Suction effects on the hydrodynamics in the vicinity of an ultrafiltration plane ceramic membrane

The wall shear stress is determined at the surface of a plane ceramic ultrafiltration membrane in a tangential ultrafiltration module. At first, the shear stress is determined at the surface of a plate of Plexiglas mimicking a membrane and at the plane membrane surface without fouling particles with the aim to investigate the influence of permeation. Then, ultrafiltration of a suspension of spherical rigid particles inducing a deposit at the membrane surface is done. In order to study the influence of the foulant, two concentrations of particles were used for the experiments. The values of the mean wall shear stress and its fluctuations (turbulent intensity rate) were measured by using an electrochemical method. Twenty microelectrodes, on which an electrochemical reaction occurs, are mounted flush to the plate of Plexiglas and to the surface of the membrane to determine the maps of shear stress and turbulent intensity rate for two inlet/outlet distributors’ configurations. This work emphasized the fact that, due to permeation across the membrane, the mean velocity gradient value is enhanced and, on the contrary, its local fluctuations are clearly damped, even in the turbulent flow regime. Thus, the effect of the shape of the inlet/outlet fluid distributors is also minimized compared with the results obtained without permeation at the surface of the Plexiglas plate.