Heat Transfer Enhancement of Ionic Wind Assisted Slot Jet Reattachment Nozzle: A Numerical Study

Abstract

Impinging jet nozzles are omnipresent in industrial applications. Innovative impinging jet nozzles, such as radial jet reattachment (RJR) and slot jet reattachment (SJR) nozzles, have been proven to be highly efficient tools to enhance heat and mass transfer, compared to traditional in-line jet and slot-jet nozzles. However, the heat and mass transfer in the region immediately underneath these reattachment nozzles are relatively inefficient. The ionic wind is a promising technique for heat transfer enhancement. The ionic flow is induced when free ions are accelerated by an electric field, and exchange momentum with neutral air molecules. In this numerical study, the performance of the SJR nozzle is improved by the application of an electric field, specifically, ionic wind, which is generated in the region directly between the nozzle and the exposed impingement surface. The two-dimensional numerical model is based on the flow field generated by an ionic wind-assisted SJR nozzle. The simulation results show a significant secondary flow induced under the nozzle, due to ionic wind. A significant enhancement of local and average heat transfer coefficients is achieved. The heat transfer increases with the applied potential and nozzle exit velocity. However, the SJR flow pattern is altered when the air exit velocity is below a certain threshold. The simulation results provide an in-depth understanding of the heat transfer characteristics under various operating conditions and pave the way for developing this novel impinging nozzle design.