The Voidage Function on Particle-to-fluid Mass Transfer in a Packed Bed

Abstract

In this paper, the effects of voidage on the rate of mass transfer from the surface of one particle to the fluid in a dilute packed bed are treated.In order to determine the mass transfer rate for one active sphere in a bed and compare with that obtained for a single sphere in our previous report, the bed consisted of the central active (10 mmφ camphor) sphere and a sufficient number of regular packed (10 mmφ urea resin) spheres that were strung on 1.1 mmφ steel wires. The voidages of the three orthorhombic assemblages investigated are 0.924, 0.821 and 0.718.In such a high voidage, there exists a laminar boundary-layer flow over a wide range of the Reynolds number, and then the Sherwood number can be expressed as follows: Sh=A+B Re1/2which is comparable to the equation for a single sphere. It is reasonable to assume that B, which is determined mainly by a similar transformation variable, η, or by the geometric factor for Uθ (x), contains the voidage parameter (a/b).Using these values of B for each assemblages and that for a single sphere, the voidage function, f (a/b) , on the particle-to-fluid mass transfer in a packed bed is obtai ned.