Despite the ever-increasing demand of nanofillers for thermal enhancement of polymer composites with higher thermal conductivity and irregular geometry,nanomaterials like carbon nanotubes(CNTs)have been constrained by...Despite the ever-increasing demand of nanofillers for thermal enhancement of polymer composites with higher thermal conductivity and irregular geometry,nanomaterials like carbon nanotubes(CNTs)have been constrained by the nonuniform dispersion and difficulty in constructing effective three-dimensional(3D)conduction network with low loading and desired isotropic or anisotropic(specific preferred heat conduction)performances.Herein,we illustrated the in-situ construction of CNT based 3D heat conduction networks with different directional performances.First,to in-situ construct an isotropic percolated conduction network,with spherical cores as support materials,we developed a confined-growth technique for CNT-core sea urchin(CNTSU)materials.With 21.0 wt.%CNTSU loading,the thermal conductivity of composites reached 1.43±0.13 W/(m·K).Secondly,with aligned hexagonal boron nitride(hBN)as an anisotropic support,we constructed CNT-hBN aligned networks by in-situ CNT growth,which improved the utilization efficiency of high density hBN and reduced the thermal interface resistance between matrix and fillers.With~8.5 wt.%loading,the composites possess thermal conductivity up to 0.86±0.14 W/(m·K),374%of that for neat matrix.Due to the uniformity of CNTs in hBN network,the synergistic thermal enhancement from one-dimensional(1D)+two-dimensional(2D)hybrid materials becomes more distinct.Based on the detailed experimental evidence,the importance of purposeful production of a uniformly interconnected heat conduction 3D network with desired directional performance can be observed,particularly compared with the traditional direct-mixing method.This study opens new possibilities for the preparation of high-power-density electronics packaging and interfacial materials when both directional thermal performance and complex composite geometry are simultaneously required.展开更多
温度是影响动力电池性能的关键因素.高效热管理技术可有效控制动力电池温度和温差.本研究采用微通道热管阵列作为电池热管理系统的热传导元件,分析了其在高热功率密度下的传热性能,理论计算了其等效导热系数,优化分析了其槽道尺寸对流...温度是影响动力电池性能的关键因素.高效热管理技术可有效控制动力电池温度和温差.本研究采用微通道热管阵列作为电池热管理系统的热传导元件,分析了其在高热功率密度下的传热性能,理论计算了其等效导热系数,优化分析了其槽道尺寸对流动传热的影响,对比了其与主流散热技术的性能差异.研究发现,热功率密度为0.3658 W cm^-2时,强制风冷散热条件下,采用微通道热管阵列技术可维持热源处表面温度45℃以下,温差1.3℃以下,低于无微通道热管阵列导热情况下的温升15℃,温差3.8℃.随着热功率密度增大至0.9176 W cm^-2,微通道热管阵列的等效导热系数增大为6027 W m^-1K^-1,其热源处表面最大瞬态温差约2.75℃.增大槽道尺寸参数可进一步改善微通道热管阵列的导热系数,改善其传热性能,但对液体回流驱动力有一定影响.该阵列具有较好的动态工况热稳定性和低温快速加热能力.与烧结热管组的温度性能相比,微通道热管阵列组最大温度可降低15.1℃,表面温差降低14℃,具有显著降温和均温优势,表明微通道热管阵列在动力电池热管理系统中具有广泛应用前景.展开更多
The thermal management of battery systems is critical for maintaining the energy storage capacity,life span,and thermal safety of batteries used in electric vehicles,because the operating temperature is a key factor a...The thermal management of battery systems is critical for maintaining the energy storage capacity,life span,and thermal safety of batteries used in electric vehicles,because the operating temperature is a key factor affecting battery performance.Excessive temperature rises and large temperature differences accelerate the degradation rate of such batteries.Currently,the increasing demand for fast charging and special on-vehicle scenarios has increased the heat dissipation requirements of battery thermal management systems.To address this demand,this work proposes a novel micro heat pipe array(MHPA)for thermal management under a broadened research scope,including high heat generation rates,large tilt angles,mild vibration,and distributed heat generation conditions.The experimental results indicate that the temperature difference is maintained 3.44°C at a large heat generation of 50 W for a limited range of tilt angles.Furthermore,a mild vehicle vibra-tion condition was found to improve temperature uniformity by 3.3°C at a heat generation of 10 W.However,the use of distributed heat sources results in a temperature variation of 3.88°C,suggesting that the heat generation distribution needs to be considered in thermal analyses.Understanding the effects of these special battery-operating conditions on the MHPA could significantly contribute to the enhancement of heat transfer capability and temperature uniformity improvement of battery thermal management systems based on heat pipe technologies.This would facilitate the realization of meeting the higher requirements of future battery systems.展开更多
基金supported by the National Key R&D Program of China(Nos.2018YFA0208402 and 2020YFA0714700)the National Natural Science Foundation of China(Nos.52172060,51820105002,11634014,and 51372269),Magna International,and EPSRC project“Advanced Nanotube Application and Manufacturing(ANAM)Initiative”(No.EP/M015211/1).
