Numerical analysis of forced convection of high-temperature exhaust gas around a metal-foam wrapped cylinder

Abstract

Due to its high volumetric porosity and large specific surface area, open-cell metal foam has considerable advantages in compact heat exchangers for waste heat recovery system of internal combustion engines (ICEs). In order to simulate the forced convection around a metal foam-wrapped tube, a precise macroscopic model using the Darcy-Forchheimer-Brinkman momentum equation and the local thermal non-equilibrium energy equation has been established, and the heat transfer and pressure drop performance are investigated. Effects of key parameters, including porosity, pore density, foam thickness and Reynolds number are numerically studied and analyzed. It is found that the presence of a foam layer around the cylinder changes the flow structure, especially in the rear of the cylinder, and then influences the heat transfer and pressure field. A comparative study has been conducted between foam cylinders and a bare tube for various Reynolds number. The results indicate that, compared to a bare cylinder, the average Nusselt number of metal-foam wrapped cylinders can improve as much as 10 times at Re=1000 and 18 times approximately at Re=6000, which shows significant improvement in heat transfer performance.