红外热像法研究降膜流动

采用高精度红外热成像技术研究固体平壁上加热和冷却液膜流动性能，比较了不同加热强度下液膜表面的温度场特征以及加热温差对固壁上液体分布的影响。传递过程中，界面上浓度和温度变化引起的表面张力梯度，驱使低界面张力处的液体流向高界面张力处（Marangoni效应），从而造成了液体特殊的流动现象与分布特征。在受热/冷却降膜过程中，由于流速和传热的差异，液膜表面存在一定的温度梯度。横向的温度梯度远大于流动方向的温度梯度，引起的Marangoni效应会造成受热液膜收缩和冷却液膜扩展，从而明显地影响液膜的相界面积及其传递性能。

Thermal imaging study of falling liquid films

The characteristics of heated/cooled liquid films flowing over a vertical solid plate were experimentally investigated with a highly sensitive infrared camera，Therma CAM ™ SC3000 (FLIR Systems，Inc.，Portland，OR). For different heating conditions，the temperature profile of the falling liquid film over a heated/cooled solid plate and the effect of heating temperature difference on the liquid distribution were determined. By using the infrared camera，the film width and the interfacial transfer area could be conveniently obtained. It was found that the transverse temperature gradient was much larger than that in the streamwise direction，resulting in significant Marangoni effect that drove the liquid particles from hot (low surface tension) to cold points (high surface tension)，inducing novel shrinkage/expansion of the heated/cooled film. The lateral Marangoni effect could therefore strongly affect the interfacial area and thus the transfer process of falling liquid films.