Characterization and Measurement Method for Variable Physical Parameters of Thermoelectric Materials Based on Quasi Steady State Method

The characterization of physical parameters of thermoelectric (TE) materials are of great significance in the application, optimal design, fault diagnosis and other related research of TE modules (TEM). At present, most of the characterization methods of physical parameters of TE materials believe that the TE parameters are constant in the characterization process, ignoring the nonlinear relationship between TE parameters and temperature, and not considering the contact electrical and thermal resistance in the TEM comprehensively. To address these issues, this paper proposes a characterization method of TE material variable physical parameters based on quasi steady state method and TEM testing device, which can realize the accurate characterization of TE parameters. Firstly, a quasi steady state method is proposed to characterize the physical parameters of material. Based on the temperature distribution of the TE leg, a one-dimensional discrete division can be carried out in the height direction of the leg and the TE leg can be divided into multiple continuous units with equal temperature differences. The temperature, heat flux and height of the unit can be obtained by solving the second-order partial differential equation of the temperature distribution of the TE leg, and further calculation can be carried out to obtain the TE parameters. In order to verify the accuracy of the above theories, a single leg TEM was simulated by using the COMSOL Multiphysics software. The calculation results of the quasi steady state method were closer to the parameters provided by the manufacturer, with a maximum error of only 3.1%. Compared with the steady state method, it has a significant advantage in accuracy. On this basis, combined with the testing device of TEM, the variable physical properties of TE materials were characterized through experiments. The results showed that although the experiment temperature ranges of the steady state method and the quasi steady state method were consistent, according to the principle, the quasi steady-state method got the wider temperature characterization range of TE material. In terms of the accuracy, due to the fact that the steady-state method considers the average physical parameters, there is a larger difference between the results of the steady-state method and the manufacturer's parameters. While the maximum error of the quasi steady state method in characterizing material prameters is 4.3%, which has more advantages compared to the steady state method. The following conclusion can be drawn from the results: (1) The thermal and contact resistance of the device have a significant impact on the accuracy of the characterization results of material parameters. Both steady-state and quasi steady-state methods that consider thermal and contact resistance have significantly improved the accuracy of characterizing TE parameters. (2) The quasi steady state method can reduce the error caused by the average temperature taken by the steady state method on both sides of TEM, thus it has better accuracy and a wider range of characterization temperature. (3) Based on the quasi steady state method, the characterization of material prameters can be achieved by using the TEM testuing device, which enriches the functions of TEM testing devices and can reduce material testing equipment investment and testing costs. © 2024 China Machine Press. All rights reserved.