Numerical modeling of turbulent flow in an annular heat exchanger partly filled with a porous substrate

Computations are performed for a turbulent flow with the modified K - epsilon model in a double- pipe heat exchanger with a porous substrate in the annular gap attached to the inner cylinder. A proposal model for approximating the Forchheimer terms in the equations of turbulent kinetic energy and dissipation is developed by time averaging the general macroscopic transport equations. Numerical predictions are obtained using a finite volume method to investigate the turbulent fluid flow and heat transfer characteristics. Parameters such as the Reynolds number, the porous layer thickness, the permeability, and the thermal conductivity ratio are varied to asses their effects. The results show that the permeability has a great influence on turbulence intensity that goes by a maximum value at a certain Darcy number, and the efficiency of the heat exchanger is noticeably improved for a highly conducting porous substrate.