Size Dependent On The Seebeck Coefficient Of Polycrystalline Thermoelectric Material And Optimal Design Of Segmented Thermoelectric Unicouples

Thermoelectric devices for its valuable advantages (such as, no pollution, no noise, no wear, small size, high reliability, high thermal-electric power conversion speed and a wide range of output power) attract the widespread attention of researchers. In those advantages which has an important influence on the thermoelectric device of factors including:the figure of merit thermoelectric materials (Seebeck coefficient, thermal conductivity, electrical conductivity related), the device geometry, the manufacturing process and the hot and cold side of thermoelectric cooling devices form. So the above factors on the development of thermoelectric devices became important issues. In this paper, Boltzmann transport theory and the commercial finite element software ANSYS have been used to study a part of research about the Seebeck coefficient of the grain size effect of polycrystal bulk thermoelectric materials and the structural optimization design thermoelectric devices, and then obtained some useful results.First, for the Seebeck coefficient of size effect of polycrystal bulk thermoelectric materials, through the microstructure material view to think about the grain boundary scattering of electrons, by solving the electron transport equations, we have developed the theoretical model of Seebeck coefficient of the size effect of polycrystal bulk thermoelectric materials. Then we learned the Seebeck coefficient of the grain size effect of polycrystal bulk thermoelectric materials, and then more research about the transmission rate, the temperature and the mean free path of electrons to the effect of the Seebeck coefficient has been studied. The results show that the theoretical model can predict grain size effect of Seebeck coefficient of the polycrystalline bulk thermoelectric materials, which are well agreement with experimental results. The transmission rate of electron, the temperature and the mean free path of electrons are also have obvious influence on the Seebeck coefficient of grain size effect.Second, the thermoelectric conversion efficiency of the device has been investigated by using ANSYS software, considering material properties dependent on the temperature, the finite element model of sub-thermocouple has been established. Further the analysis of the influence of the load resistance, the thermocouple leg length, the cross-sectional area, the segment ratio, the contact resistance and the contact resistance for the device conversion efficiency has been studied.In a word, in this thesis we studied the Seebeck coefficient of thermoelectric materials and thermoelectric devices for structural optimization, and which provided the thermoelectric materials and design of the corresponding means to the development of the thermoelectric materials and devices.