Effects of heat transfer characteristics between fluid channels and thermoelectric modules on optimal thermoelectric performance

Semiconductor thermoelectric generation technology has a promising application for waste heat recovery and is becoming a noticeable research field. This paper presents a mathematical thermoelectric generator (TEG) model applicable to engine exhaust gas heat recovery. This model considers the conduction along the heat exchanger and the contact thermal resistance of the exchanger plate between the fluid channel and the thermoelectric modules, which were neglected in a previous numerical analysis. Considering that there is an optimum module size corresponding to the maximum power output in a TEG system, the effects of heat transfer characteristics between the fluid channel and the thermoelectric modules on the optimal thermoelectric performance are investigated by using an engineering equation solver (EES) program. Numerical results show that there is a larger optimal area and a lower peak power when considering the conduction and contact thermal resistance factors mentioned above compared to traditional results, which are determined by considerably different factors such as internal heat transfer and temperature distributions. Moreover, an optimal thermal conductivity coefficient that corresponds to the peak power output exists when the conduction along the exchanger is considered. In the case when conduction along the exchanger is not considered, higher the thermal conductivity, the better is the thermoelectric performance. A thin-plate exchanger is recommended in the TEG system owing to its high power output. The optimal module area increases linearly, and the maximum power output exhibits an obvious decrease with an increase in the contact thermal resistance.