GRAVITATIONAL TRANSPORT OF PARTICLES IN PURE GASES AND GAS-MIXTURES

Sedimentation velocities of 0.96- and 1.52-mum monodisperse polystyrene latex particles in pure gases and gas mixtures at 23-degrees and 37-degrees-C have been measured using a sedimentation cell. The gases used for the measurement were N2, O2, Ar, He, CO2, SF6, air, 80%He-20%O2, 70%He-20%O2-10%N2, 80%SF6-20%O2, 70%SF6-20%O2-10%N2 and 80%Ar-20%O2. Calculations of the terminal sedimentation velocity were also done using the parameters appropriate for the particles and the gaseous media. There was good agreement between the observed and the predicted sedimentation velocities. The measured sedimentation velocities ranged from 28.5 mum s-1 in Ar to 40.2 mum s-1 in He for 0.96 mum and from 65.6 mum s-1 in 80%Ar-20%O2 to 96.8 mum s-1 in CO2 for 1.52-mum aerosols at 23-degrees-C. At 37-degrees-C the values were generally lower (within 5%) than at 23-degrees-C. The sedimentation velocities in 80%He-20%O2, 70%He-20%O2-10%N2, 80%SF6-20%O2, 70%SF6-20%O2-10%N2 gases were within 11% and in 80%Ar-20%O2 within 20.4% of those in air.