Mathematical Multiphysical Modeling of Integrated Thermoelectric Devices

Thermoelectric devices have garnered attention for potential economic and environmental impacts when applied as waste heat recovery (WHR) systems. Scalability, steady-state and long- term operation, as well as compactness, are attractive features of TEDs. These characteristics are not enough to overcome the relatively low thermal conversion efficiency and electrical power output in comparison to conventional power generation systems. Consequentially, research has focused on determining optimal TED configurations that yield maximum performance for a given set of operating conditions. More often than not, these models are over-simplifications of physical systems that ignore critical physical phenomena and/or temperature dependency of material properties, namely in the modeling of the exhaust fluid ow and the developed temperature gradient across the device. In addition, such models are limited to one-o_ designs, providing little to no guidance on how to design a TED powered WHR system. To address the issue of modeling deficiencies, a robust, fully-coupled, thermal-fluid-electric mathematical model is introduced. This model simultaneously quantifies the thermal-fluid behavior of the exhaust gas, and the thermal-electric behavior of the heat exchanger and thermoelectric domains. The fluid behavior of the exhaust gas is modeled using empirical correlations. The thermal-fluid behavior of the exhaust gas is coupled to the thermal behavior of the heat exchanger via a control volume formulation of the Conservation of Energy equation. The thermal behavior of the heat exchanger and thermoelectric domain is modeled using a thermal resistance network coupled to the thermoelectric heat equation. The generated electric current develops implicitly with the temperature solution. The aforementioned system of equations includes temperature dependent material properties and is solved via an implicit iterative solution algorithm. This model is applied to a novel pin-fin integrated TED. Device performance based on operating conditions, device geometry and thermoelectric material geometry is determined. Using thermal-fluid data collected from Cummins ISL-powered transit buses as the inputs to the fluid domain, an exhaustive parametric study was conducted over all possible inputs and device configurations of a TED applied to WHR of the aforementioned engines