Capture efficiency of trap impactors used with atomized water/air mixtures

Trap impactors are devices that take advantage of inertia to extract particles from air in a multiphase mixture. In this study, the collection efficiency of a trap impactor was analyzed experimentally to quantify the capability of extracting micron-sized water particles and depositing them inside a trap. The dimensions and operating conditions of the impactor were varied within a test matrix, which examined the influence of nozzle outlet diameters, trap diameters, and jet-to-plate distances. This parametric study enabled an examination of the influence of particle Stokes number, flow Reynolds number, and outlet geometry on effective particle capture. Across these data sets, maximum efficiencies between 80-90% were achieved. In contrast to previous studies, once maximum efficiency was reached, capture efficiency decreased with increasing Stokes numbers for Reynolds numbers exceeding 7000. The results indicate that there is an ideal operating zone, dependent on Stokes and Reynolds numbers, where particle capture is most efficient.