Study on the wettability and condensation heat transfer of sine-shaped micro-grooved surfaces
Study on the wettability and condensation heat transfer of sine-shaped micro-grooved surfaces
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正弦形微槽表面润湿性及冷凝传热研究
DOI：
10.1016/j.expthermflusci.2017.09.002
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发表时间：
2018-01-01
影响因子：
3.2
通讯作者：
Li, Xiang
中科院分区：
文献类型：
--
作者：
Qi, Baojin;Zhou, Jiasen;Li, Xiang
本研究采用干法刻蚀技术在铝表面上精密、光滑地制作出深度12~24微米、宽度30~60微米的正弦形微槽表面。对疏水改性后的微槽表面滴状冷凝的润湿性和换热特性进行了实验研究，并对微槽表面液滴的聚结和扫掠过程进行了动态分析。结果表明，微槽表面的润湿行为和换热特性呈各向异性，垂直方向的静态接触角明显大于平行方向的静态接触角，接触角滞后也有相同的趋势。在换热实验中，板材垂直放置，沟槽布置在垂直和水平两个位置。对于垂直沟槽表面，垂直沟槽强化了液滴的扫掠作用，使滴状冷凝的换热增加到30-50%。当高度与螺距之比A/P增大时，换热效果更佳。与垂直沟槽表面不同，水平沟槽表面的实验结果与光滑表面的实验结果相似。液滴的净力和滑动速度都随着液滴的增大而增大，在相同的A/P比下，较大的几何尺寸有利于液滴的下落，水平沟槽表面的滑动速度仅为光滑表面的60~70%，垂直沟槽表面的滑动速度可达光滑表面的1.2倍甚至更高。
In this study, sine-shaped micro-grooved surfaces with depth of 12-24 mu m and width of 30-60 mu m were precisely and smoothly fabricated using dry etching technique on aluminium surfaces. After hydrophobic modification, the wettability and the heat transfer characteristics of dropwise condensation on the micro-grooved surfaces were investigated experimentally, and the coalescence and sweeping processes of droplets on micro-grooved surfaces were dynamically analyzed. As the results show, the wetting behavior and heat transfer characteristics on the micro-grooved surfaces presented anisotropic characteristics, the static contact angle in perpendicular direction 91 was significantly larger than that in parallel direction OH, and same trends can also be observed for contact angle hysteresis. In heat transfer experiments, the plates were set vertically and the grooves were arranged in two positions, vertical and horizontal. For the vertically grooved surface, the sweeping effects of falling droplets were enhanced by the vertical grooves and the heat transfer during dropwise condensation was increased to 30-50%. Better heat transfer performance can be achieved when the ratio of height to pitch, A/P, increased. Different from vertical grooved surfaces, the experimental results obtained from horizontal grooved surfaces were similar to the results of smooth surface. Both net force and sliding velocity increased as droplets grew, and larger geometrical size was favorable to droplets falling for same ratio of A/P. The velocities of sliding down on horizontal grooved surface were only 60-70% of that on smooth surface, while the velocities of sliding down on vertical grooved surfaces can reach 1.2 times or higher than that on smooth surface.