5. Mass Transfer
Mass and heat transport to the walls of a Taylor device have been thoroughly studied. For the sake of concision, however, these phenomena will not be addressed here, because VFRs with immobilized enzymes generally work with suspended particles. Hence, the most important mass transfer parameters of the reactor are related to bed dispersion and to the transport through the particles' external film. Of course, intraparticle, pore-diffusion resistances may be significant, but this point is independent of the reactor configuration and therefore is out of our present scope.
Several authors have proposed macro-flow models for VFRs. Essentially, models with one, two, or three parameters are presented in the literature (16). Depending on the specific application, models that are more complex may be necessary. Nevertheless, for preliminary calculations the simplest, one-parameter approach might suffice. This is the classical axial dispersion model, and Moore and Cooney (25) presented a correlation for this parameter, spanning laminar and turbulent vortices:
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