泵辅助毛细相变回路的机理和实验研究

Aiming at solving problems including unsuccessful start-up, temperature oscillation and limited heat transfer capacity in capillary phase change loop, pump-assisted capillary phase change loop is proposed, which is an active-passive two phase circulation device utilizing both sensitive heat and latent heat of the working fluid to transfer heat. This system mainly utilizes evaporation of the working fluid to transfer heat. A mechanical pump is used for pumping the fluid to increase heat flux and transport distance. At the same time, the vapor phase in the compensation chamber of evaporator is eliminated to enhance operating stability of the system. In this project, a steady operating model of pump-assisted capillary phase change loop will be established to investigate its mechanism of heat transfer and flow. Physical mechanism and mathematical model reflecting temperature and pressure fluctuation caused by the vapor-liquid interface oscillation will be constructed to investigate the effect of eliminating vapor phase in the compensation chamber on stability of the system. An experimental prototype will be fabricated to study its operating characteristics including start-up from the cold state, transient state and steady state at different heat loads and to analyze the effects of the flow rate of the liquid, the species of working fluid, the liquid charge ratio and the heat sink temperature on its operating characteristics. Meantime, the experimental results will be used to check and modify the theoretical model. These investigations will be carried out to reveal the operating characteristic of the pump-assisted capillary phase change loop and to improve its heat transfer capacity and operating stability.

针对毛细相变回路（CPL，LHP等）启动困难、运行温度振荡和热传递能力有限等问题，提出一种主动与被动相结合，同时利用工质显热和潜热来传递热量的两相循环装置- - 泵辅助毛细相变回路。此系统主要利用工质相变传递热量，辅以泵增加工质循环量，提高热流密度和传输距离，同时，消除毛细相变回路蒸发器补偿腔内的蒸气相，增强系统运行的稳定性。本研究拟建立泵辅助毛细相变回路的稳态运行模型，研究系统的传热和流动特性；建立能够描述气液界面振荡而引起温度和压力波动的数学模型，考察补偿腔内消除蒸气相对系统稳定性的作用；研制泵辅助驱动的毛细相变回路实验装置和样机，研究其在不同热负荷下的启动特性以及稳态和瞬态运行特性，考察液体流速、工质种类、液体充灌率以及热沉温度对系统运行的影响，并对所建理论模型进行实验验证。通过以上研究，揭示泵辅助毛细相变回路的运行机理，提高两相循环系统的热传递能力和运行稳定性。

本项目提出泵辅助毛细相变回路，解决平面式环路热管小型化后容易出现启动失败、运行温度波动和热传输距离有限等不足。本研究重点分析了系统的热流和压降分布规律，并对系统的热工水力特性进行了计算。建立了系统的动态仿真模型，对系统在不同工况下的动态响应特性进行了预测。设计搭建了四套泵辅助毛细相变回路实验样机，实验探究了热负荷、冷媒温度和微泵功耗变化对系统性能的影响，并对装置性能进行了优化。此外，本研究针对采用不同循环工质的泵辅助毛细相变回路进行了实验研究。为了减小实验系统的质量，采用自主设计的离心微泵替代传统的磁力驱动齿轮泵，并实现了系统与微泵之间的匹配。研究结果发现，泵辅助毛细相变回路能够有效提高系统的运行稳定性，系统的传输距离和传递热流密度均较高。而且，由于分别设计的蒸气管路和液体管路，系统在传递较高热负荷时，所耗费的功耗较低。针对系统的不同运行工况条件，泵辅助毛细相变回路可以自动调节工作模式，启动和变负荷运行灵活。对于采用甲醇为工质的泵辅助毛细相变回路，在控制加热面温度80℃时，系统传递的最大热负荷为170W，对应热流密度为16.8W/cm2。对采用氨工质的实验系统，在控制加热面温度80℃时，系统传递的最大热负荷为340W，对应热流密度为33.4W/cm2。本研究提出的泵辅助毛细相变回路在满足高热流和长距离的输送条件下，系统运行稳定可靠。因此，本项目的研究工作能为未来星载热控领域和其他高热流散热场合提供一种高效可靠的散热手段。