Ionic mass transfer in turbulent flow by electrodialysis with ion exchange membranes

Abstract

The rate of ionic mass transfer at the limiting current density was measured in two-dimensional flows both laminar and turbulent, through a channel between a pair of ion-exchange membranes. The results obtained were independent of the properties of the membranes, because the mass transfer rate at the limiting current density was mainly controlled by the transport process through the boundary layers in the desalting cell. For laminar flow, the experimental results showed good agreement with those of numerical analysis, in which the rate was assumed to be controlled by the boundary layers produced near the membrane surfaces. For turbulent flow, the analytical results were also brought into good agreement with the experimental results, by introducing a new concept of the “eddy migration coefficient”, and by putting 0.0086 (Em/v)1.0. Em is the eddy diffusivity for momentum and V is the kinematic viscosity. According to these results, the local electric conductivity in an intensely agitatd fluid may be greater than that in a stationary solution by 5 to 10%. © 1970, The Society of Chemical Engineers, Japan. All rights reserved.