Hydrodynamics in an Aerated Tank Stirred by a Down-and an Up-Pumping Axial Impeller

摘要

Liquid phase hydrodynamics in an aerated tank stirred by a down- and an up-pumping pitched blade turbine have beeninvestigated using Particle Image Velocimetry. The effect of agitator configuration and the gas phase on the meanvelocity fields in the vessel have been investigated. The global mean gas holdup has also been evaluated for the twopumping condition. In the down-pumping case, one circulation loop was formed in the lower half of the tank, whereas inthe up-pumping configuration, a secondary loop in the upper part of the vessel was also produced. In both cases, themaximum axial and radial velocities were less than in the single phase flow case. Global gas holdup was found to be～20% greater for the up-pumping impeller and a large amount of gas was found to be entrained by the primarycirculation loop.