Dean vortices-induced enhancement of mass transfer through an interface separating two immiscible liquids

Two-fluid Dean vortex flow in a coiled pipe with vanishing torsion, and its effect on the 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 pipe. The Navier–Stokes equations in both fluid layers are solved numerically by the finite volume method. The results reveal a detailed structure of the transverse flow (the Dean vortices) in coiled pipes with the dimensionless curvature 0.1. Both cocurrent and countercurrent axial flows in the fluid layers are considered. Using the flow fields predicted, the mass transfer equation is solved. It is shown that the mass transfer of a passive scalar (say, a protein with the Schmidt number of the order of 103) through the interface can be significantly enhanced by the Dean vortices, so that the mass transfer rate can be increased by three to four times. This makes the Dean vortex flow an effective tool for mass transfer enhancement ...