Numerical investigation and optimization of a hexagonal thermoelectric generator with diverging fins for exhaust waste heat recovery

Conventional thermoelectric generator (TEG) configurations suffer from the temperature drop of exhaust gas, resulting in a decrease in output power. To address this issue, diverging fins are introduced into a hexagonal TEG to enhance the heat transfer between exhaust gas and heat exchanger. Additionally, a corresponding numerical model is established to predict and optimize the output performance of the hexagonal TEG. The study indicates that, as the diverging angle, number, and height of diverging fins increase, both output power and pressure drop of the hexagonal TEG continuously increase, except for the pressure drop which decreases with the increase of fin height. To achieve maximum output power, the optimal values for fin height (h) and number (n) are determined to be 15 mm and 30, respectively. Moreover, regarding the diverging angle, the optimal value is related to the exhaust mass flow rate, and the optimal diverging angle is 0.2° when the flow rate is lower than 35 g/s. At an exhaust mass flow rate of 35 g/s and a temperature of 550 K, the optimal hexagonal TEG achieves an output power of 143.94 W, experiencing a 5.83 % improvement compared to the traditional structure. Meanwhile, the pressure drop is only 1.92 kPa, within the allowable range of the hexagonal TEG. This research provides new perspectives for enhancing the performance of TEGs by introducing diverging fins in heat exchangers.