Optimum design of heat exchanging device for efficient heat absorption using high porosity metal foams

Abstract

The present research provides a numerical assessment of waste heat recovery system which contains high porosity metal foam that absorbs heat from the hot flue gases. Top wall of the heat exchanging device is designed as a sinusoidal corrugated/wavy wall. Three different wavelengths (Lw) of 39, 24.375 and 17.728 mm and three different wave amplitudes (a) of 0.5, 1.0 and 1.5 mm along with various heights of metallic foam of 0.25H, 0.5H and 0.75H are considered. Two different pore density of 20 and 40 with constant porosity of 0.937 are accomplished for the numerical investigation over wide range of fluid velocities. Local thermal equilibrium (LTE) and Darcy extended Forchheimer (DEF) models are employed at the metallic foam region; k-ε turbulence model is accomplished at free flow region of the channel. The heat dissipation rate at the cold wall increases significantly to a maximum height of 0.5H and increases with increasing wave amplitudes of the channel at the expense of pressure drop. On account of smaller wavelength and higher wave amplitude, the heat absorption rate is found to be 26.25% - 32% more than the straight channel with 25% filling rate of metallic foams in the range of fluid velocity considered.