Simulation-based optimization of electrohydrodynamic drying of biological materials

Electrohydrodynamic (EHD) drying is an effective non-thermal drying technology. Here the dehydration rate of the food product is enhanced by invoking ionic wind via a high voltage difference between the emitter and collector electrodes. Among various conventional emitter-collector configurations used for EHD drying, the wire-to-mesh configuration has recently been found to be promising in terms of drying kinetics, drying uniformity and scalability, compared to the conventional wire-to-plate configuration. This study aims to further enhance the potential of this promising collector design for EHD drying, by providing a next step in improving the collector electrode, to speed up the drying rate and increase. Mechanistic modeling is used to build a more realistic model of the mesh collector than currently used. In the first part, the major driving force for EHD drying are gathered and discussed, as a basis for further model improvements and to get an increased insight in this promising but complex drying technology. In the second part of this computational-theoretical study, the impact of various mesh parameters (wire diameter, wire number and porosity) on the electric field intensity, the resulting Coulomb force on the air flow and the drying rate was explored. To identify tradeoffs between drying rate, energy consumption and fluid mechanic losses, an EHD performance number is introduced. This allows having a comprehensive evaluation of energy efficiency and drying effectiveness of different device designs. In the last part, a more optimal mesh configuration is proposed that improves the overall EHD drying performance number. This improvement was achieved by using a lower number of conducting wires. Their number was chosen in such a way that an intensification of the electric field was obtained, based on an in-depth analysis of the electrostatic conditions. With this optimal configuration, a similar drying rate was obtained, but the resulting energy consumption was reduced with almost a factor 10. This improved mesh collector design is an important step towards EHD drying devices that are scalable to industrial scale, which are sufficiently clean and efficient