Microdroplet capture by a tunable dielectrophoretic (DEP) filter*

Dielectrophoretic (DEP) collection of water droplets, 5 to a few tens of microns in diameter, transported in an air free-stream is investigated through a numerical simulation in view of applications in air purification technology. The droplet transport-dynamics are modelled as passive individual particles using a Lagrangian scheme that takes into account the interplay of inertia, viscous, DEP and random Brownian forces on the dispersed phase. The DEP filter is assumed to consist of an array of cylindrical model fibers, which also serve as electrodes where three-phase voltage is imposed. The filtering efficiency is determined through statistical analysis of the simulation results. The effects of the applied electric voltage on the filter efficiency are examined for different droplet diameters and inter-fiber distances and for a wide range of air velocity. The optimum frequencies at which the droplet capture efficiency attains its maximum value are also determined. It is shown that these frequencies are well correlated by a single dimensionless number representing the residence time of particles in the vicinity of the filter. Findings of the study leads to the design bases of active filtration systems for critical healthcare enclosures and advanced face masks.