The vortex wave membrane bioreactor: hydrodynamics and mass transfer

Abstract

An experimental study of a membrane bioreactor has investigated the dynamics of the vortex wave as an effective aeration technique for application in high density mammalian cell culture. Gas transfer membranes have been employed in order to eliminate the potentially lethal gas\3-liquid interface found in stirred tank and bubble columns. The diffusion-limited features of oxygen transfer through a membrane have been overcome by harnessing the excellent mixing characteristics of oscillatory flow and vortex formation.

The crucial hydrodynamic features of the vortex wave, in a relatively wide channel, have been classified in terms of deflector spacing, Reynolds number and Strouhal number. The dynamic gassing-in of oxygen from a gas phase, across the membrane, to a liquid phase has allowed us to quantify the mass transfer characteristics in terms of the Sherwood number. Significant mass transfer enhancement has been achieved under laminar flow conditions, without a major increase in power dissipation. The Sherwood number has been found to be dependent on both the Reynolds number and the Strouhal number. The Reynolds analogy has been employed to calculate shear rates. The low shear rates (about 300 s{su\t-1}) and maximum theoretical hybridoma cell densities (about 1.0 \sx 10{su9} cells ml{su\t-1}) indicate that the vortex wave design may be an effective alternative to traditional bioreactors.