Multiple impellers blending

The Ekato intermig impeller has reverse pitch on the inner and outer blades and they are almost always used with multiple impellers. They are used at high D/T and promote a more uniform axial flow pattern than other turbine impellers. They are advertised to be very effective for solids suspension, blending, and heat transfer in the medium viscosity range. Lower Nrc limit not given by Ekato (9), perhaps 5. 

The lower impeller does the major part of the work on dispersing gas in the system and it is typical practice today to put a high proportion of the power into the lower impeller, somewhat similarto what is shown in Fig. 35. Multiple impellers do have zoning action in terms of blending, which is not a great factor in a fermentation which takes seven days, but there are instantaneous differences in the mass transfer, blending and concentration profiles in a tank with multiple impellers. 

M blend time to 95% reduction in variance for multiple impellers (s)... 

External jackets, 326-328 Helical coils, 312, 326, 327 Vertical coils, 326, 327 Mixing impellers, 290-297 Anchor, 290-329 Blending, 324, 326 Characteristic curves, 306 Chart to examine turbine applications, 296 Efficiency of propellers, 299 Flow of propellers. 298, 299 Flow patterns, 309-312 Gas-Liquid contacting, 324, 326 General list impellers, 291 Helical, 290, 329 Liquid-liquid dispersion, 326 Multiple, 297... 

The steady-state implicit impeller model, which uses time-averaged experimental data, can be used to model other steady-state and time-dependent processes, as described below. Because of its simplicity, it has no effect on other scalar transport in the domain. The models that do require special consideration are those involving multiple phases, with separate sets of momentum boundary conditions, as described below. Species blending is also discussed, because it is a calculation that is commonly performed in conjunction with the implicit impeller model. 

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