Mass or heat transfer accross a plane membrane placed in the way of a flowing stream: Effect of stepwise and/or exponential concentration or temperature changes

Abstract

The description of the function of modern membrane-covered electrodes of the polarographic type at dynamic methods leads to the solution of diffusion equation using special boundary and initial conditions. This paper summarizes the results of numerical solution of the diffusion equation at these conditions over a wide range of the parameters characterizing the properties of the electrodes and the surrounding medium under study. Expressions for dimensionless mass or heat flow through a slab placed in the way of a flowing stream are summarized for the case where at the first slab side the concentration (or temperature) is maintained zero while at the second side bypassed by the stream there is an exponential or stepwise concentration (or temperature) change. The effect of non-ideal changes is also studied. Corresponding analytical solutions of the diffusion equation were evaluated and the results are presented graphically, allowing to express the mass or heat transfer intensity as a quantitative function of the hydrodynamic resistance to mass or heat transfer as well as of the concentration (or temperature) change non-ideality.