PIV measurements of flow in an aerated tank stirred by a down- and an up-pumping axial flow impeller

Abstract

Liquid phase hydrodynamics in an aerated tank stirred by a down-and an up-pumping pitched blade turbine have been investigated using Particle Image Velocimetry. The effect of agitator configuration and the gas phase on the mean velocity fields and turbulent quantities in the vessel have been investigated. The global mean gas holdup has also been evaluated for the two pumping conditions. For the gas flow rate used, the presence of gas only slightly alters the liquid flow patterns produced by both the down-and up-pumping configurations and causes a general decrease in the mean liquid velocities. The turbulent kinetic energy in the impeller discharge region was not affected by the presence of gas, but in the bulk of the tank, aeration caused a decrease in this value. Global gas holdup was found to be ~36% greater for the up-pumping impeller and a large amount of gas was found to be entrained by the primary circulation loop.

Dynamic multidimensional modelling of submerged membrane bioreactor fouling

“…Techniques for hydrodynamic characterisation include the use of dye particles [4,6,7], flow velocimetry [4,8] and particle image velocimetry [9,10]. These techniques however, cannot easily be implemented in large scale systems that have large volumes, variable flows and opaque fluids.…”

Hollow self-inducing impellers: Flow visualization and CFD simulation

“…Here the diffusivities t,G and t,L are computed from the transport equations and the default value for GL is 0.75. Other forces such as lift and added mass force have not been included in the present simulation because of the low velocity gradients in the bulk region (Aubin et al, 2004;Montante et al, 2006). They have carried out detailed PIV measurements for the gas-liquid flows generated by axial flow impeller (PBTD45) and radial flow impeller (Rushton turbine) in baffled stirred vessel, respectively, and it has been observed that the liquid velocity profiles tend to be more or less flat in the bulk region.…”

Comparison of mixing in two industrial gas–liquid reactors using CFD simulations

“…These methods have also been recently used to characterize gas-liquid flows in mixing vessels (Aubin et al, 2004b;Morud and Hjertager, 1996;Ranade et al, 2001b). They provide detailed and very useful information to understand the complex and often turbulent flows occurring in these systems.…”