduced into the ultra-thin LHP,and the influence of SWG on mass and heat transfer performance is studied comprehensively by using a transient three-dimensional numerical model.It is observed that the SWG can significantly increase the vapor-liquid circulation efficiency and improve heat transfer performance.Numerical experiments have been performed to compare the two kinds of LHPs with and without SWG.At the heat load of 4–6 W,the start-up time for LHP with SWG is shortened by 11.5%and the thermal resistance is reduced by about 44.3%,compared with the LHP without SWG.This work provides a solution for the performance-degradation problem caused by miniaturization,as a numerical reference for experiments.展开更多
Ultra-thin flattened heat pipe(UTHP) is an effective solution to solve the problem of high-power density heat dissipation in narrow space. The key factors that determine its thermal performance include: the shapes and...Ultra-thin flattened heat pipe(UTHP) is an effective solution to solve the problem of high-power density heat dissipation in narrow space. The key factors that determine its thermal performance include: the shapes and sizes of the UTHP, the wick structure, the type of working fluid and its filling ratio. The change in the filling ratio means not only a change in the amount of the working fluid, but also a change in the space distribution of the gas and liquid phases inside the heat pipe. Therefore, it is important to explore the effect of liquid filling ratio on the thermal performance of UTHP. It can provide effective guidance for the production of UTHP. In this work, experiments were conducted on four groups of UTHPs with different mesh wicks under a series of liquid filling ratios. The results demonstrate that the volume of the filling working fluid should account for 22%-37% of the total internal volume of the UTHP to avoid deterioration of heat transfer during the operation of the UTHP. In addition, a prediction model of the evaporator temperature has been established to provide guidance for the application of UTHPs.展开更多
基金Supported by National Natural Science Foundation of China(Grant No.51775193)Guangdong Provincial Science and Technology Planning Project of China(Grant Nos.2014B010125001,2014B010106002,2016A050503021)Guangzhou Municipal Science and Technology Planning Project of China(Grant No.201707020045)
文摘Due to the heat pipes’ transient conduction,phase change and fluid dynamics during cooling/heating with high frequency charging/discharging of batteries,it is crucial to investigate in depth the experimental dynamic thermal characteristics in such complex heat transfer processes for more accurate thermal analysis and design of a BTMS. In this paper,the use of ultra?thin micro heat pipe(UMHP) for thermal management of a lithium?ion battery pack in EVs is explored by experiments to reveal the cooling/heating characteristics of the UMHP pack. The cooling performance is evaluated under di erent constant discharging and transient heat inputs conditions. And the heating e ciency is assessed under several sub?zero temperatures through heating films with/without UMHPs. Results show that the pro?posed UMHP BTMS with forced convection can keep the maximum temperature of the pack below 40 °C under 1 ~ 3 C discharging,and e ectively reduced the instant temperature increases and minimize the temperature fluctuation of the pack during transient federal urban driving schedule(FUDS) road conditions. Experimental data also indicate that heating films stuck on the fins of UMHPs brought about adequate high heating e ciency comparing with that stuck on the surface of cells under the same heating power,but has more convenient maintenance and less cost for the BTMS. The experimental dynamic temperature characteristics of UMHP which is found to be a high?e cient and low?energy consumption cooling/heating method for BTMSs,can be performed to guide thermal analysis and optimiza?tion of heat pipe BTMSs.
基金This research was supported by the National Key Research and Development Plan(Key Special Project of Inter-governmental Na-tional Scientific and Technological Innovation Cooperation,Grant No.2019YFE0197500)Key Research and Development Projects of Hubei Province(Grant No.2020BAB129)+1 种基金the Scientific Research Foun-dation of Wuhan University of Technology(Grant Nos.40120237 and 40120551)the Fundamental Research Funds for the Central Uni-versities(Grant No.WUT:2021IVA037).
文摘Electric vehicles(EV)played an important role fighting greenhouse gas emissions that contributed to global warming.The construction of the charging pile,which was called as the"gas station"of EV,developed rapidly.The charging speed of the charging piles was shorted rapidly,which was a challenge for the heat dissipation system of the charging pile.In order to reduce the operation temperature of the charging pile,this paper proposed a fin and ultra-thin heat pipes(UTHPs)hybrid heat dissipation system for the direct-current(DC)charging pile.The L-shaped ultra-thin flattened heat pipe with ultra-high thermal conductivity was adopted to reduce the spreading thermal resistance.ICEPAK software was used to simulate the temperature and flow profiles of the new design.And various factors that affected the heat dissipation performance of the system were explored.Simulation results showed that the system had excellent heat dissipation capacity and achieved good temperature uniformity.Rather than solely relied on the fans,this new design efficiently dissipated heat with a lower fan load and less energy consumption.
基金supported by the Ministry of Science, Education and Sports, Republic of Croatia (03703727872797)
文摘This paper considers the stationary flow of incompressible micropolar fluid through a thin cylindrical pipe governed by the pressure drop between pipe’s ends. Its goal is to investigate the influence of the viscosity coefficients on the effective flow. Depending on the magnitude of viscosity coefficients with respect to the pipe’s thickness, it derives different asymptotic models and discusses their properties.
基金financial supports from the Science and Technology Innovation Commission of Shenzhen(Grant No.JCYJ20190809154007586)National Key Research and Development Program of China(Grant No.2017YFE0120800)+1 种基金National Natural Science Foundation of China(Grant No.U20A20241 and No.51702277)Science and Technology Development Fund of the Macao Special Administrative Region(Grant No.FDCT/013/2017/AMJ)。
文摘Loop heat pipes(LHPs),as high-efficiency heat dissipation components,are considered to be superior thermal conductors beyond any known materials.To apply LHPs to mobile electronics,a small,thin and compact system needs to be designed.However,with the trend of miniaturization,the heat transfer performance of LHPs degrades rapidly due to the significant increase of working fluid backflow resistance.This work aims to propose an effective solution to this problem.In this work,the surface wettability gradient(SWG)is introduced into the ultra-thin LHP,and the influence of SWG on mass and heat transfer performance is studied comprehensively by using a transient three-dimensional numerical model.It is observed that the SWG can significantly increase the vapor-liquid circulation efficiency and improve heat transfer performance.Numerical experiments have been performed to compare the two kinds of LHPs with and without SWG.At the heat load of 4–6 W,the start-up time for LHP with SWG is shortened by 11.5%and the thermal resistance is reduced by about 44.3%,compared with the LHP without SWG.This work provides a solution for the performance-degradation problem caused by miniaturization,as a numerical reference for experiments.
基金National Key Research&Development Program of China(Grant No.2017YFB0406100)Guangzhou Municipal Science&Technology Program Project(Grant No.201802010013)。
文摘Ultra-thin flattened heat pipe(UTHP) is an effective solution to solve the problem of high-power density heat dissipation in narrow space. The key factors that determine its thermal performance include: the shapes and sizes of the UTHP, the wick structure, the type of working fluid and its filling ratio. The change in the filling ratio means not only a change in the amount of the working fluid, but also a change in the space distribution of the gas and liquid phases inside the heat pipe. Therefore, it is important to explore the effect of liquid filling ratio on the thermal performance of UTHP. It can provide effective guidance for the production of UTHP. In this work, experiments were conducted on four groups of UTHPs with different mesh wicks under a series of liquid filling ratios. The results demonstrate that the volume of the filling working fluid should account for 22%-37% of the total internal volume of the UTHP to avoid deterioration of heat transfer during the operation of the UTHP. In addition, a prediction model of the evaporator temperature has been established to provide guidance for the application of UTHPs.
