Electrochemical mass transfer studies in annuli

Abstract

Rates of mass transfer in conditions of transport control and in the mass transfer entry region have been determined by measuring limiting currents for the deposition of copper from acidified solutions of copper sulphate on to copper cathodes of different lengths. The cathodes formed part of the inner wall of an annular flow cell and conditions were such that in both streamline and turbulent flow the hydrodynamic conditions were fully developed at the mass-transfer section. The variation of the mass transfer coefficient with electrode length has been clearly demonstrated, and results for streamline flow have been compared with a form of the Lévêque equation suitably modified to account for the annular geometry. The data have been successfully correlated by the equation▪ for an annulus radius ratio of 0-5. For annuli of radius ratios 0·25 and 0·125 the constant in the correlating equation was found to increase in the manner expected from velocity-profile considerations.In turbulent flow with an annulus diameter ratio of 0-5, experimental data have been correlated by tile equation▪