Wettability, fluid distribution width, rivulet flow, vertical flat surface, liquid film
The performance of heat transfer in the processes of evaporation, absorption, distillation and even condensation is affected from the wetting behavior of the liquid film flow on the surface. The complete wetting of the surface is usually required while breaking of thin liquid film is to be avoided. Various experimental settings have been designed by several researchers to investigate the main parameters influencing the stability of the film. However, in order to generalize and properly scale the results, the appropriate dimension of the test section and its influences on the wetting behavior are still unresolved questions that need to be addressed. Three different fluid distribution widths, including 200, 100 and 33 mm, when the geometry of distribution hole, the distance between holes and vertical flat surface are fixed, are carried out. Pure water at ambient temperature is used as working fluid. The measurement is focused on the wettability hysteresis and the shape transition from film to rivulet when the water flow rate are increased or decreased for wetting and dewetting experiments. Visual data captured on the test section under various fluid distribution widths are collected and analyzed using image binarization method to quantify the wetted area. The relation between the wetted area with respect to film Reynolds number and Weber number respectively are presented. The results show that the fluid distribution width can influence the wetting ability. The amount of wetted area, which is used to identify the wetting ability, is quite stable for decreasing flow rates, thus delineating the hysteresis characteristics of the wetting behavior of this solid-liquid pair. In general, a longer distributor width seems to be associated to a lower wetting ability and a lower wetting hysteresis. However, the same observation could not be applied to the results extracted with a 33mm width.