Multipin EHD dryer: Effect of electrode geometry on charge and mass transfer

ABSTRACT

Electrohydrodynamic (EHD) drying is considered as energy-efficient nonthermal technology suitable for dewatering of heat-sensitive materials. This technology relies on the ionic discharge from the vertical pin or fine horizontal wire, impinging wet material deposited on the plate electrode of opposite polarity. The critical issue for the scaling of EHD dryer is the geometry of a multipin/wire discharge and collecting electrodes, in particular the spacing between pins/wires and the gap between discharge electrode and material surface. This paper presents the results of experimental study and mathematical simulation of multipin discharge current to maximize total charge and mass transfer at the material surface. A mathematical model for discharge current based on Poisson’s and Warburg fundamental equations was developed and validated in experiments with multipin electrodes of different spacing (1, 2, 3, 4, and 6 cm) and gaps from 2 to 4 cm. It was demonstrated that linear relationship between total electric current and drying rate is valid for any spacing and any gap with the range from 2 to 4 cm. It was experimentally documented that the judiciously selected geometry of the multipin discharge electrode could mitigate adverse effect of interference between neighboring ionic jets and bring the concept of EHD dryer to industrial practice.

KEYWORDS:

• Charge
• corona discharge
• electric field
• ionic wind
• modeling
• transport property distribution
• Warburg law

Acknowledgments

Authors are grateful to Patrick Wells for the commitment to research work and thorough data collection.