疏水表面蒸汽滴状冷凝传热实验分析

Experimental Analysis on Dropwise Condensation of Steam on Hydrophobic Surfaces

为了深入考察竖直表面上滴状冷凝强化蒸汽冷凝传热过程的作用机理,设计了滴状冷凝（DWC）、膜状冷凝（FWC）两种冷凝形态的疏水和亲水竖直圆柱形表面,进行了实验研究。结果表明：在30 k Pa压力和相同过冷度的情况下,滴状冷凝传热量是膜状冷凝传热量的2~4倍。其主要原因是滴状冷凝时冷凝表面呈疏水性,使经过合并后的大液滴在形成连续的液膜前就从表面上脱落下来,蒸汽能够持续不断地与冷表面直接接触,其换热强度远远大于膜状冷凝。

In order to get a better understanding of the mechanism of heat transfer enhancement on vertical surface in dropwise condensation of steam, two kinds of vertical and cylindrical surfaces were designed and investigated, one of hydrophobic for dropwise condensation （DWC） and another of hydrophibic for filmwise condensation （FWC）. The experimental results indicated that under 30 kPa pressure and with the same degree of subcooling, the heat transfer coefficient of the dropwise condensation is 2-4 times than that of filmwise condensation. The main reason is the surface of hydrophobic at dropwise condensation, so that the drops after merging could fall off from the surface before forming a continuous film, thus the steam can continuously contact with the cold surface directly and its heat transfer intensity is far greater than that of the film condensation.