It is therefore tempting to hypothesize that using several impellers makes a vessel's mixing behaviour approach the ideal represented by the simple dispersion model. Even though the improvements in the single-impeller tanks were modest in comparison to multi-impeller configurations, the mixing rates were nevertheless doubled. It would be interesting to study in the future, whether optimizing the feed point placement in single-impeller configurations would yield further gains. In previously published experiments , the use of two feed points resulted in 2.9 to 6.6-fold mixing rates in pneumatically agitated reactors. Interestingly, the corresponding two-feed-point rates were here as high as 5.6 to 15-fold in the simulated multi-impeller vessels (A, B, and C).