Innovative design of an annular thermoelectric generator for enhanced automotive waste heat recovery

The annular thermoelectric generator (ATEG) gains significant attention in the automotive waste heat recovery field due to its compatibility with the exhaust pipe's shape. To address the performance deterioration issue due to the temperature drop, a novel annular thermoelectric module (ATEM) structure is proposed, in which the crosssectional area of the thermoelectric elements continuously increases along the direction of heat flow. To assess the performance and perform parameter optimizations, this work develops a three-dimensional, steady-state, and fluid-thermal-electric multiphysics numerical model of the entire ATEG. The length difference of thermoelectric elements in different columns (Delta L) is comprehensively optimized through numerical simulations, and the effects of exhaust temperature and velocity on the optimal Delta L value are studied. The results indicate that a great temperature drop exists inside the ATEM, suggesting the advantages and effectiveness of the proposed novel structure configuration for modules. The optimal Delta L value is not sensitive to the exhaust gas temperature and velocity, and when Delta L = 0.06 mm, the novel ATEG achieves the highest output performance, with an output power of 76.66 W and an output efficiency of 1.45 % at the exhaust gas temperature of 550 K and the exhaust gas velocity of 30 m/s. The power and efficiency experience an improvement of 8.97 % and 8.93 %, respectively, compared to the traditional structure. Additionally, the lower exhaust gas temperature and velocity contribute to a greater performance improvement for the novel ATEG. This ATEM structural design provides a new approach to enhance performance when encountering temperature drop issues.