Entropy Generation Analysis on a Metal Foam in an Automotive Exhaust Line With Thermoelectric Generator

Abstract

This paper presents a numerical solution for the entropy generation analysis of a two-dimensional steady-state convective regime in an aluminum foam. The analysis specifically focuses on a parallel plate channel filled partially or totally with metal foam, which incorporates on the external surface a thermoelectric generator (TEG). Local thermal equilibrium hypothesis is considered in the investigation to model the behavior of the metal foam and heat transfer within the channel. An exhaust gas is considered a working fluid, and its thermophysical properties are the same as those of air. The independence of the properties from temperature is considered. An internal energy production is assumed inside the TEG. The governing equations related to the physical problem with metal foam, exhaust gas, and TEG are solved by ansys fluent code. The investigation is accomplished for different aluminum foam thicknesses with various mass flowrate of working fluid. In the analysis, different values of pore density and porosity are assigned to the aluminum foam. The first is with 5, 10, 20, and 40 PPI, the second is from 0.90 to 0.978. Entropy generation due to friction and thermal effects as well as total entropy generation are reported. For all pore density and porosity values, the total entropy generation presents an increase related to an increment in mass flowrate. Bejan number decreases with increment in dimensionless thickness and mass flowrate. It increases when the porosity value increases whereas at high mass flowrate and for assigned porosity the values present small difference for different pore density values.