Optimization of porous finned heat exchanger configuration using the comprehensive performance methodology

Abstract

This paper uses numerical simulations to investigate heat transfer in a heat exchanger with porous longitudinal fins and a counter-flow double tube. To improve the heat exchanger's overall heat transfer, porous media with uniform porosity is selected in longitudinal fins. To this end, the Darcy and Forchheimer models and the k-ɛ model are used to consider porous media effects and predict the turbulent flow structure. Furthermore, the energy equation was solved using the Local Thermal Non-Equilibrium method. According to the results, it has been noticed that there is a substantial increase in heat transfer upon decreasing the porosity. However, further decreases in porosity cause a growth in the porous material's resistance against fluid flow, which pushes it outside and prevents further increases. Finally, the heat exchanger's total performance variation shows that the optimum values of the permeability and porosity are equal to 10e-6 and 0.85, respectively. The results show the highest efficiency is achieved by a heat exchanger configuration associated with 40 porous fins, where the porous volume is considered as a constant portion of the total volume.