Simulation And Optimization Of Heat Transfer Performance Of Cold And Hot End Of Automobile Exhaust Temperature Difference Generator

During the running of a car,about 40% of the energy is discharged into the atmosphere in the form of high-temperature exhaust gas,which not only brings about energy loss but also causes environmental thermal pollution.If the waste heat energy is used,it will play an important role in energy conservation and environmental protection,and it will have far-reaching significance for the country's sustainable development strategy.The automobile tail temperature difference power generation technology uses the Seebeck effect of thermoelectric power generation materials to convert the waste heat of automobile exhaust into electric energy,which is one of the research hotspots for the use of exhaust heat from automobile exhaust.The thermoelectric conversion efficiency of the vehicle tail temperature difference power generation device is mainly determined by the performance of the thermoelectric power generation material and the temperature difference between the hot and cold ends of the thermoelectric power generation device.This article is aimed at the hot and cold end of the automobile tail air temperature difference power generation system.For the thermoelectric generation and heat collection system,the heat collection performance of different types and different structural parameters of the collector is analyzed through numerical calculation.Aiming at the cold end of the thermoelectric power generation device,the hydrogen production from methanol reforming was proposed as the cooling method.The cooling performance was analyzed by numerical calculation and compared with other cooling methods.The main work and conclusions are as follows:Firstly,GT-Power software was used to simulate the engine,and the relevant parameters such as exhaust gas speed and temperature under different working conditions were obtained,and the three-dimensional physical model of different structural type collectors was established.Using Solid Works software,three-dimensional physical models of different structural collectors were established.Using CFD software for numerical calculations,and verifying the independence of the grid.The experimental data in the literature are cited,and the numerical calculation results are compared with the experimental results.The correctness of the model and the feasibility of the numerical calculation method applied to the optimization study of the thermoelectric generator collector are verified.Secondly,the heat collection performance of five kinds of collectors under different engine conditions and different fin spacings was analyzed by numerical calculation.The results show that the inner fins of the collectors play a role of spoiler and increase the heat transfer area,and enhance the heat transfer performance.The heat transfer capacity increases with the decrease of the fin spacing.The staggered collector has the best heat collection effect.The collector effect of the pyramid collector is slightly lower than that of the staggered collector.However,the surface temperature uniformity of the pyramid collector is the best and the pressure drop at the inlet and outlet is low.Considering the collector heat collection efficiency,surface temperature uniformity,inlet and outlet pressure drop,and structural complexity,the pyramidal collector with fin spacing of 8.5 mm has the best performance.Finally,the advantages and disadvantages of air-cooled,water-cooled,and liquefied natural gas cold energy systems as thermoelectric power generation units.A method of using a methanol reforming hydrogen production reaction system as a cooling method for a cold end of a power generation apparatus is proposed.The results show: When the wall temperature of the reactor is 473 K,the conversion of methanol is 70.8%,the mass fraction of hydrogen is 0.073,and the average internal temperature of the reactor is 350 K,which is conducive to the formation of the cold end of the thermoelectric generator.Under this operating condition,the output power of the thermoelectric power generation module with hydrogen reforming method for methanol reforming is about 1.92 W.The generated hydrogen can be used in hydrogen fuel cells.According to the hydrogen fuel cell efficiency of 40%,1 kg of hydrogen can produce approximately 13.2 k WH of electricity.