Performance parameters enhancement of a thermoelectric generator by metal foam in exhaust automotive lines

In this work the effect of metal foam thickness inside an automotive exhaust gas line with external thermoelectric generators (TEGs) is numerically investigated. A two-dimensional steady state heat transfer problem in forced convective regime in a porous medium inside a channel is considered. The study allows to evaluate the effect of metal foam on the TEG performances for different foam thickness, porosity, pore density and mass flow rate of exhaust gas. The investigation is accomplished for several values of the aforementioned parameters. The results are presented in terms of pressure drop and temperature profiles. TEG efficiency and electric power are estimated and depicted in terms of the main parameters. The main findings show that the use of metal foams determines significant increase in wall temperatures of the channel. Consequently, improvements in the TEG efficiency are detected also for several metal foam thickness values. However, the increase in pressure drop is observed and this points out a decrease in the net useful power due to the increase in pumping power. Some optimal configurations with highest ratio between electric power and pumping power are detected with respect to mass flow rate, metal foam thickness, porosity and pore density values.