The flow patterns generated by the rotation of stirrer bars in the two immiscible liquids in a stirred vessel extractor have been approximated by a simpliΓΓ¬ed model. Each phase was divided into two regions: the core region, whΓch is the cylindrical volume swept out by the sthrer bars, and the outer annular region, which comprises the remainder of the phase. The flow in the core region has been assumed to be equivalent to that generated by an intΓ―nite body of fluid in solid body rotation over a surface rotating at a slower rate. The axial velocity in the outer ammlus is then obtained by a simple material balance. Knowledge of the velocity profile in this latter region permitted a direct solution of the diffusion equation, which in turn resultcd in a purely thcoretical mass-transfer correlation for this extraction device.
Comparison of the experimental data and the thcorctical predictions showcd the latter to he approximately 35-50 per cent too low; this agrcement was considercd sutlìciently close to warrant tentative acceptance of the flow model upon which the theorctical prcdictions were ba&. Two important conclusions which follow from the model are: (1) a turbulent transport mcchanism nood not hc postulatcd for extraction in a sthmd vcssel of the typc considercd hem, since a purcly laminar flow model comes quite close to reproducing the ohservcd extraction ratcs; and (2) rippling of the interface does not rcsult in pronounccd increases in the mass-transfer cocfficient, sincc the flow model was bascd upon a planar interface, and the expcrimentai data rcprcsent various degreos of intcrfacial rippling.