【作者】 张鹏；

【导师】 辛公明；

【作者基本信息】 山东大学 ， 动力工程及工程热物理， 2019， 硕士

【摘要】 环路热管(Loop Heat Pipe,LHP)是一种高效的两相换热装置,因其独特的结构和性能优势逐渐成为高热流密度电子元器件散热的前沿技术。而随着环路热管的小型化发展,环路热管的热泄漏问题逐渐受到研究者们的重视。毛细芯是影响环路热管换热性能的关键部件,提供了蒸发换热表面和工质循环的驱动力。毛细芯连接蒸发器和补偿器,其有效导热系数的分布是决定环路热管热泄漏问题的关键因素。为降低通过毛细芯向补偿器的热泄漏,本论文基于平板型环路热管,研制了沿工质流动方向有效导热系数递变的功能梯度毛细芯,通过实验方法研究了毛细芯有效导热系数递变对毛细芯和环路热管性能的影响。主要研究内容包括:1.设计制备了一批沿工质流动方向有效导热系数递变的一体化功能梯度毛细芯,调整不同有效导热系数毛细芯层的厚度比,探索了以镍(Ni)和聚四氟乙烯(PTFE)为材料的毛细芯烧结工艺;2.对功能梯度毛细芯进行了基本参数和性能参数的实验表征。采用浸泡介质法测定了毛细芯的孔隙率均在48.64%左右;使用扫描电子显微镜观察了毛细芯的孔径结构和形态,并使用压汞法测量了 Ni毛细芯和PTFE毛细芯的孔径分布,结果显示Ni毛细芯孔径分布较为集中,而PTFE毛细芯表现出了典型的双孔径毛细芯的孔径分布特点;使用稳态法测量了毛细芯的有效导热系数,结果显示Ni毛细芯的有效导热系数较PTFE毛细芯有效导热系数大。传质抽吸实验结果表明当工质为无水乙醇时,Ni毛细芯有更好的抽吸传质性能,但功能梯度毛细芯的抽吸传质性能与毛细芯层厚比没有明显的线性关系。此外,功能梯度毛细芯的蒸发传热性能测试结果显示功能梯度毛细芯的蒸发传热性能好于单一有效导热系数毛细芯。3.设计了一种可拆卸替换毛细芯的环路热管蒸发器并制造了相应的环路热管,实验研究了不同功能梯度毛细芯对环路热管启动性能和变工况运行性能的影响。实验结果显示部分功能梯度毛细芯环路热管可以有效改善热泄漏问题,降低启动时间和系统的运行温度,并抑制环路热管的温度波动问题。更多还原

【Abstract】 Loop Heat Pipe(LHP),as an efficient two-phase heat exchanger,has gradually become a front technology for heat dissipation of electronic components with high heat flux because of its unique structure and performance advantages.With the development of miniaturization of loop heat pipe,the problem of heat leak of loop heat pipe has been paid more and more attention by researchers.The wick is a key component that affects the heat transfer performance of the loop heat pipe,providing the evaporation heat transfer surface and the driving force for the working fluid cycle,and connects the evaporator and the compensation chamber,whose effective thermal conductivity has an important influence on the heat leak problem of the loop heat pipe.In order to reduce the heat leak through the wick to the compensation chamber,a series of functional gradient wicks with progressive change of effective thermal conductivity along the direction of working fluid flow were developed in this study.The effects of progressive change of effective thermal conductivity of the wick on the performance of the wick and loop heat pipe were studied experimentally.The main work is as follows:1.A series of integrated Functional gradient wicks with progressive change of effective thermal conductivity along the direction of working fluid flow were designed and fabricated,while the thickness ratio of wicks with different effective thermal conductivity was different between wicks.The wick sintering process using nickel(Ni)and polytetrafluoroethylene(PTFE)as materials was explored.2.The basic parameters and performance parameters of the Functional gradient wicks were characterized experimentally.The results of immersion method showed that the porosities of the wicks were all about 48.64%.The pore structure and morphology of the wicks were observed by scanning electron microscope,and the pore radius distribution of nickel wick and PTFE wick were measured by mercury intrusion method.The results showed that nickel wick has a relatively uniform pore radius,while PTFE wick showed typical pore radius distribution of biporous wicks.The effective thermal conductivities of wicks were measured by steady state method,whose results showed that the effective thermal conductivity of nickel wick is larger than that of PTFE wick.The results of mass transfer experiment showed that nickel wick has better mass transfer performance,but the mass transfer performance of Functional gradient wicks has no linear relationship with the thickness ratio of wicks.In addition,the experimental results showed that the evaporative heat transfer performance of the Functional gradient wicks was better than that of the single effective thermal conductivity wicks.3.A loop heat pipe evaporator with detachable and replaceable wick was designed and the corresponding loop heat pipe was fabricated.The effects of different Functional gradient wicks on the starting performance of the loop heat pipe and the operational performance of the variable working conditions were studied experimentally.The experimental results showed that some loop heat pipes with Functional gradient wick can effectively improve the heat leak problem,reduce the startup time and the operating temperature of the system,and suppress the temperature fluctuation of the loop heat pipe.更多还原