Thermocapillary Phenomena and Performance Limitations of a Wickless Heat Pipe in Microgravity
Thermocapillary Phenomena and Performance Limitations of a Wickless Heat Pipe in Microgravity
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DOI：
10.1103/physrevlett.114.146105
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发表时间：
2015-04-07
影响因子：
8.6
通讯作者：
Zoldak, John
中科院分区：
文献类型：
--
作者：
Kundan, Akshay;Plawsky, Joel L.;Zoldak, John
观察到一种违反直觉的、由热毛细管引起的热管性能极限，这是当前热流体模型无法预测的。热管在许多物理限制下运行，包括毛细管，沸腾，声波和夹带限制，这些限制从根本上影响其性能。加热端附近的温度梯度可能高到足以产生显著的马兰戈尼力，从而阻止液体从冷端回流。这些力量被认为会加剧干燥条件，并迫使毛细血管过早达到极限。利用在国际空间站上用透明热管进行的实验的图像和热数据的组合，我们表明，在存在显著的马兰戈尼力的情况下，干燥不是限制性能的初始机制，但物理原因恰恰相反：热端被液体淹没。观察到的效应是毛细力和马兰戈尼力之间竞争的结果。驱油的温度特征与干油的温度特征几乎相同，如果不直接观察汽液界面，则很难进行诊断。
A counterintuitive, thermocapillary-induced limit to heat-pipe performance was observed that is not predicted by current thermal-fluid models. Heat pipes operate under a number of physical constraints including the capillary, boiling, sonic, and entrainment limits that fundamentally affect their performance. Temperature gradients near the heated end may be high enough to generate significant Marangoni forces that oppose the return flow of liquid from the cold end. These forces are believed to exacerbate dry out conditions and force the capillary limit to be reached prematurely. Using a combination of image and thermal data from experiments conducted on the International Space Station with a transparent heat pipe, we show that in the presence of significant Marangoni forces, dry out is not the initial mechanism limiting performance, but that the physical cause is exactly the opposite behavior: flooding of the hot end with liquid. The observed effect is a consequence of the competition between capillary and Marangoni-induced forces. The temperature signature of flooding is virtually identical to dry out, making diagnosis difficult without direct visual observation of the vapor-liquid interface.