General Characteristics of Mixing Processes and Agitated Vessels

General Characteristics of Mixing Processes and Agitated Vessels 

Consider a vessel which contains two pure liquids, distinguishable by their compositions, which are ultimately miscible in each other. Assume that the fluids are segregated from each other when the observations begin, and that there are no mass-flow currents involving large numbers of molecules (i.e., the fluid is at rest. ) Now it is known from the kinetic theory that the individual molecules are in continuous motion. As time proceeds, this motion will result in an intermingling of the different molecules. This process is the classic one of molecular diffusion, 

Fortunately, molecular diffusion, assumed to be absent in the preceding discussion, proceeds simultaneously with the action of turbulence in the true situation. Thus, as the surface of contact between the com- 

The preceding discussion has been concerned with relatively small-scale phenomena. If we consider the entire body of liquid in a conventional mixing vessel, we see that intermingling of the unmixed components is also being carried out by the relatively gross transport of material in the large-scale flow patterns set up in the vessel by the 

Special-purpose impellers (BIO, L3, P3) are generally not difficult to classify on the basis above. The essential differences in performance of these special rotors are related to the nature of the turbulence they create (generally in the region near the impeller) rather than to the mean flow patterns. 

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II. General Characteristics of Mixing Processes and Agitated Vessels. .. 121... 

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