Isokinetic sampling of aerosols from tangential flow streams

A comprehensive analysis of inertial effects in aerosol sampling was combined with a thorough study of swirling flow patterns in a stack following the exit of a cyclone in order to determine the errors involved in sampling particulate matter from a tangential flow stream. Two simultaneous samples, one isokinetic and the other anisokinetic, were taken from a 10 cm wind tunnel and compared to determine sampling bias as a function of Stokes number. Monodispersed uranine particles, generated with a spinning disc aerosol generator, and mechanically dispersed ragweed pollen were used as experimental aerosols. The duct velocity was varied from 550 to 3600 cm/sec and two nozzle diameters of 0.465 and 0.683 cm were used to obtain values of Stokes numbers from 0.007 to 2.97. Experiments were performed at four angles, 0, 30, 60 and 90 degrees, to determine the errors encountered.