Criteria for the Scaling Up of Mixing Vessels

Abstract

There are several concepts for the scaling up of mixing vessels. They are neither consistent nor conclusive. The authors propose an idea that the selection must be made depending upon the mixing objects. The classification of the types of scaling up is as follows : (1) Similarity for power requirement. Power requirement is correlated by Reynolds-, Froude- and Weber-numbers. The latter two are negligible in an ordinary correlation. (2) Similarity for mixing velocity of homogeneous liquid phase. The authors conclude that the similarity in blending speed is obtained by equal impeller speeds. (3) Similarity for heat and mass transfer on the fixed surface. Rushton et al. proposed the method of scaling-up by the following equation. (n₂/n₁)=(D₁/D₂)⁽²ˣ⁻¹⁾/ˣ This criterion should be limited in the case of the heat and mass transfer on a fixed surface. (4) Similarity for suspension of solid particles, dispersion of gas and liquid, and mass transfer on dispersed objects. The authors support the criterion of equal power per unit volume proposed by W.Büche.