Optimization of multiple-emitter discharge electrode for electrohydrodynamic (EHD) drying

Abstract

Electrohydrodynamic (EHD) drying is a novel drying technology suitable for food materials with high moisture content. This research focuses on the design of multiple-emitter discharge electrodes by optimizing emitters' type and arrangement. Four types of emitters with different tip angles and two arrangements (square or chess grid) have been tested. Imaging of ionic wind distribution revealed that emitters made of construction nails and thin pins created the most diffuse ionization field and uniform exposure of material surface, which resulted in the best discharge stability. A multiple-emitter discharge electrode's drying efficiency was evaluated by drying rate and specific energy consumption (SEC). The smallest SEC of 107.19 kJ/kg was for the nail electrode with the square arrangement of emitters at 3.5 kV/cm electric field strength and a 2 cm gap between discharge and collecting electrodes. An increase of the electric field strength or the gap led to increased drying rate and SEC. The chess arrangement did not affect SEC but significantly reduced the drying rate. The results of this research are critical for the industrial scaling of EHD drying. • An approach for visualizing ionic wind jets in corona discharge was developed. • Emitter tip angle determines the distribution of the ionic wind and space charge. • The multiple-emitter discharge electrode was optimized for maximum drying rate and minimum energy consumption.