Analytical and numerical investigation of heat transfer and entropy generation of stratified two-phase flow in mini-channel

In this study, developing and fully developed heat transfer and entropy generation are numerically and analytically studied in the stratified two-phase flow in a mini-channel. In the numerical study, the governing equations are solved by implementing a second order finite difference method based on the projection algorithm and the interface is reconstructed through the application of the volume of fluid method. The numerical study is carried out for two cases: one, a stratified air-water flow and the other, a stratified oil-water flow. Effects of several important parameters on the velocity and temperature fields and total entropy generation are studied. The study indicates that the total entropy generation for both cases becomes maximum at a specific Reynolds number. In the analytical investigation, the fully developed velocity and temperature profiles are derived and relations for the fully developed Nusselt numbers as well as the local entropy generation are obtained. In addition, the effects of existing parameters are studied in such a way that simplifies using the results of the analytical study by presenting generalized diagrams for the pressure gradient, interface height and Nusselt numbers in the fully developed region.