Effect of structure parameters on the performance of an annular thermoelectric generator for automobile exhaust heat recovery

Abstract

Annular thermoelectric generators (ATEGs), matched well with the exhaust pipe in shape, were put forward to recover the exhaust heat from automobiles. To design efficient automotive exhaust ATEGs (AEATEGs), the effect of five structure parameters both considering the heat exchanger and the ATEG was examined based upon a constructed theoretical model. A temperature variation and temperature-dependent property were incorporated by the finite element method. Apart from two commonly adopted performance indicators, power and net power, another indicator, net power density, characterizing the power cost, was proposed. The power increases exponentially with cylinder diameter, while there exists an optimum cylinder diameter for the net power, with which the maximum arises and over which it reduces considerably to a negative value. With extending the heat exchanger length, the net power increases but at a decreasing rate, because the temperature difference between two sides of ATEGs is reduced along the flow direction and arranging ATEGs downstream reduces the temperature difference upstream. The leg height and central angle approximately have no effect on the maximum net power, about 122 W. AEATEGs with the leg height of 2 mm and central angle of 3.75° are recommended from the perspectives of power production and cost.