Convective diffusive mixing in concentration polarization: from Taylor dispersion to surface convection Academic Article uri icon

abstract

  • We analyse the steady-state convection–diffusion mixing of a solute by a creeping circulatory flow in a long sealed rectangular two-dimensional channel with impermeable sidewalls and fixed different solute concentrations at the two opposite edges. Solution circulation is due to a constant velocity slip along the sidewalls and a back flow along the channel axis. This simple model distils the essence of circulation in concentration polarization of an electrolyte solution under a DC electric current in a micro-channel sealed by an ion-selective element (a nano-channel or a cation exchange membrane). It is observed that in the slow circulation regime (small $ Pe $ numbers) the solute flux through the channel is governed by the Taylor–Aris dispersion mechanism, ie the flux is driven by the cross-sectional average axial concentration gradient, whereas upon increase in $ Pe …

publication date

  • August 1, 2013