Figs. 6 and 7 show the effect of cross-flow velocity on permeation
flux of alumina and titania slurries, respectively, indicating
that the flux increases with increasing cross-flow velocity, principally
due to the fact that resistance of filtered cakes was reduced
since the thickness of cakes was reduced by increasing the crossflow
velocity. It is evident that the shear stress, which determines
the thickness of the cakes, was produced by the tangential multiphase
flow. Evaluation of shear stress is the main approach for
understanding filtration performance (Hwang & Wu, 2008). In general,
the higher the cross-flow velocity, the higher the flux, thus
leading to higher washing efficiency. However, high cross-flow
velocity will lead to higher energy consumption. More importantly,
high cross-flow velocity calls for certain strict requirements on production
equipment, especially for the selection and maintenance
of pumps. For cost-effectiveness, in a real industrial process, the
cross-flow velocity is usually chosen to be 5 m/s.