EHD-enhanced drying of partially wetted glass beads

The enhancement of drying rate from partially wetted glass beads by electric field (corona wind) has been experimentally evaluated in this study. In addition, the enhancement of drying rate by air flow alone has been studied for a wide range of Reynolds numbers. A fine copper wire with a diameter of 0.5 mm was the emitting electrode. It was charged in direct current with either positive or negative polarities from the corona threshold voltage until the occurrence of sparkover. The water level inside the glass beads was maintained constant during each set of experiments. For each case a companion experiment was carried out simultaneously under the same ambient conditions but without the application of electric field or cross flow, the result of which is used as a basis in the evaluation of the drying enhancement using electric field and air flow. The weight loss of water as well as the ambient temperature and humidity were measured. Each experiment lasted for at least 5 h. The results show that electric field is effective in the enhancement of drying rate of partially wetted materials. However, its effectiveness gradually diminishes when water level in the material recedes further. A method to overcome this shortcoming of EHD-enhanced drying is proposed.