Hydrodynamic Characterization of Three Axial Impellers under Gassed and Ungassed Conditions

Abstract

We investigate the hydrodynamic performance of a ba ed stirred tank for an air-water system in the turbulent regime. Comparisons among three di erent axial impellers were conducted: Maxblend impeller, two coaxial Pitched Blade Turbine (down-pumping mode) and two coaxial Intermig impellers. Measurements of the mean velocity eld and the power consumption for gassed and ungassed conditions were obtained. The gas phase was introduced in a controlled manner using a capillary bank mounted at the bottom of the tank. The measured distributions of turbulent intensities for each impeller system for both gassed and ungassed con gurations showed signi cantly di erent distributions. The ow patterns were also drastically modi ed for gassed conditions for the conventional agitators. The Maxblend impeller was observed to maintain a certain degree of homogeneity in the turbulent distribution for both gassed and ungassed conditions.

Friction Factor Distribution at the Side Wall of a Turbulent Agitated Vessel with Baffles Using a MAXBLEND Impeller

“…In addition, a large vortex can be seen in the range of z/H > 0.4 in the case without baffle clearance, which is consistent with previous experiments. 29,30 When the clearance was added between the sidewall and baffles, the flow in z/H > 0.4 became more complex. The single circulation observed in the vessel without baffle clearance was divided into two circulations.…”

“…The MAXBLEND impeller is a plate-shaped impeller consisting of a bottom paddle and an upper grid. The hydrodynamic characteristics of the MAXBLEND impeller, which typically generates a vertical circulating flow pattern, have been investigated in laminar 27,28 and turbulent 29,30 regions and in both Newtonian 31 and non-Newtonian fluids. 32−34 The MAXBLEND impeller shows superior performance in many kinds of processes.…”

“…The MAXBLEND impeller is a plate-shaped impeller consisting of a bottom paddle and an upper grid. The hydrodynamic characteristics of the MAXBLEND impeller, which typically generates a vertical circulating flow pattern, have been investigated in laminar , and turbulent , regions and in both Newtonian and non-Newtonian fluids. − The MAXBLEND impeller shows superior performance in many kinds of processes. Takahashi et al experimentally measured the bubble size in an aerated mixing tank and reported that the MAXBLEND impeller can disperse almost uniform size bubbles throughout the vessel compared to a dual Rushton turbine.…”