Electrohydrodynamic drying of multiple food products: Evaluating the potential of emitter-collector electrode configurations for upscaling

Abstract

Electrohydrodynamic (EHD) drying is a promising, non-thermal drying technology, based on ionic wind generation between an emitter and a collector electrode. This simulation-based study evaluates impact of various emitter-collector configurations for EHD drying in order to assess their potential towards industrial upscaling. The conventional wire-to-plate configuration, which creates impinging flow, is found not to be an optimal solution for EHD drying of multiple food products in a fast and uniform way. With a single wire (emitter), it is found that the products placed more downstream dry slower due to the progressive loading of the air with water vapor. With multiple emitters, up to a threefold increase in drying time of the food products is found, compared to a single wire. This increase is caused by the recirculation of most air. To avoid water vapor accumulation in the drying zone, a wire-to-mesh configuration is proposed. The mesh collector minimizes interference of neighboring airflows and avoids recirculation of moist air in the drying zone. As such, the wire-to mesh configuration provides more uniform drying between adjacent products, but also within a product, as it can dry from all its surfaces. An increase in emitter density for the wire-to-mesh configuration leads to an overall increase in air speed, but, surprisingly, not to increased product drying rates. The reason is that the high-speed EHD airflow is always generated very locally in the vicinity of the emitter and collector. Thereby the convective drying process is not affected so much by the emitter density.