Numerical study of developing laminar mixed convection in a heated annular duct with temperature dependent properties

This study presents a numerical simulation of the 3-D laminar mixed convection between two concentric horizontal cylinders with physical properties which depend on temperature. The outer cylinder is subjected to an internal energy generated by the Joule effect whereas the inner cylinder is adiabatic. The flow and thermal fields are modeled by the continuity, momentum, and energy equations with appropriate initial and boundary conditions using a cylindrical co-ordinate system. The model equations are numerically solved by a finite volume method with a second order accurate spatiotemporal discretization. For the considered geometric, dynamic and thermal controlling parameters, it is found that the transverse flow is always the cause of the circumferential variation of the temperature and the physical properties of the fluid. The phenomenon of the temperature stratification is highlighted and the vortices obtained lead to an improvement in the heat transfer quantified by the increase in the number of Nusselt. The obtained axial Nusselt number increases with the increased of Grashof number which is proportional to the heat flux imposed at the surface of the outer cylinder.