System design in electrohydrodynamic (EHD) drying – Effect of geometry and relative humidity

Electrohydrodynamic (EHD) drying is an emerging technology applied in food drying, using corona wind generated by a strong electric field between an emitter and a collector electrode. A product placed on the collector electrode is dried by this wind. To predict wind velocity and power consumption in larger scale EHD dryers, it is important to understand which factors impact the generation of electric current and corona wind. The objective of this study is therefore to assess the electric current and corona wind speed as function of the electrode configuration and relative humidity using a combination of experiments and Multiphysics modelling. The electrode configuration varies by testing varying collector electrodes (i.e. plate vs. mesh with pores of 1.7 × 1.7 cm or with pores of 0.1 × 0.1 cm) and by varying the distance between the emitter and collector electrode between 1 and 4 cm. The most optimized electrode configuration creating a high electric current and ionic wind speed was the short electrode distance and an open mesh; this led to a geometric constant of 29.2 cm −1 and an onset voltage of 5.4 kV. The least optimized electrode configuration (large electrode distance, plate) led to a geometric constant of 1.2 cm −1 and an onset voltage of 8.4. The electric current and wind speed were not influenced significantly by varying relative humidity of the air from 20% to 70%. The experimental observations were adequately predicted by the Multiphysics model. Results of this study can be used to optimize energy use and effectiveness of EHD dryers in food drying processes.