Comprehensive Numerical Modeling of Thermoelectric Devices Applied to Automotive Exhaust Gas Waste-Heat Recovery

Abstract

This study investigates using numerical methods the performance of thermoelectric devices (TEDs) integrated with heat exchangers and applied to automotive exhaust gas waste-heat recovery. Air as an exhaust gas and water as a cooling fluid are used. The effects of temperature-dependent properties of materials (TE elements, ceramic plates, connectors, insulation materials and fluids) and interface electrical and thermal contact resistances on TED’s performance are included in the analysis. Additionally, the fluid heat exchangers and the insulation materials are modeled using a porous media approach. The response of hot and cold fluid inlet temperatures (Thi, Tci) and flow rates, number of modules N, permeability of heat exchangers and TE materials type on TED’s hydro-thermoelectric characteristics is studied. An increase in either Thi or a decrease in Tci is resulted in an enhancement in TED’s performance. The addition of modules is shown a significant effect on heat input Qh and power output P0 predictions; however, a minimal impact on efficiency η is displayed with N. For instance, at Thi = 873.15 K and Tci = 353.15 K with clathrate n-Ba8Ga16Ge30 and p-PbTe material’s combination, compared to single module case, TED with four modules showed 3.77- and 3.7-fold increase in P0 and Qh, respectively. In the studied 1–4 modules range, the cold fluid flow rate and the permeability of heat exchangers are exhibited a negligible effect on TED’s P0 and η, whereas the hot fluid flow rate is shown an appreciable change in η values. Further, when Thi is less than 500 K, TED with bismuth-tellurides showed a higher performance when compared to the clathrates and lead-tellurides materials combination.