Active vortex generation and enhanced heat transfer in a 3D minichannel by Onsager–Wien effect

Abstract

A 3D numerical analysis of conjugate heat transfer in a rectangular minichannel in the presence of vortices generated by electric field induced Onsager–Wien effect has been performed. Fully coupled governing equations for flow, heat transfer, electric potential and charge transport are solved using the finite-volume framework of OpenFOAM®. Present study proposes a novel approach to increase mixing and heat transfer in a minichannel using the vortices generated by Onsager–Wien effect. Effects of the flow Reynolds number Re and electric Reynolds number ReEL on the thermo-hydraulic performance of the minichannel have been analyzed. The Onsager–Wien effect produces small flow vortices in the vicinity of thin plate electrodes flushed to the top and bottom walls of the channel. These vortices enhance the fluid mixing, deplete the thermal boundary layer and increase the heat transfer. The Onsager–Wien effect produces stable and prominent vortex structures at low Reynolds numbers. Whereas, the inertial force begins to dominate at higher Re and the vortices get smeared in the positive flow direction. In general, the heat transfer enhancement is directly proportional to the electric Reynolds number ReEL. A maximum of 48.25% increase in mean Nusselt number is observed within the parameter space considered herein. Results of this study indicate that, thermal boundary layer depletion and mixing by electric-field-induced Onsager–Wien effect substantially enhances the heat transfer performance of a minichannel, with a trivial additional electric power consumption. Results of the present numerical study will serve as a benchmark to design minichannel heat sinks with enhanced heat transfer based on thermal boundary layer depletion by application of weak/medium electric fields.