TRANSPORT AND DEPOSITION OF SPHERICAL-PARTICLES AND FIBERS IN AN IMPROVED VIRTUAL IMPACTOR

Flow velocity in an improved virtual impactor was calculated for a Rey nolds number of 4000 using a finite-element method. The governing equa tions of motion for spherical particles and fibers were used along wit h flow field information to calculate transport and losses in the impa ctor. The calculated separation efficiency and loss fraction for spher ical particles agreed with experimental results reported in the litera ture. For fibers, separation efficiency curves were obtained in terms of fiber Stokes number and aspect ratio. The calculated collection eff iciency curve moved to higher Stokes numbers with increasing fiber asp ect ratio. All fiber sizes showed significant losses at the tip of the collecting probe of the impactor. As a result, the separation efficie ncy never reached 100%. The computational approach illustrated here ca n be used for predicting separation characteristics, which will lead t o improved and cost-effective design of the impactor. (C) 1997 America n Association for Aerosol Research.