Abstract
Thin-cake filtration with cylindrical dynamic filter can be achieved by applying an intensive shear to the liquid and a Taylor vortex flow in the annular space between two coaxially arranged filter cylinders. To determine the operational factors affecting the power required for a rotating inner cylinder, the frictional resistance of grooved rotors in the filter chamber without permeation or throughflow was studied. The effect of the groove and chamber dimensions on the transition to Taylor vortex flow was analysed, using a flow-visualization technique.
The groove effect on the frictional resistance was represented by means of a newly defined factor, taking into account the number of grooves and their width. The rotating torque of the inner cylinder was evaluated in terms of the relationships among three main factors : the ratio of groove to rotor surface area, the ratio of annular gap width to inner cylinder radius, and the rotor Reynolds number. Empirical equations of the frictional coefficient as a function of the operational variables were proposed for the flow region of Taylor vortices. It is shown that the rotating power of the grooved rotor has the same value as that of the smoothed rotor provided the surface area ratio is below a critical value. The critical Reynolds number is also determined for estimating the onset of instability in laminar flow with Taylor vortex formation.
