Abstract
The multiphysics simulation methodology presented in this paper permits extension of computational fluid dynamics (CFD) simulations to account for electric power generation and its effect on the energy transport, the Seebeck voltage, the electrical currents in thermoelectric systems. The energy transport through Fourier, Peltier, Thomson and Joule mechanisms as a function of temperature and electrical current, and the electrical connection between thermoelectric modules, is modeled using subgrid CFD models which make the approach computational efficient and generic. This also provides a solution to the scale separation problem that arise in CFD analysis of thermoelectric heat exchangers and allows the thermoelectric models to be fully coupled with the energy transport in the CFD analysis. Model validation includes measurement of the relevant fluid dynamic properties (pressure and temperature distribution) and electric properties (current and voltage) for a turbulent flow inside a thermoelectric heat exchanger designed for automotive applications. Predictions of pressure and temperature drop in the system are accurate and the error in predicted current and voltage is less than 1.5% at all exhaust gas flow rates and temperatures studied which is considered very good. Simulation results confirm high computational efficiency and stable simulations with low increase in computational time compared to standard CFD heat-transfer simulations. Analysis of the results also reveals that even at the lowest heat transfer rate studied it is required to use a full two way coupling in the energy transport to accurately predict the electric power generation.
Highlights
Over the last few decades there has been a growing interest in using thermoelectric technology to increase the energy efficiency of various heat recovery systems
The results presented here are based on mesh independent simulations using the SST k-ω model the fluid dynamics and the thermoelectric performance obtained by solving Equations (1)–(11)
The heat transfer to the heat pipes and the thermoelectric modules field inside the heat exchanger in a horizontal plane in the middle section overlaid with streamlines causes the temperature to decrease in the exhaust gas flow, mainly in the center whereas the flow colored by the residence time
Summary
Over the last few decades there has been a growing interest in using thermoelectric technology to increase the energy efficiency of various heat recovery systems. Thereby, the EGR system allows significant reduction of nitrogen oxides (NOx ) in the combustion process but it produces waste energy. Part of this waste energy can be converted to useful electric energy using thermoelectric modules. Several experimental studies on thermoelectric systems for heat recuperation in automotive applications has been studied and presented in the literature [13,14,15,16,17,18,19,20]. The theoretical basis for modeling fluid dynamics and Energies 2020, 13, 4344; doi:10.3390/en13174344 www.mdpi.com/journal/energies
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