微重力下微结构表面池沸腾气泡动力学研究

Pool Boiling Heat Transfer and Bubble Dynamics Over Micro-Pin-Finned Surface Under Microgravity

针对航天器中电子器件的高效冷却问题,本文通过千式腐蚀技术在单晶硅表面形成一种新的柱状微结构(PF50-120),通过控制加热电压方法,在北京落塔进行了持续3.6 s有效微重力时间的过冷FC-72池沸腾强化换热实验研究.同时.通过高速摄像对壁面气泡动力学行为进行观测分析,结果发现柱状微结构不仅可以有效增加核态沸腾汽化核心数目,而且其独立于重力作用的毛细作用力可以驱动新鲜液体不断向附着在壁面上的大气泡底部供应,在较高热流密度下,柱状微结构表面仍然可以维持稳定的核态池沸腾换热,相比于光滑表面,强化换热效果显著.

For high-efficiently solving the power dissipation problem of electronic components on the spacecraft, experiments were performed using micro-pin-finned structure as heater surface in subcooled nucleate pool boiling of FC-72 under microgravity condition utilizing the drop tower Beijing. Micro-pin-fins with the dimensions of 50 μm× 120 μm （thickness × height） were fabricated on the surface of square silicon by using the dry etching technique. The micro-pin-finned silicon chip was heated by means of controlling heating voltage for the desired heat flux. At the same time, video of the bubble behavior was obtained by using high speed camera. The results showed that micro-pin-fins can increase the effective nucleate boiling sites number and the heat transfer performance efficiently, which stems from the sufficient supply of fresh liquid to the heater surface due to the capillary force independent of gravity. The steady nucleate pool boiling heat transfer on micro-pin-finned surface can be obtained at high heat fluxes and is greatly enhanced compared with smooth surface in microgravity.