Thermal phenomena in electrohydrodynamic (EHD) drying

Abstract

In this work, we explored the effect of AC corona discharge on water evaporation in a strong electric field by using a multipin-dielectric-plate EHD system. Our experiments demonstrated that the AC corona discharge could produce a significant amount of heat because of the Joule and dielectric heating of the dielectric barrier. When the electric field strength was below the ionization point and current density did not exceed 1 mA/m2, the heating was not substantial. At the initial stage of corona discharge with the current density below 10 mA/m2, the cooling effect of evaporation compensated the Joule heating of the dielectric barrier, keeping wet material surface below wet-bulb temperature. With a current density above 10 mA/m2, the AC heating effect became dominant. At 40 kV applied voltage and current density of 38 mA/m2, the temperature of the dielectric increased from 22 °C to 25 °C and the material surface reached wet-bulb temperature. A theoretical model of the relationship between material temperature, electric field strength, discharge current and drying rate in EHD drying was developed and experimentally verified.