A Reserch On Heat Pipe Based Thermoelectric Generator With Axial Cascading Thermoelectric Modules

Nowadays, China has the second largest number of vehicles in the world. According to the research and analysis, almost 40% power which is from oil is taken away by exhaust gas. Assuming that 10% power can be recovered and utilized, thirty-five million ton oil will be saved based on the data of vehicle number of china. That means the availability and efficiency of oil is promoted and the emission is reduced. Therefore the study of waste heat recovery equipment is significant for energy conservation and emission reduction of vehicles.For achieving the industrialization of thermoelectric generator in vehicles, several problems should be overcame such as the poor recovery efficiency, huge size thermoelectric generator and low efficiency thermoelectric generation. Based on the previous experience of researchers, the following factors lead to these problems. First is the high velocity and variety temperature of exhaust gas which make the power difficult to be obtained. For getting enough heat power, researchers have to enhance the size of heat exchanger. Second is the low efficiency of thermoelectric materials. To generate a property electrical power, a great number of thermoelectric modules is needed. That indirectly leads to enlarge the size of thermoelectric generator. For solving these problems, a high efficient generator which is based on heat pipe and an axial cascading thermoelectric modules design is developed. The main contributions can be summed up as follows.(1) In this paper, a multi-layer structure with vertically arranging thermoelectric modules is presented first. This design increases the number of thermoelectric modules in a limited area. Consequently, the thermoelectric generator will be quite small with a considerable efficiency.(2) Heat pipes with the features of super-conductio, isothermality and variability of heat flux density are applied in the heat exchanger for improving the low efficiency heat transfer problem.(3) According to the target HongQi H73.0, a cylinder design scheme is adopted and simulated. During the simulation velocity vector of gas flow, temperature field are analysis. Based on the analysis, the staggered arrangement of heat pipe in the heating plates is selected.(4) Based on the simulation of generator, the modeling approach of thermoelectric module is studied first. Then an annular thermoelectric module is presented for matching our thermoelectric generator. Different from common module, the annular module is consist of four small modules and every small module has individual output. This design makes more connection ways and restrains the effect of thermoelectric modules charging each other. Finally, a connection way between modules is carried out according to characteristics of the annular module.(5) The simulation of annular module provides necessary parameters for circuit design. According to these parameters, a H-bridge converter is designed here for fulfilling the function of buck and boost. After the processing of H-bridge converter, the electrical energy can be directly used for charging batteries and electronic equipments in a vehicle.(6) Based on the structure design and simulation, a prototype generator with axial cascading thermoelectric modules based on heat pipe is produced first. Then a test with similar conditions of simulation is carried out and a comparison with the other structures is also done.The study confirms that the heat pipe based thermoelectric generator with axial cascading thermoelectric modules proposed in this paper has reasonable structure, small size, large power generation amount, high efficiency and good versatility. It can be used for different kinds of engines and it also can be designed into different shapes for different vehicles according to their structures and available space.