CONVECTIVE DIFFUSION TO A ROTATING-DISK

Convective diffusion to a rotating-disk electrode is investigated. A coordinate transformation is employed that removes the discontinuous nature of the surf ace boundary conditions at the electrode-insulator edge and difficulties associated with the treatment of boundary conditions specified for infinite values of the radial and axial coordinates. The transformation also accounts f or variations in the diffusion-layer thickness caused by changes in stir rates or fluid properties. For the transport-limited condition, the average current and the current distribution are functions of two dimensionless groups only: the Schmidt and Reynolds numbers. The current response is bounded by the Levich equation for large Schmidt and Reynolds numbers and by the well-known equation for the current response of a stationary disk in the limit of zero Schmidt or Reynolds numbers. Additional interfacial kinetic parameters are considered below the transport-limited condition.