突出气相压头的环路热管启动特性实验与可视化研究

本文提出并研究了一种突出气相压头的环路热管(LHP)。该环路热管将加热面与吸液芯分离,形成一个蒸发腔。工质在蒸发腔内发生相变,热管的整体结构设计突出了工质的气相压头。实验研究了不同的灌充率对启动特性的影响,结果表明:加热功率相同时(30 W),较高的灌充率会导致较高的运行温度,当灌充率分别为55%、60%和70%时,运行温度分别为101. 9℃、102. 4℃和107. 9℃,且当灌充率高于60%时会发生明显的温度振荡。在灌充率为55%时进行了蒸发器的可视化实验,观察到该类型热管产生相变的主要特征,即:液相工质的滴落蒸发,气液相界面沿着吸液芯表面向下移动,最后液滴落到加热底板上,气液两相界面的移动规律说明该环路热管独特的运行特点。将液体工质从开始滴落经蒸发到下一次开始滴落的时间定义为一个周期,实验测定了在加热功率为55 W时滴落蒸发过程的循环周期为120 s。

Experiment Study and Visualization of the Startup Characteristics of a Loop Heat Pipe Enhanced by the Pressure Head due to Evaporation

A new-type of loop heat pipe(LHP),which is enhanced by the pressure head due to evaporation,was proposed and studied.Its wick was separated from the heating surface and a steam chamber was formed in which the phase change of the working fluid occurs and the pressure head due to evaporation can be effectively used. In the experiment,different charging ratios were considered to explore the operation characteristic. Results showed that the temperature oscillation occurred when the charging ratio was high(60%). Furthermore,higher charging ratios resulted in higher operating temperatures;namely,101. 9 ℃,102. 4 ℃,and 107. 9 ℃ corresponding to 55%,60%,and 70% of charging ratio,respectively. In addition,the specific operating model,a dropping-evaporation process,was found through the visual observation of the evaporator when the charging ratio was 55%. The vapor-liquid interface moved downward on the surface of the wick and finally,the liquid dropped on the heating surface,illustrating the specific operation process for this kind of LHP. If the period is defined as the time needed to complete the dropping and evaporation cycle for the working fluid,the cycle time was 120 s when the head load was 55 W.