Numerical investigation of heat transfer in three-fluid stratified flows

Heat transfer in three-fluid stratified flow with prescribed wall temperature is numerically investigated in this article. The level-set method is adopted to capture the two evolving interfaces. Numerical solution of the coupled governing equations within the framework of the finite volume method is employed. Verifications of the model are performed by comparison against exact solution for heat transfer in single fluid flow with prescribed wall temperature, i.e. by setting the three fluids to be identical in the current model. Then, the effects of We number, Fr number, fluid flow rate ratio, viscosity ratio and thermal conductivity ratio on velocity and temperature fields, and more importantly heat transfer quantified in terms of local Nusselt number (Nu_x), and Nusselt number at fully developed flow region (Nu_f), are studied. The results show the increase of flow rates for fluid 1 (located at the bottom of the channel) and fluid 2 (located at the top of the channel) changes Nu_f at the upper wall, Nu_fu, and lower wall, Nu_fl, in different manners. Increasing fluid 1 viscosity and thermal conductivity increase Nu_fu while decrease Nu_fl, respectively. Nu_fu decreases and Nu_fl increases with the increase of fluid 2 viscosity and thermal conductivity.