Geometry Design And Optimized Of Segmented Thermoelectric Devices

Segmented thermoelectric device is a type of thermoelectric device that can effectively improve the conversion efficiency of the thermoelectric device.It adopts a method of combining the higher temperature range of ZT value of different thermoelectric materials to improve the thermoelectric conversion efficiency and the thermoelectric output power compared to the conventional single material thermoelectric device.In this thesis,the finite element analysis method is used for segmented thermoelectric devices,and the thermoelectric output performance,together with the reliability are carried out.The structural optimization design is explored,hoping to provide guidance for the improvement of thermoelectric performance and reliability of more thermoelectric devices.Firstly,the finite element analysis method is used to establish a thermal-electrical coupling and thermo-mechanical coupling model for medium-temperature conditions,which lays a theoretical foundation for improving the thermoelectric output performance of thermoelectric devices and reducing the thermal stress of thermoelectric devices.Secondly,the numerical simulation analysis of the segmented thermoelectric devices under medium temperature conditions was carried out by means of simulation analysis via COMSOL Multiphysics software.Mainly on the thermoelectric leg of different thermoelectric leg geometry under the steady state conditions,thickness of ceramic sheet,the performance of the segmented thermoelectric device were studied.The structure of the segmented thermoelectric device was analyzed.The performance comparison with a single material leg was made for design optimization.The results show that the geometry of the thermoelectric leg and the thickness of the ceramic plate have significant effects on the thermoelectric output performance.The optimized model dimensions are: 2 mm p-type thermoelectric leg in all 3 dimension size,and 2 mm high n-type leg with a equal size of 1.5 mm in both length and width,adhered on a ceramic plate thickness of 2 mm.The maximum conversion efficiency is 11.2% at a hot end temperature of 700 °C and a cold end temperature of 100 °C.Compared to a single material Half-Hesuler thermoelectric device,the conversion efficiency increased from 7.22% to 11.2%.Finally,with the COMSOL Multiphysics simulation analysis software,the thermal stress numerical simulation analysis of the segmented thermoelectric unicouple device under medium temperature conditions was carried out.The reliability analysis of the thermal stress of thermoelectric leg geometry,geometry and thickness of ceramic plates of different thermoelectric materials under segmental thermoelectric devices were studied.The analysis of the model along the edge thermal stress in the X and Y directions was made.The results show that the thermal stress of the segmented device is larger than that of the single material device.When the length of the thermoelectric leg of the segmented thermoelectric device is increased,and the ceramic piece with a suitable cross-sectional area(2.5 mm)and a larger thickness is selected,the thermal stress of the thermoelectric device can be effectively reduced.