Isoaxial aerosol sampling: nondimensional representation of overall sampling efficiency

Abstract

Accurate aerosol measurements of ambient and industrial air environments are essential for the protection of human health. In this study, the overall aerosol sampling efficiency of a tubular thin-walled inlet, sampling isoaxially from environmental airflows, has been determined by a dynamic evaluation technique for various values of particle size, wind and inlet velocities, and inlet size. With the assumption of laminar flow, models developed from the results discriminate the dominant mechanisms that modify the sample properties during sampling and evaluate quantitatively the possible sampling errors for relatively wide ranges of sampling conditions. For Stokes numbers less than 0.03, the sampling efficiencies are 100 f 20%, while for Stokes numbers larger than about 0.3 particle losses in the inlet become significant. On the basis of a large number of experimental data, the overall sampling efficiency of the inlet has been described accurately by a new nondimensional parameter consisting of Stokes number, gravitational deposition parameter, and Reynolds number.