Kundan Akshay, Nguyen Thao T T, Plawsky Joel L, Wayner Peter C, Chao David F, Sicker Ronald J
The Howard P. Isermann Department of Chemical and Biological Engineering, Rensselaer Polytechnic Institute, Troy, New York 12180, USA.
NASA Glenn Research Center Cleveland, Ohio 44135, USA.
Phys Rev Lett. 2017 Mar 3;118(9):094501. doi: 10.1103/PhysRevLett.118.094501.
A wickless heat pipe was operated on the International Space Station to provide a better understanding of how the microgravity environment might alter the physical and interfacial forces driving evaporation and condensation. Traditional heat pipes are divided into three zones: evaporation at the heated end, condensation at the cooled end, and intermediate or adiabatic in between. The microgravity experiments reported herein show that the situation may be dramatically more complicated. Beyond a threshold heat input, there was a transition from evaporation at the heated end to large-scale condensation, even as surface temperatures exceeded the boiling point by 160 K. The hotter the surface, the more vapor was condensed onto it. The condensation process at the heated end is initiated by thickness and temperature disturbances in the thin liquid film that wet the solid surface. Those disturbances effectively leave the vapor "superheated" in that region. Condensation is amplified and sustained by the high Marangoni stresses that exist near the heater and that drive liquid to cooler regions of the device.
一根无芯热管在国际空间站上运行，以更好地了解微重力环境如何改变驱动蒸发和冷凝的物理及界面力。传统热管分为三个区域：加热端的蒸发、冷却端的冷凝以及两者之间的中间或绝热区域。本文报道的微重力实验表明，情况可能要复杂得多。超过阈值热输入后，即使表面温度超过沸点160 K，也会从加热端的蒸发转变为大规模冷凝。表面越热，冷凝到其上的蒸汽就越多。加热端的冷凝过程由润湿固体表面的薄液膜中的厚度和温度扰动引发。这些扰动有效地使该区域的蒸汽“过热”。加热器附近存在的高马兰戈尼应力会放大并维持冷凝过程，该应力会将液体驱动到装置的较冷区域。
