表面润湿性对水平管降液膜流型的影响

Effects of Surfaces Wettabilities on Horizontal Falling-Film Flow Pattern

降液膜的流动形态对水平管降膜蒸发器的强化传热过程具有十分重要的意义。本文构造了三种不同润湿性的表面,超亲水,亲水以及疏水,通过可视化实验和机理分析,研究了表面润湿性对降液膜管间流动的作用机理。结果表明,直列与错列柱状流的出现受到表面润湿性的影响。在亲水与超亲水表面只存在错列柱状流,而在疏水表面只存在直列柱状流。同时,错列柱状流的表面存在接触角上限,临界接触角为67°,直列柱状流的表面存在接触角下限,临界接触角为106°。

It is significant to study and regulate the inter-tube falling film flow pattern for the heat transfer of falling film devices.In this paper,the effect of surface wettability on the flow pattern is considered using three different tubes,super-hydrophilic and hydrophobic,includes hydrophilic tubes for comparison.Visual experiments and theoretical analysis are performed to study the effects of wettability on inter-tube flow pattern.The results show that staggered and inline column patterns are remarkably affected by the surface wettability.For super-hydrophilic and hydrophilic surfaces,only staggered column mode can be found for water.But for hydrophobic surfaces the inline column pattern occurs.In addition,there is a upper thread contact angle for staggered column mode,and the critical value is 67°.While for inline column mode,the minimum contact angle exists,and the critical angle is 106°.