Effect of droplet deformation on inertial and thermophoretic capture of particles

Falling droplets significantly deform during the wet deposition and wet scrubbing processes, which affects particle capture. On the basis of studies on the deformation of droplets falling at terminal velocity with typical diameters, the flow and the temperature fields around deformed and spherical droplets were simulated by large eddy simulation. The deposition behavior of particles with varying diameters was studied in both flow processes. The effect of droplet deformation on the inertial capture efficiency and thermophoretic efficiency of particles was analyzed. Inertial capture efficiency is enhanced by droplet deformation when Stokes number (St) > 0.4 and reduced when St < 0.4. The relative difference in the inertial capture efficiencies of the deformed and spherical droplets with the same equivalent diameter increases first and then decreases and converges as St increases. The aforementioned phenomenon is a result of a change in windward area, the shield effects of the boundary layer, and particle inertia. Thermophoretic efficiency is reduced by droplet deformation, but the decrement is independent of temperature difference. The difference in thermophoretic efficiencies is a consequence of the shift in superficial area and in the Nusselt number caused by droplet deformation. A methodology to predict capture efficiency of deformed droplet is established based on comparing the capture efficiencies of deformed and spherical droplets.