交錯潤濕性表面於紅銅圓管表面之冷凝熱傳研究

Abstract

本研究以外直徑25mm的紅銅圓管作為熱傳介質，使用溶膠凝膠法及低表面能物質塗覆作為改質方法，並以模切膠帶作為遮罩製備出以超疏水表面為基底之異質潤濕性表面，於含不可凝結氣體之環境下探討其對冷凝熱傳之影響。改質表面之接觸角大於150ﾟ，未改質之紅銅表面經烘烤後接觸角約為100ﾟ，而改質條紋之寬度分別為1.5mm、2.5mm，4.5mm、5.5mm，未改質條紋寬度則固定在0.5mm。 實驗結果顯示改質均質超疏水表面在低過冷度時相較於未改質表面之冷凝熱傳係數有30%左右的成長，當過冷度大於4 K時，均質超疏水表面將出現浸潤轉變，此時冷凝熱傳係數與未改質表面相近。而當改質條紋為1.5mm，過冷度為9 K時，交錯潤濕性表面對於冷凝熱傳表現有較好的增強效果，然而當表面過冷度低時，交錯潤濕性表面之冷凝熱傳係數均不如均質超疏水表面。

This study investigated the effect of tube surfaces with superhydrophobicity-based interlaced wettability on steam–air mixture condensation. Experiments were conducted on various types of surface with different modified strip widths varied from 1.5mm to 0.55mm. The contact angle of the modified surface is about 150ﾟ, and the contact angle of the copper surface after heated is about 100ﾟ. The experimental results revealed that the condensation heat transfer coefficient on the homogeneous modified surface could be 30% higher than the plain copper surface when the wall subcooling is lower than 4 K. However, when the wall subcooling is higher than 4 K, the condensation heat transfer coefficient on the homogeneous modified surface is almost the same as the plain copper surface. When the wall subcooling is 9 K, the condensation heat transfer coefficient of interlaced wettability surface with modified strip width of 1.5mm is higher than the modified homogeneous surface. However, the condensation heat transfer performance cannot be improved by interlaced wettability surface when the wall subcooling is low.