Experiment on thermal uniformity and pressure drop of exhaust heat exchanger for automotive thermoelectric generator

The power generation of exhaust TEG (thermoelectric generator) depends on heat energy and thermoelectric conversion efficiency. High efficiency heat exchanger is necessary to increase the amount of heat energy extracted from exhaust gas. On one hand, heat transfer is coupled with pressure drop for typical heat exchanger; on the other hand, the muffler unavoidably leads exhaust to large pressure drop for noise reduction. The present work tried to conceptually combine exhaust heat exchanger with muffler in the form of 1-inlet 2-outlet, 2-inlet 2-outlet and the baseline empty cavity. A test bench was developed to compare thermal uniformity and pressure drop characteristics over multiple vehicle operating conditions. 1-Inlet 2-outlet increased hydraulic disturbance and enhanced heat transfer, resulting in the more uniform flow distribution and higher surface temperature than the other. However, the averaged surface temperature was less than 100 °C, significantly limiting thermoelectric conversion efficiency. The pressure drops of 1-inlet 2-outlet, 2-inlet 2-outlet were 165%, 318% more than that of empty cavity when inlet temperature was 100 °C and mass flow rate was 131 kg/h, and were 319%, 523% more than that of empty cavity when inlet temperature 400 °C and mass flow rate 156 kg/h.