| Thermoelectric technology,which using thermoelectric power generation of semiconductor materials,turning the low quality of heat energy into high quality electrical energy,is the current hot issues in the application of international materials technology.At present,automotive internal combustion engine heat energy utilization rate is only between 30% ~ 40%,which can improve the fuel economy of the vehicle by recovering and utilizing the waste heat of the automobile engine.Therefore,thermoelectric technology has broad application prospects in the field of automotive energy saving and emission reduction.At present,the research of thermoelectric materials mainly focused on improving the ZT value of material and improving the high performance thermoelectric preparative technique,and the application of key technology in the field of automotive is also unusual.Few researches are the experimental study of big automotive companies,which lacks of the study about heat transfer mechanism.Few researches about general thermoelectric generator have been carried out in non-automobile filed,which is only in the step of preliminary modeling and formula derivation without validation.As a result,based on the internal heat transfer mechanism in the thermoelectric generator,the three-dimensional steady-state multi-physical field mathematical model of thermoelectric unit and the numerical model of automotive exhaust thermoelectric generator have been developed by theoretical analyzing the thermal resist model and the thermal transfer process.Meanwhile,the thermal transfer theory and the thermal resist distribution are validated by experiments.At last,a mature thermoelectric generator system,including thermoelectric modules,heat exchanger,cooling unit,structure suspension and clamping system,are constructed,bench test and real car tests are also carried out.The work of this paper can be divided into three parts.Firstly,from heat transfer law of the thermoelectric generator,the thermal model and thermal resist net under multi-conditions are constructed by theory modeling,computer simulation and experiment,the heat transfer law of thermoelectric generator and impacts that influence the thermoelectric generator are deduced.Meanwhile,based on the thermal resist model,the general thermoelectric three-dimensional multi-physics field numerical models are developed to compare the predicted data with theoretical analysis as well as experiment data.And the output characteristics of constant parameters variable parameters are compared.Secondly,the output characteristics and transient response characteristics of the thermoelectric generator are tested by experiments.Different contact media are chosen,to investigate the contact condition between the solid-solid coupling surface of thermoelectric modules and the cooling/heat sources,to analyze the influence of thermal resistance and thermal contact resistance on the output characteristics of thermoelectric modules.The thermal resist model is validated experimentally.Four different heat-dissipation types are compared,including air free convection,low velocity forced convection,high velocity forced convection and liquid-cooling.The thermoelectric internal heat transfer mechanism are tested by analyzing the effects of different thermoelectric generator.Thermoelectric generator open-circuit voltage and output power change a lot in different heat dissipation methods.In the method of free convection,thermoelectric components open-circuit voltage and output power are less than other three heat dissipation methods,and the performance of the thermoelectric generators achieve best in liquid-cooling method.As heat source temperature increases constantly,the cooling performance differences would fall,and free convection method cannot meet the cooling requirement.The ideal heat dissipation method is liquid-cooling.Lastly,taking the exhaust waste as heat source,liquid cooling as heat sink,the coupled temperature field,electric field and flow field automotive exhaust-based thermoelectric generator numerical model is developed,in order to the overall performance of the system.The heat transfer mechanism and overall performance are discussed in different boundary conditions in heat source and heat sink inlet.At last,automotive thermoelectric generator system is constructed,including highly efficient heat exchanger,cooling system,thermoelectric components and clamping devices.Meanwhile taking a cross country vehicle as a platform,a highly integrated “four-TEGs” thermoelectric generator system is developed,and corresponding bench tests,road tests and drum tests are conducted. |
