2018 Volume 35 Issue 4 Pages 331-
Two phase flow in micro channel has been of research interest recently due to its high heat and mass transfer rate, and in this study, experimental investigation is performed on the influence of wettability of the tube in slug flow. The liquid film thickness and flow behavior of water-air slug flow are investigated by using laser focus displacement meter (LFDM) and high-speed camera, respectively. Circular glass tubes with inner diameters of 0.76mm and 1mm are prepared to be hydrophilic or hydrophobic by applying surface chemical treatment (using chemical surfactant: piranha solution and toluene). The experimental results are compared and discussed to obtain the influence of wettability, and as a result, the liquid film thickness is found to be similar in hydrophobic and hydrophilic micro channels, which is compatible with theoretical analysis. However, the flow characteristics is influenced by wettability at low capillary number region, at which no liquid film exists. The critical capillary number for film deposition on the wall is influenced by the hydrophobicity of the tube, consequently, the critical capillary number is higher in a hydrophobic tube than that in hydrophilic one.
