Mass transfer coefficients associated with the mixing of a confined gas volume by the random motion of loose spheres

This investigation quantifies the change in mass transfer within a confined gas volume subjected to mixing by loose spheres. A cylindrical vessel containing between 1 and 50 Teflon spheres in a tracer gas is vigorously shaken. Extractive sampling provides time histories of tracer gas concentrations extracted from the vessel. Fitting the results from a simple 1-D mass transfer model to the experimental data yields an effective mass transfer coefficient k′ for each experimental condition. Compared to diffusive mass transfer where k′ = D_ab = 7.58 × 10^?6 m²/s, k′ exhibits a cubic dependency on the number of spheres with a maximum at 17 spheres where k′ = 3.5 × 10^?3 m²/s.