Theoretical Study Of Thermoelectric Generation System For Recovering Waste Heat From Vehicle Exhaust

Energy is the driving force of social development and the basic of source that human depend on for existence. With the rapid development of industrialization, energy demand is greatly increased. Our country is the largest automobile producer and consumer in the world, the car is very popular in our life and make us more convenient. However, there is only a small part of energy produced by fuel combustion used to drive the vehicle to run, and a part of the residual energy is taken away directly by engine exhaust, which resulting in huge energy waste and environmental pollution. Thermoelectric generation technology, which using Seebeck effect to convert heat energy directly into electric power, due to its special merits of quiet operation, light weight, and compact structure, and especially its promising applications to waste heat recovery, is becoming a noticeable research field.In this paper, thermoelectric generation technology is used to recover heat energy from vehicle exhaust. In order to solve the problem of low power output and conversion efficiency caused by the great heat loss between the hot side of the thermoelectric generator and exhaust, this paper proposed a thermoelectric generator which has a big endothermic area and a small exothermic area, and as the phase change is more stable and has low thermal resistance, the generator also has a phase change exchanger to provide stable heat source. By using Fortran computer programming, this paper established a mathematical model using automobile exhaust as heat source and calculated the performance of the thermoelectric generator. The results showed when there is same temperature of exhaust, the power output and conversion efficiency is higher when increasing the ratio of the endothermic and exothermic area. But with increasing of the exhaust temperature, the optimization effect gradually weakened, so different kinds of working liquid were chosen at different temperature to enhance heat transfer. Increasing exhaust flow also can enhance heat transfer, and the more the flow, the weaker the optimization effect. In addition, to investigate the effects of the thermoelectric module geometric parameters on the thermoelectric performances, a series numerical simulation were done. With the increase of generator length, the power output is increase at first and gradually decreased after reaching the maximum while the conversion efficiency is declining. And with the increase of condensation height, there was a maximum on power curve, the longer the length of the equipment, the shorter the optimal condensation height while the more the number of the evaporation tubes, the longer the optimal condensation height. And the higher the condensation height, the smaller the efficiency while the more the number of the tubes, the bigger the efficiency.Finally, based on the current theoretical inadequacies, recommendations for improvement are proposed and the follow-up studies of the subject project are suggested.