平板型环路热管启动特性数值模拟  

Start-Up Characteristic Simulation of a Flat-Plat Loop Heat Pipe

作　　者：王迅[1] 胡启帆 Wang Xun;Hu Qifan(School of Mechanical Engineering,Tianjin University,Tianjin 300072,China)

机构地区：[1]天津大学机械工程学院,天津300072

出　　处：《天津大学学报（自然科学与工程技术版）》2021年第6期645-650,共6页Journal of Tianjin University：Science and Technology

摘　　要：针对目前电子设备日益轻薄化的特点,以结构厚度更小的铜-水链式平板型环路热管为研究对象,研究了不同热负荷、不同充液率、不同倾角对其启动特性的影响.基于VOF多相流模型和多孔介质模型建立了蒸发器与储液器内的气液两相传热传质三维非稳态模型,对其启动过程进行了数值模拟,对毛细芯内部相变过程以及蒸发器内具有代表性的点的状态进行了监测并分析.结果表明:环路热管启动过程中,蒸发器内部相变产生的气体有两次汇聚过程,一次发生在启动开始阶段,主要集中在以蒸汽槽道为中心的蒸发器前段下部,汇聚时间较短;二次汇聚发生在启动完成、热管稳定运行阶段,主要集中在蒸发器前段,所占体积较大且形状较为规则.热管启动过程中存在两次温升,分别以金属导热和沸腾传热为主要原因导致,后者导致的温升速率明显大于前者.随热负荷增大,启动时间缩短,启动温升增加,回流液体对蒸发器稳定运行温度影响减弱,蒸发器出口气含率提升16%.大充液率条件下,环路热管启动过程缩短37.2%,且稳定运行时出口蒸汽温度降低,蒸发器内部工质气液分布更为均匀,启动更为安全.倾角存在时,蒸发器各点稳定运行温度存在2 K左右温降,因此倾角存在可实现启动小幅优化.The chained loop heat pipe with flat evaporator which has a smaller structure thickness is more suitable for the present situation that electronic devices becoming thinner and thinner,so based on the volume of fluid(VOF)method and porous medium model,the article established a three-dimensional model of evaporator and compensation chamber of a copper-water chained loop heat pipe with flat evaporator,used FLUENT to simulate its start-up characteristics under different heat loads,filling ratios and inclinations,observed the process of phase transformation inside the capillary core and monitored the status points.The results show that during the start-up of loop heat pipe,there are two convergence processes of the gases generated inside the evaporator,one of which occurs at the beginning of the start-up,mainly concentrated at the lower part of the evaporator’s front section with the steam channel as the center in a short time,the secondary convergence occurs at the stable operation stage,which is mainly concentrated in the front section of the evaporator,occupies a large volume and has a regular shape.The heat conduction of metal and the boiling heat transfer lead to two temperature rise of the heat pipe,and the temperature rise rate of the latter is obviously higher.With the increase of heat loads,the loop heat pipe has a shorter start-up time,a higher temperature rise,the influence of reflux liquid on evaporator temperature is weakened,and the gas holdup of the outlet increased by 16%.With high filling ratio,the starting stage shortened 37.2%,the operating temperature at evaporator outlet decreased and the work fluid is more evenly distributed in the evaporator which can cause a much safer star-up.The inclination of evaporator can realize a small optimization and cause the operating temperature at each point of the loop heat pipe to reduce about 2 K.

关 键 词：平板型环路热管 数值模拟 启动特性 

分 类 号：TK124[动力工程及工程热物理—工程热物理]