Intermittent convection: confirmation of a model for mass transfer into stratified fluid layers

Abstract

A series of nonsteady mass transfer experiments has been performed with sulfur dioxide being absorbed into deep water layers. For this system the layer is subject to density-driven instabilities, and the rate of absorption is controlled by the resulting convective motion. The time course of the mass transfer rate was monitored from the initiation of absorption up to times approaching total saturation of the layer, a period several times greater than that corresponding to onset of first motion. These rate data were used to reveal features of the convective motion. The mass transfer results are shown to be consistent with an intermittent convection model based on the concept of a periodically erupting boundary layer, a model first proposed by Howard [14]. Interestingly, the predicted mass transfer behavior has features of conventional surface renewal theory, but with the additional facet that the renewal rate is directly relatable to the instability of the boundary layer. The combined effects of buoyancy and mechanically induced convection were explored in one series of experiments. In addition, we have resolved some inconsistencies which have appeared in recent publications concerning the stability criterion for the SO 2/water system.