Abstract
Drying of moist porous media, such as food or pulp and paper, is an energy-intensive process. Innovative impinging jet nozzles, for instance, radial jet reattachment (RJR) and slot jet reattachment (SJR) nozzles, have been proved to be one of the efficient methods to enhance the drying rate compared to traditional in-line jet and slot jet nozzles. However, the heat and mass transfer in the region immediately underneath these nozzles are relatively inefficient. In this work, the performance of the SJR nozzle is improved by the application of electrical field, specifically, ionic wind generated in the region directly between the nozzle exit and the exposed surface of moist porous material. The numerical model is based on the coupled flow field generated by electrohydrodynamically (EHD) assisted SJR nozzle with the heat and mass transfer taking place within the moist porous media during the drying process. The simulation results show a significant secondary flow induced under the nozzle due to the ionic wind. Up to 40% drying rate enhancement has been achieved. However, the enhancement of drying rate diminishes as the air exit velocity exceeds a certain threshold. The simulation results illustrate the detailed fundamental understanding of this conjugated problem and provide a foundation for the enhancement of convective drying of moist porous materials.
