Experimental observation of aerosol deposition in turbulent flow

Abstract

The deposition rate of aerosol particles in turbulent flow has been measured in vertical pipes for nominal Reynolds numbers of 10,000 and 50,000 and for particle dia. of 1·4–21 μm using monodisperse aerosols generated by the vibrating orifice monodisperse aerosol generator. The experiments covered a τ + range of 0·21–774, where τ + is the dimensionless particle relaxation time. For small τ + values, the deposition velocity was found to increase rapidly with increasing particle size, reaching a peak at τ + = 30. Beyond τ + = 30, the dimensionless deposition velocity, V +, showed only a moderate dependence on τ +, decreasing slightly at higher τ + values. Below τ + = 10. V + was found to increase as the second power of particle relaxation time and as the fourth power of particle size. The experimental results are in good agreement with several of the existing theories in the region below τ + = 30. However, the theories are inadequate to explain the results beyond τ + = 30.