Mass transfer of diffusive species with nonconstant in-flight formation and removal in laminar tube flow. Application to unattached short-lived radondaughters

This article deals with convective-diffusive aerosol transport with in-flig ht formation and removal and is applied to the unattached fraction of short -lived radon decay products. Two novel contributions to previous studies ar e given in this numerical and experimental work: on the one hand, we solve the mass-transport equations for all the short-lived radon daughters; on th e other hand, we include the Po-218 neutralization into the mass-transport equation of the first radon decay product. Concerning the mass-transfer of all short-lived radon daughters, numerical calculations lead to the develop ment of simple correlations Pb-214 and Bi-214 penetration fractions. Those correlations can be used to for the Ph and Pb-214 and Bi-214 using the 2-fi lter method, In determine the diffusion coefficient of Pb and our experimen ts, a diffusion coefficient equal to 5 X 10 (- 6) m(2) s (- 1) is found for the Pb-214. Concerning the Po-218 neutralization, better agreement is obse rved between our numerical and experimental results when Po-218 neutralizat ion is taken into account. These results confirm the neutralization rates f ound by Howard and Strange (1994).