A novel method to capture mass transfer phenomena at free fluid-fluid interfaces

A rigorous Computational Fluid Dynamics (CFD) based approach incorporating interfacial mass transfer at moving interfaces has been developed. The peculiarity of this approach is that it is able to govern multicomponent systems as well as interfacial boundary conditions in an arbitrary form. This is important in order to properly handle the typical concentration jump at the phase interface and to avoid an assumption of a constant distribution coefficient which is seldom met in real separation units. As a test system, the movement of a rising toluene droplet in quiescence aqueous phase is studied, whereas acetone is used as the transferring component. The level set method is applied for the description of the droplet movement. To give a first validation to the developed CFD model, the toluene droplet is first assumed to be stagnant and the mass transfer from/to the continuous aqueous phase is considered. A good agreement with analytical results from the literature is found in terms of the asymptotic value of mass transfer rate. Further, simulations for rising droplet are performed to incorporate the coupling between the momentum and mass transfer. The method provides concentration fields that are in qualitative agreement with the available data from the literature. Another test accomplished with an increased distribution coefficient also yields reasonable results. (C) 2010 Elsevier BM. All rights reserved.