Effect of hot side structures on trade-off between thermal uniformity and performance of stationary diesel engine thermoelectric generator systems

Thermal uniformity and performance are two critical characteristics of thermoelectric generator systems (TGS), yet they usually involve a trade-off during the structural optimization. This work proposes two structural modifications for the hot side heat exchanger (HHE), encompassing trapezoidal fin-shape and inclined muffler wall configurations, to enhance the temperature uniformity of TGS while minimizing negative impacts on system performance compared to the original optimized structure. The combined effects of fin-cut height or inclination angle, along with distance between HHEs, are systematically investigated using a one-way coupled computational fluid dynamics and thermal resistance model. Accordingly, the trade-off between thermal uniformity and output power is quantitatively evaluated for these configurations. The results clarify that these modifications improve the temperature uniformity via reducing heat transfer concentration at the HHE's front region by redistributing the exhaust flow and heat transfer area. However, this achievement is accompanied by reductions in the HHE's heat absorption capability, thereby decreasing the electrical and net output power. Reducing the distance between HHEs is found to mitigate the power reduction and improve the trade-off for both structures. For the trapezoidal fin structure, the maximum temperature uniformity improvement reaches 92.71 % with a net power reduction of 23.2 %; whereas the inclined muffler wall structure achieves 93.33 % improvement with a lower power reduction of 19.71 %. The inclined muffler wall structure combined with smaller HHE distances demonstrates better effectiveness. This work provides practical design guidelines for developing cost-effective TGSs through simple HHE structural modifications while supporting future improvements in lifespan through enhanced thermal uniformity.