Modeling of film condensation flow in oval microchannels

A theoretical film condensation heat transfer model was developed for refrigerant flowing through oval-shaped microchannels in annular flow regime with laminar liquid film flowing along the channel walls. The model considered the effects of surface tension, disjoining pressure, interfacial shear stress and interfacial thermal resistance. Study was conducted for mass fluxes in a range of 300-1500 kg/(m2 s) with two refrigerants, R134a and R1234ze(E). The local heat transfer coefficient and circumferential mean heat transfer coefficient along the flow direction were obtained. The liquid film thickness profiles at different locations are presented. Due to the effect of surface tension, the liquid film accumulates towards the semi-circular corner. The circumferential mean heat transfer coefficient is very high after entering the channel inlet, decreases along the flow direction and reaches a constant value. R134a has a slightly higher circumferential mean heat transfer coefficient than that of R1234ze(E) due to its higher liquid conductivity.