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Mass Transfer of Diffusive Species with Nonconstant In-Flight Formation and Removal in Laminar Tube Flow. Application to Unattached Short-Lived Radon Daughters

This article deals with convective-diffusive aerosol transport with in-flight formation and removal and is applied to the unattached fraction of short-lived radon decay products. Two novel contributions to previous studies are 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 the other hand, we include the 218Po 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 development of simple correlations for the 214Pb and 214Bi penetration fractions. Those correlations can be used to determine the diffusion coefficient of 214Pb and 214Bi using the 2-filter method. In our experiments, a diffusion coefficient equal to 5 X 10-6 m2 s-1 is found for the 214Pb. Concerning the 218Po neutralization, better agreement is observed between our numerical and experimental results when 218Po neutralization is taken into account. These results confirm the neutralization rates found by Howard and Strange (1994).