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Modeling and Analysis of Nanostructured Thermoelectric Power Generation and Cooling Systems

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Title: Modeling and Analysis of Nanostructured Thermoelectric Power Generation and Cooling Systems
Author: Rabari, Ronil
Department: School of Engineering
Program: Engineering
Advisor: Mahmud, Shohel
Abstract: This thesis is an investigation of heat transfer processes in nanostructured thermoelectric (TE) systems. TE systems include solid state thermoelectric generators (TEG) and thermoelectric coolers (TEC). Current TE systems exhibit low performance (i.e., thermal efficiency and Coefficient of Performance (COP)) compared to conventional energy conversion devices. The higher Figure-of-Merit nanostructured TE materials can increase the performance of TE systems. In this study, a mathematical model of a TE system was developed including the Seebeck, Peltier, and Thomson effects, Fourier heat conduction, Joule heat, and convection heat transfer. Numerical simulations were performed using the coupled TE constitutive equations. The simulated results were expressed as contours of temperature and electric potential and as streamlines of heat flow and electric current. The effective thermal conductivities, calculated using different transport property models, were used to investigate nanostructured TE systems. Additionally, Bismuth-Telluride based nanostructured TE materials were prepared using the solid state synthesis method. The study results report parameters which affect the thermal efficiency, COP, and entropy generation in nanostructured TEG and TEC systems. These parameters include the temperature difference, electric current, volume fraction of nanoparticles, and convection heat transfer coefficients at different locations: the side surfaces of TE legs; between the thermal source and the hot side of a TE system; and between the thermal sink and the cold side of a TE system. The results show a decrease in the thermal efficiency and COP of a TEG and TEC system, respectively, as the convection heat transfer coefficient increases. Nevertheless, a TEC system with a higher electric potential input increases the COP with an increase in the convection heat transfer coefficient. This study establishes that the heat conduction contribution to the total heat input for TEG and TEC systems should remain as low as possible for maximum system performance. The synthesized Bi2Te2.7Se0.3, using the indirect resistance heating method, exhibited low density which may have contributed to a higher electrical resistivity and a lower Seebeck coefficient. The macroscopic modeling of nanostructured TE systems performed in this thesis provided results which can be applied to the design of next generation thermal management and power generation solutions.
Date: 2015-10
Rights: Attribution-NonCommercial 2.5 Canada
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Attribution-NonCommercial 2.5 Canada Except where otherwise noted, this item's license is described as Attribution-NonCommercial 2.5 Canada