Numerical Study of Particle Collection by Single Water Droplets

Particle collection efficiencies of water droplets were calculated by considering thermophoresis, diffusiophoresis, inertial impaction, wake capture, and effects of drop deformation. The computations were carried out for a droplet temperature of 10 °C with saturated gas temperatures of 20, 35, 65, and 95 °C. The temperature, water vapor, and velocity distributions around the collector were determined by direct numerical integration of the appropriate governing partial differential equations using a convenient orthogonal grid generation technique. The investigation shows the following: deposition of fine particles can be significantly enhanced by phoretic forces; flux deposition of fine particles can be related to Reynolds number through the proportionality, Eflux ∝ Re-0.78; the flux deposition of fine particles on the rear of the collector is significant for low Reynolds numbers; wake capture is relatively insignificant; drop deformation can improve the collection of larger particles by inertial impaction and of smaller particles as a result of increased hydrodynamic effects on such particles.