The impact of the heat leakage through air gap on thermoelectric generator applied in engine waste heat recovery

Efforts to enhance the performance of thermoelectric generators (TEGs) in engine waste heat recovery have primarily focused on directly increasing energy conversion efficiency. Heat leakage can occur in many parts of a TEG. It is needed to develop a model to help researchers study this phenomenon and propose measures to reduce heat leakage. To address this gap, this study establishes and validates a computational fluid dynamic (CFD) and finite element (FE) coupled model based on a TEG prototype and its engine test bench. Unlike other models, this approach captures the intricate dynamics of heat propagation from the TEG via air gaps, encompassing conduction, convection, and radiation. Comprehensive analysis reveals that heat leakage accounts for approximately 11% of TEG power output loss. Ignoring the impact of heat leakage can lead to an overestimation of TEG power output. Key areas of heat leakage are identified, and numerical factors influencing this phenomenon are explored. Vertical TEG placement and optimal spacing between thermoelectric modules emerge as effective strategies for mitigating the impact of heat leakage on power output. Leveraging these insights, strategic thermoelectric module placement, vertical TEG orientation, and the application of thermal insulation materials to the heat exchanger are proposed as measures to enhance TEG power output by approximately 5%. The experimental and numerical results underscore the feasibility of optimizing TEGs from the perspective of heat leakage, a crucial aspect previously overlooked. These findings provide valuable insights for future TEG optimization endeavors, highlighting the importance of addressing heat leakage to maximize TEG performance.