Modeling of Heat Transfer in Nanoscale Multilayer Solid-State Structures

Modeling of heat transfer in nanoscale multilayer solid-state structures is presented in this article to seek a potential design of thermoelectric materials. The phonon radiative heat conduction equation is used to describe the heat transport behavior in nanoscale multilayer solid-state structures and the diffuse mismatch model is utilized to simulate the interface condition between two dissimilar materials. In this paper, the thermal conductivity of thin film superlattices, nano wire superlattices and nano tube superlattices were calculated. Then, size effects on the performance of thermoelectric micro coolers were examined in detail. The results show that the effective thermal conductivity of thermoelectric materials in superlattice structures decreases as the layer thickness decreases. In addition, the thermal conductivities of nano wire and nano tube superlattices are less than that of thin film superlattices when they have the same layer thickness. It is noted that the restriction on the radial direction not only decreases the thermal conductivity in radial direction but also in axial direction. Thus, nano wire and nano tube superlattices are potential materials for high performance thermoelectric devices.