Heat transfer mechanism and characteristics of fluid film on multi-faceted surface under constant cross-flow conditions

•The Qsensible dominates the heat transfer mechanism due to relatively larger gap between the air inlet and the solid surface.•The Nusselt number is significantly higher on the multi-faceted surface and presents bidirectional characteristics.•The higher fluid film thickness does not improve heat transfer at the fluid film interface but its effect is more significant than the dimensionless interfacial velocity. The cooling of the fluid film on non-circular surfaces under cross-flow of air is investigated. The heat transfer mechanism and characteristics in enclosed space are not satisfactorily available and well understood. The multi-faceted surface is introduced to simulate the various surface prevalent in heat exchangers, such as the porous media and evaporator. The volume of fluid (VOF) method is used in the numerical investigation with a variation of liquid load to acquire the effect of the liquid to gas (L/G) ratio. The gap between the cross-flow air inlet and the fluid film is constant, but the fluid film surface is the main focus. The relatively larger gap between the air inlet and the fluid film surface results in the Qsensible dominating the heat transfer mechanism. Although the higher fluid film thickness does not improve the heat transfer, its effect is more significant than the dimensionless interfacial velocity, VI*, which is relatively higher on the multi-faceted surface. The Nusselt number is significantly higher on the multi-faceted surface. However, the multi-faceted surface generates flow separations and impairs the interfacial heat transfer. In addition, the Nusselt number is found to be bidirectional on the multi-faceted surface.