Analysis of heat and mass transfer enhancement in porous material subjected to electric fields (effects of particle sizes and layered arrangement)

Abstract

This research experimentally investigates the influences of electrical voltage, particle sizes and layer arrangement on the heat and mass transfer in porous packed bed subjected to electrohydrodynamic drying. The packed bed consists of a single and double layers of glass beads, water and air. Sizes of glass beads are 0.125 and 0.38 mm in diameter. Electric fields are applied in the range of 0–15 kV. Average velocity and temperature of hot airflow are controlled at 0.33 m/s and 60 °C, respectively. The results show that the convective heat transfer coefficient and drying rate are enhanced considerably with a Corona wind. In the single-layered case, due to effects of porosity, the packed bed containing small beads has capillary pressure higher than that with big beads, resulting in higher removal rate of water and higher rate of heat transfer. Considering the effect of capillary pressure difference, temperature distribution and removal rate of moisture in the double-layered case appear to be different than those observed in the single-layered case. Moreover, in the double-layered case, the fine-coarse packed bed gives drying rate higher than that given by the coarse–fine packed bed.