文摘Despite the ever-increasing demand of nanofillers for thermal enhancement of polymer composites with higher thermal conductivity and irregular geometry,nanomaterials like carbon nanotubes(CNTs)have been constrained by the nonuniform dispersion and difficulty in constructing effective three-dimensional(3D)conduction network with low loading and desired isotropic or anisotropic(specific preferred heat conduction)performances.Herein,we illustrated the in-situ construction of CNT based 3D heat conduction networks with different directional performances.First,to in-situ construct an isotropic percolated conduction network,with spherical cores as support materials,we developed a confined-growth technique for CNT-core sea urchin(CNTSU)materials.With 21.0 wt.%CNTSU loading,the thermal conductivity of composites reached 1.43±0.13 W/(m·K).Secondly,with aligned hexagonal boron nitride(hBN)as an anisotropic support,we constructed CNT-hBN aligned networks by in-situ CNT growth,which improved the utilization efficiency of high density hBN and reduced the thermal interface resistance between matrix and fillers.With~8.5 wt.%loading,the composites possess thermal conductivity up to 0.86±0.14 W/(m·K),374%of that for neat matrix.Due to the uniformity of CNTs in hBN network,the synergistic thermal enhancement from one-dimensional(1D)+two-dimensional(2D)hybrid materials becomes more distinct.Based on the detailed experimental evidence,the importance of purposeful production of a uniformly interconnected heat conduction 3D network with desired directional performance can be observed,particularly compared with the traditional direct-mixing method.This study opens new possibilities for the preparation of high-power-density electronics packaging and interfacial materials when both directional thermal performance and complex composite geometry are simultaneously required.
文摘温度是影响动力电池性能的关键因素.高效热管理技术可有效控制动力电池温度和温差.本研究采用微通道热管阵列作为电池热管理系统的热传导元件,分析了其在高热功率密度下的传热性能,理论计算了其等效导热系数,优化分析了其槽道尺寸对流动传热的影响,对比了其与主流散热技术的性能差异.研究发现,热功率密度为0.3658 W cm^-2时,强制风冷散热条件下,采用微通道热管阵列技术可维持热源处表面温度45℃以下,温差1.3℃以下,低于无微通道热管阵列导热情况下的温升15℃,温差3.8℃.随着热功率密度增大至0.9176 W cm^-2,微通道热管阵列的等效导热系数增大为6027 W m^-1K^-1,其热源处表面最大瞬态温差约2.75℃.增大槽道尺寸参数可进一步改善微通道热管阵列的导热系数,改善其传热性能,但对液体回流驱动力有一定影响.该阵列具有较好的动态工况热稳定性和低温快速加热能力.与烧结热管组的温度性能相比,微通道热管阵列组最大温度可降低15.1℃,表面温差降低14℃,具有显著降温和均温优势,表明微通道热管阵列在动力电池热管理系统中具有广泛应用前景.
基金This work was supported by the National Natural Science Foundation of China(No.U1864212)by the State Key Laboratory of Automotive Safety and Energy(No.ZZ2019-051).
文摘The thermal management of battery systems is critical for maintaining the energy storage capacity,life span,and thermal safety of batteries used in electric vehicles,because the operating temperature is a key factor affecting battery performance.Excessive temperature rises and large temperature differences accelerate the degradation rate of such batteries.Currently,the increasing demand for fast charging and special on-vehicle scenarios has increased the heat dissipation requirements of battery thermal management systems.To address this demand,this work proposes a novel micro heat pipe array(MHPA)for thermal management under a broadened research scope,including high heat generation rates,large tilt angles,mild vibration,and distributed heat generation conditions.The experimental results indicate that the temperature difference is maintained 3.44°C at a large heat generation of 50 W for a limited range of tilt angles.Furthermore,a mild vehicle vibra-tion condition was found to improve temperature uniformity by 3.3°C at a heat generation of 10 W.However,the use of distributed heat sources results in a temperature variation of 3.88°C,suggesting that the heat generation distribution needs to be considered in thermal analyses.Understanding the effects of these special battery-operating conditions on the MHPA could significantly contribute to the enhancement of heat transfer capability and temperature uniformity improvement of battery thermal management systems based on heat pipe technologies.This would facilitate the realization of meeting the higher requirements of future battery systems.