PARTICLE COLLECTION PERFORMANCE OF IMPACTORS IN DIFFERENT GASES

The particle collection performance of round jet impactors was measured as a function of particle size, flow rate, impactor size, and gas viscosity. Two impactor sizes covering a flow rate between 8 and 18 liter/min and a particle size between 2.5 and 16.2 μm were evaluated. The effect of gas property on impactor performance was emphasized. Nitrous oxide, air, and argon were used to vary gas viscosity from 148 to 222 μP. The experimental results indicated that gas viscosity plays an important role in impactor performance, while gas density, which was varied from 1.20 to 1.96 g/liter, does not. The wall loss of particles was measured and compared to the impactor particle collection efficiency. The measured efficiency data were successfully correlated with the square root of the Stokes number. Existing impactor theories were compared to the measured data. © 1990.