Structure Design And Performance Optimization Of Thermoelectric Devices In Service Environment

Thermoelectric devices directly convert heat energy into electric energy,which has the advantages of simple structure,no pollution and strong reliability,and has a very good development prospect.At present,the design,manufacture and application of thermoelectric devices are lack of comprehensive research.Studies and analyzes the structure design,welding process and working load to improve the quality of thermoelectric power devices.The research contents are as follows:（1）Physical model and temperature field analysis.The linear model,nonlinear model and simulation model of thermoelectric device are established,and the accuracy of the model is verified by experiments.By analyzing the advantages and disadvantages of the two physical models and the influencing factors of temperature field,the suitable environment of nonlinear model and linear model is obtained.（2）Structure design of thermoelectric devices.The Nelder-Mead method is used to design the structure of the single-stage thermoelectric power generation device.With the output power as the optimization objective,the output power could reach1.425 W after multi-parameter cooperative optimization.Taking the conversion efficiency as the optimization objective,the conversion efficiency can reach 6%after multi-parameter collaborative optimization.Taking output power and conversion efficiency as optimization objectives,a multi-objective optimization model was established.According to the importance of output power and conversion efficiency,choose the appropriate size parameters.It is found that the proportion of Bi₂Te₃increases when the hot face temperature T_hor the cold face temperature T_cdecreases,and the optimal interface temperature changes with the trend of the proportion of Bi₂Te₃.Combined with the boundary conditions,the heat transfer direction structure,variable section and section side-length ratio of the piecewise thermoelectric generation device were optimized,and the conversion efficiency reached 11.56%after the structure optimization.The proposed optimization method and conclusion can provide guidance for the geometric design of thermoelectric devices for large-scale application in the future.（3）Analysis of the influence of welding process in the manufacturing process of thermoelectric devices.The influence of two welding defects,wall hanging and cavity,on the quality of thermoelectric devices is analyzed from the aspects of power generation performance and reliability.By analyzing the phenomenon of hanging wall,it is found that it mainly affects the power generation performance of thermoelectric generation devices and reduces the maximum conversion efficiency by3.8%.The analysis of the cavity phenomenon shows that it mainly affects the reliability,which increases the maximum thermal stress.When the cavity appears inside the hot face,the thermal stress will be very large,which reduces the reliability of the thermoelectric device.The stress caused by void defects mainly occurs in the hot face,so it is necessary to pay attention to the hot face welding and improve the quality of hot face solder when designing the manufacturing process of thermoelectric power devices.The above research is of great significance to the manufacturing process design of thermoelectric devices and the selection of solder products.（4）Analysis of influencing factors of internal resistance and load design of application state of thermoelectric devices.In case of wide temperature domain and high thermoelectric arm,the influence of current on internal resistance is relatively large.In this case,the workload should be reasonably matched to make the thermoelectric power generation device in the optimal working state.When a thermoelectric power generation system works with 100 thermoelectric power generation devices,the maximum output power can be increased by 6 W and the maximum conversion efficiency can also be improved by optimizing the workload at400 K temperature difference.Due to the large number of thermoelectric devices working,it is very important to select the appropriate load to improve the performance of power generation.