DEPOSITION OF DUST FROM TURBULENT GAS STREAMS

From an analysis of the theoretical and experimental results and their correlation by a number of workers it has been found that the deposition rate of fine particles on a smooth surface from turbulent gas flows (in the absence of gravitational or other external body forces, e.g. on the side wall of a duct) can be described by an equation of the form, No uτ c ̄∝ S*2 where No is the particle flux to the surface, uτ is the shear velocity, c ̄ is the mean concentration, and S* is the dimensionless stopping distance. This has been found by experiment to apply for particles approximately 0.5-50 μm dia. and for the range 0.3<S*<8. The corresponding ranges for the other variables are not known at present. The dimensionless stopping distance S* is a parameter of the particle-fluid system and for a particle in the Stokes regime with an assumed projection velocity of 0.9uτ, it can be shown that: S* = 0.05( uτd v2 σ ρ where d is the particle diameter, v is the fluid viscosity, and σρ is the relative density of particle to fluid. For very small particles, Brownian diffusion becomes significant, resulting in a minimum in. the curve of deposition rate versus particle size or flow rate. This has been observed. © 1969.