1992 Volume 18 Issue 4 Pages 487-494
In a dynamic filter with a rotating disk, the rotor should be such that the induced slurry flow completely sweeps a cake from a filter medium. To analyze the effects of shearing action on filtration flux, measurements of the tangential velocity distribution were carried out for a rotating grooved disk enclosed within a filter chamber without permeation using an non-Newtonian power law fluid (aqueous solution of sodium polyacrylate). The frictional resistance of the rotors was also studied experimentally.
The tangential velocity profile of the grooved rotor in the axial direction can be divided into three regions : boundary layers on the rotor and the fixed plate and fluid core between them. The flow consists of a laminar or turbulent flow with two separate boundary layers. With increasing number of grooves or their width, the tangential velocity increased fairly as compared with that for an ungrooved disk. The velocity profile could be evaluated in terms of the ratio K of the tangential velocities of the core and the rotating disk. The K-value was empirically determined from calculations based on newly defined operational factors, thus providing a method for estimating the velocity of the liquid in the filter. The torque coefficient Cm of grooved disks could also be correlated with the same factors for the K-value, using the torque coefficient Cm0 of an ungrooved disk.
