mass transfer from fluids to membrane
Hi,
I have some difficulty in modeling mass transfer in a membrane separation process. My question is: how to couple mass diffusion in a solid-like (not porous) membrane with mass transfer near the membrane surface? 1. Case description. Binary Fluid (with species B dissolved in water) flowing through a flat slit (2mm high, 20mm wide, 190 mm long). The bottom of this rectangular geometry is a nonporous membrane. Species B will be PREFERENTIALLY permeate through membrane to reach the other side of membrane where a high vacuum is applied. I use Gambit and Fluent 6. The difficulties I encounted included: 1) Fluent can just take membrane as SOLID, in this way I have no way to input diffusivity of B within membrane. Membrane in this case is still( not moving), yet it is not impermeable solid like steel. 2) How much B should go into membrane should be determined by concentration of B at membrane surface in contace with fluid. As Fluent seems to provide no model for mass diffusion in solid, I compromised to used surface reaction deposition model for this purpose. But in this way, the reaction rate is pretty arbitrary, though I can finally deterine the correct value by error-and-trial approach to let flux from fluid into membrane be the same as the flux through membrane to vacuum. Thanks for your help, Peter |
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