【作者】 李欢；

【导师】 刘伟；

【作者基本信息】 华中科技大学 ， 工程热物理， 2011， 硕士

【摘要】 环路热管(Loop Heat Pipe,LHP)是一种利用毛细力驱动的热控制和热传输设备。它是近20年内发展起来的新技术,由于其具有传热量大、传输距离长、管路可弯曲、反重力能力强、无需运动部件、可靠性高等特点,广泛应用于航天器热控制和电子器件散热。环路热管由蒸发器,冷凝器,气体管路和液体管路组成,其中,蒸发器是整个环路热管的核心,它直接与热源相连接,利用其中的工质相变带走热源的热量,其设计结构直接决定了环路热管的运行情况。而位于蒸发器中的毛细芯,则是蒸发器中的核心部件,它为整个环路热管提供了毛细芯驱动力,其制作是整个环路热管中技术含量最高,过程最复杂的。本文在环路热管的上述两个方面进行研究:双孔径烧结型毛细芯的研制和具有二次毛细芯的环路热管系统实验。在烧结型毛细芯上,针对高热流密度情况下,单孔径毛细芯容易出现干烧,本文研究制作出双孔径毛细芯,通过对气相和液相的分离达到更好的性能。搭建了毛细芯制备台架,测量了毛细芯的孔隙率,并用经验公式计算了毛细芯的渗透率,使用扫描电子显微镜来观察毛细芯的孔径与孔径分布。结果表明,造孔剂含量为30%,5Mpa下加压成型,700℃烧结出的毛细芯,孔隙率为77.40%,渗透率为3.15×10-13m2,并具有足够的机械强度满足机械加工要求。在环路热管实验上,设计了具有二次毛细芯的平板式蒸发器,辅助主毛细芯抽吸液体,使用上面制作的双孔径毛细芯作为主毛细芯,以不锈钢丝网作为次毛细芯,使用甲醇作为工质,主要研究了环路热管的启动特性、变工况性能、温度波动情况和系统热阻。结果表明,具有二次毛细芯的环路热管具有良好的启动特性,热负荷从20W到100W均可以正常启动;在变工况工作条件,热负荷从20W到160W范围内变化,系统均可以稳定工作。环路热管在30W到90W的热负荷范围内,系统运行出现温度波动,在此区间外,系统温度无波动现象出现。系统在160W(热流密度16.6W/cm2)工作时,壁面温度为84.0℃,说明,将研制的双孔径毛细芯应用于环路热管,如果结构设计合理,完全可以满足高热流散热场合的要求。更多还原

【Abstract】 Loop heat pipe (LHP) is a capillary driven heat control and heat transfer device, a new technology developed from recent 20 years. Due to its high heat transfer capacity, long transfer distance, flexible tube, anti-gravity ability, non-movement part, and high reliability, loop heat pipe is widely applied to thermal control in spacecraft and electronic devices.Loop heat pipe consists of evaporator, condenser, vapor line and liquid line. The evaporator is the key component in LHP which is directly connected to heat source, it dissipates the waste heat by phase change of working fluid. The evaporator design fundamentally affects the operation of LHP. And the porous wick is the key part of evaporator, which provides the capillary force for the whole loop, so it is the most important yet most difficult component to fabricate in the LHP.In this thesis, fabrication of the biporous wick and experiment of LHP with secondary wick were carried out.With respect to the fabrication of wick, in high heat flux condition, the vapor and liquid flow rate are equally large in the evaporator. Due to the fine pore, monoporous wicks will produce high hydraulic resistance, which is one of the most important reasons causing dry-out in evaporator. In order to resolve this problem, the biporous wick was fabricated in this thesis, with two different kinds of pores allowing the wick to achieve a better performance through separation of liquid and vapor. The experimental setup for manufacturing porous wick was built, pore former was proportionally added into the nickel powder, two methods, cold-pressing sintering and direct loose sintering, was applied to fabricate porous wicks. Porosity was measured by Archimedes method, pore radius was observed by Electronic Scanning Microscope, and permeability of wicks was calculated by empirical equation. Result shows that wicks are successfully fabricated, the optimal wicks are found to be sintered at 700°C, using cold pressing sintering method, with pore former content 30% by volume; these wicks could reach the porosity of 77.40%, the permeability of 3.15×10-13m2, and have sufficient mechanical strength to meet the machining requirements. With regard to the experiment of LHP, the evaporator with secondary wick assisting primary wick pumping working fluid was designed, and the sintered biporous wick mentioned above was selected as the primary wick. The start-up characteristics, performance in variable working condition, temperature oscillation, and thermal resistance were investigated in the experiment. Results showed that the LHP with innovative structure had a very good start-up characteristics, the system could start up from 20 to 100W. In variable working condition, LHP can operate reliably from 20 to 160W. The temperature oscillations occurred mainly in the heat load between 30 to 90W. Under heat load of 160W(with heat flux of 16.6W/cm2), the evaporator wall temperature was 84.0°C. The biporous wick can be applied in the high heat flux condition.更多还原