Dipl.-Ing. Kathrin Dieter-Kissling
Multicomponent mass transfer to and on liquid and solidsurfaces
Multicomponent mass transfer both in bulk phases and on fluid or solid interfaces plays an important role in chemical engineering. Well known application areas can be found in the chemical reaction technology, i.e., pourous media as support of catalysts or in the extraction technology. To properly describe the transport processes in these systems the multicomponent species transport mechanisms need to be described.
During the current project a simulation tool on the basis of the open source CFD library OpenFOAM will be developed, which will be capable of solving the strongly coupled transport processes regarding the multicomponent diffusion processes. Moreover fluid and solid interfaces will be taken into account. A segregated solution procedure does not represent the correct physical behaviour of such systems. Therefore, a coupled solution procedure needs to be applied, using block-structured solution techniques. The diffusive mass flux is modeled by adopting the Maxwell-Stefan equations, which in contrary to Fick’s law can comprehensively describe the effects of multicomponent diffusion like cross diffusion effects, osmotic diffusion or diffusion barriers. In order to insert these fluxes in the governing species transport equations, the Maxwell-Stefan equations need to be effectively inverted. The model is validated according to the known test cases from literature, e.g., the diffusion tubes according to Stefan or Loschmidt or the two bulb diffusion experiment according to Duncan and Toor. To describe the coupled transport processes on the interface, the Maxwell-Stefan equations need to be adapted for surface specific transport properties on curved surfaces. The numerical solution method is based on the Finite-Area Method by Tukovic and Jasak. With the multicomponent background, a coupled solution procedure must be applied analogue to the bulk flow. To couple the processes the phase’s interior with the interfacial processes, thermodynamical consistent transmission and coupling conditions need to derived from the partial momentum and mass balances of a single species. To realize this coupling in the numerical simulation a multiregion method is applied.
The multicomponent transport in the bulk phase is investigated in a Loschmidt tube. We apply a coupled solution procedure which uses an iterative matrix inversion algorithm according to Giovangigli to compute the diffusive fluxes from the Maxwell-Stefan equations. The preliminary results are shown in the picture below.