Convection-induced enhancement of mass transfer through an interface separating two immiscible liquids in a two-layer horizontal annulus

Two-fluid natural-convection flow in the horizontal cylindrical annulus and its effect on mass transfer through the liquid-liquid interface of two immiscible fluids are studied numerically. The liquids are stratified by gravity, with the denser one occupying the lower part of the annulus. The convective motion is driven by heating of the inner or outer cylindrical boundary. It is shown that the mass transfer of a passive scalar (say, a protein) through the interface can be significantly enhanced by the convective flow. Varying the radii ratio from 0.1 to 0.5, it is found that the mass transfer is more intensive in annuli with smaller radii ratio. No significant difference in the mass transfer rates was found between the heating of either inner or outer cylinder. A possibility of further mass transfer enhancement using more complicated temperature distribution on the boundaries is demonstrated. The problem is related to the search for novel bioseparator devices.