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Effect of liquid level and agitator pumping direction on turbulent blend times
Jan 25, 2016

With the impeller placed low in the tank (C/T=1/3), turbulent blend times produced by radial-flow and down-pumping axial-flow impellers generally increase slowly with increasing liquid level in shorter batches (Z/T<1), but increase dramatically in taller batches (Z/T>1). The turbulent blend times produced by up-pumping axial-flow impellers increase slowly with increasing liquid level across the entire spectrum of liquid levels that were studied (up to Z/T=1.75). This can lead to down-pumping blend times that are twice as long as those with up-pumping operation. These differences can be explained by differences in the velocity field in the agitated vessel. Further, the down-pumping mode can produce blend times in tall tanks that are comparable to those of the up-pumping mode if the down-pumping impeller is placed high in the batch such that its discharge flow is directed into the bulk of the liquid.

 

See more at: http://onlinelibrary.wiley.com/doi/10.1002/cjce.21868/abstract