Thermal Performance Evaluation of a Double-Tube Heat Exchanger Partially Filled with Porous Media Under Turbulent Flow Regime

Turbulent flow and heat transfer in a counterflow double-tube heat exchanger partially filled with metal foam have been investigated numerically in the present study. The flow regime is considered to be turbulent in both the porous media and clear flow regions. Forchheimer-extended Darcy and local thermal equilibrium equations are utilized to simulate fluid flow and heat transfer inside porous layer. Also, a modified model is used to consider intra-pore level of turbulence within metal foam. Two different configurations of porous insert are considered in order to investigate the heat transfer enhancement and pressure drop, resulting from inserting porous media in double-tube heat exchangers. The effects of porous layer diameter, Darcy number and porous material thermal conductivity on the overall heat transfer coefficient of heat exchanger are investigated. The results exhibit the high amount of turbulent kinetic energy inside porous layer that supports the use of turbulence equations inside the porous region. Finally, a performance evaluation criterion is defined which enables one to establish the optimum porous media characteristics in double-tube heat exchangers in terms of thermal performance and pumping power.