Numerical analysis of liquid jet impingement cooling of a thermoelectric generator

Abstract

Designs of heat exchangers are quite often disconnected to the performance of thermoelectric generators (TEG). In this work, the TEG and the heat exchanger are numerical modelled simultaneously in a computational fluid dynamics (CFD) environment (OpenFOAM) to maximize the output power of the system while minimize the hydraulic power required. A preliminary work was done where the modelling of the heat exchanger, a single laminar slot jet, and the modelling of a 16 element TEG are validated. The considered heat exchanger is a laminar slot jet consists of a linear array of discrete heat sources which accord with the geometry of a thermoelectric generator. The considered 16 element TEG is modelled using the temperature dependent material properties which require a solution of a system of nonlinear differential equations, namely the conservation of energy and the conservation of electric current. The conjugate heat transfer OpenFOAM solver chtMultiRegionFoam is extended by an additional differential equation for the solid region to model the conservation of current. The conservation of energy is expanded by additional source terms based on Peltier/Thomson effect and Joule heat. To simplify the calculation, interface and 1D resistor load boundary conditions are developed and implemented. The heat exchanger and the TEG model, both, are validated by comparisons with measurements, where a good agreement is observed.

Variable temperature effects on TEG performance

“…The applied temperature difference onto the TEG to generate the heat flow (the temperature difference between the hot and cold sides) is essential for the performance of TEG. In the previous work, we have developed a numerical procedure [25,26] to solve the above equations, which has been validated for conditions, where temperature boundary conditions were spatially homogeneous on each sides. The present work aims to generate data for variable temperature distributions on the cold side of a TEG.…”

“…In our previous work, the development of a finite volume method based solver has been presented, relying on the general-purpose, open source C++ toolbox for field operation and manipulation (OpenFOAM) [24].This solver (tegFoam) [25] has also been applied to solve the conjugate heat transfer problem that emerges in the coupled treatment of the TEG with the cooling system [26], where a variable temperature field on the cold side of the TEG emerges.…”

“…Those computational results [26] could not be validated against experiments, since relevant measurements could not be found in the open literature, implying the need for such measurements. This need gave the main motivation of the present work.…”