Power generation of annular thermoelectric generator with silicone polymer thermal conductive oil applied in automotive waste heat recovery

The annular thermoelectric generator (ATEG) matches the shape of the exhaust pipe. To improve the power generation efficiency of the ATEG in automobiles, a scheme is proposed to use a silicone polymer-based thermal conductive oil to transfer heat from the exhaust. Based on this concept, a new type of concentric tube heat exchanger is designed. A finite element model of the new system is established by considering temperature gradients, temperature dependence, and fluid resistance characteristics. Numerical simulations are performed to investigate the effects of exhaust parameters, thermal oil parameters, and heat exchanger structure on thermoelectric performance. The findings demonstrate a 15.2% increase in maximum output power of the new generator compared to a conventional ATEG, accompanied by a 19% decrease in the optimal thermoelectric module area. Furthermore, the net power first increases and then decreases with increasing thermal oil mass flow rate. The thermal oil mass flow rate can be adjusted in real-time based on fluctuations in exhaust parameters to achieve peak net output power. Finally, optimal fitting relationships between the heat exchanger dimensionless diameter and the total diameter, as well as between exhaust parameters and the optimal thermal oil mass flow rate, are obtained through parameter analysis and derivation.