A numerical study of inertial errors in anisokinetic sampling

A numerical study has been made of the anisokinetic sampling of aerosols from a flowing gas stream by a thin-walled tube. The sampling error due to anisokinetic sampling conditions has been calculated for various ratios of the free stream gas velocity, W, to the mean gas velocity, V, in the sampling tube. The performance of the sampling inlet is characterized by an aspiration coefficient, A, a penetration coefficient, P, and a loss coefficient, L. The values of A, P, and L have been calculated numerically and correlated with the Stokes number and the velocity ratio by means of simple equations. The numerical results for the aspiration coefficient have been found to be in good agreement with the classical study of Belyaev and Levin [J. Aerosol Sci. 3, 127 (1972); 5, 325 (1974)] in the velocity ratio, W/V, range of 0.2-5. Outside this range, some discrepancies were found and the classical Belyaev and Levin's results gave increasingly less accurate results.