The answer to non-geometric scale-up all depends on the process and how dissimilar the geometry is.  While geometric similarity often helps scale-up, it is not always necessary for basic blending, heat transfer, or other bulk uniformity processes.  Often, being sure that the impeller torque per volume is the same for the two scales can be sufficient.  It the process is a function of a multi-step chemical reaction, the power per volume may need to be a constant.  Many dispersion problems can be scaled on the basis of equal impeller tip speed.  Solids suspension is more geometry dependent so scale-up with non-geometric similarity can be difficult.  All of these rules-of-thumb are very general, with many specific exceptions.  Even geometric similarity does not always successful scale-up.

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