Industrial Mixing Basics: Mixing Impeller Flow Patterns

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ProQuip In the Mix Vlog - Mixing Impeller Flow Patterns Feature Image

A primary classification of industrial mixer impellers is their liquid flow pattern in a mixed vessel.  This characteristic is used to provide the type of mixing that is desired for a particular application.

Axial Flow Pattern

Axial flow impellers are designed to provide primarily an up and down flow pattern.  This flow pattern develops using a center mounted axial flow impeller in a “fully baffled” tank. A center mounted, axial flow impeller in a non-baffled tank will result in rotation of the fluid with little top to bottom motion. This was demonstrated in a previous blog discussing baffled vs non-baffled tank mixing.

Applications of axial flow impellers include flow controlled liquid blending and solid suspension of particles.

CFD (Computational Fluid Dynamics) can be used to show liquid flow patterns created by an axial flow impeller.  The velocity contour plot below shows high velocity below the impeller. The direction and magnitude of flow is shown by a Velocity Vector plot.

Illustration of Axial Flow Hydrofoil Impeller Flow Pattern High Velocity Below Impeller

Illustration of the direction and magnitude of flow is shown by a Velocity Vector plot

The above CFD plots were scaled to match the following lab tank video demonstrating an axial flow pattern.  The video shows a ProQuip HiFlowTM Impeller (axial flow hydrofoil impeller), center mounted in a lab scale baffled tank. The liquid is water.  Colored beads are added to aid visualization of the top to bottom flow pattern.

 

ProQuip HiFlow TM Impeller

ProQuip Impeller design ProQuip HiFlow

Other axial flow impellers include pitched blade turbines. These impellers also create top to bottom flow patterns but with higher fluid shear rate and power draw compared to High-Efficiency hydrofoils.

Axial Turbine Impeller (45o pitched blade)

ProQuip Axial Turbine Impellers

Radial Flow Pattern

A radial flow impeller provides primarily a side to side flow pattern in a baffled tank.  This impeller design provides higher shear to flow compared to axial flow turbines.  Typical applications include placement of the impeller close to the bottom of a tank for sweeping vessel floor.   Other configurations include high shear applications for solid or gas dispersions.

The CFD plots below are for a radial turbine impeller.  The velocity contour plot shows high velocity between the impeller and the tank wall. The direction and magnitude of flow is shown by a Velocity Vector plot.

Illustration of Radial Turbine Impeller Flow Pattern High Velocity Below Impeller
Illustration of velocity vector plot showing the direction and magnitude of flow for a radial turbine impeller

The above CFD plots were scaled to match the following lab tank video demonstration for a radial turbine.  This video demonstrates the flow pattern for a 90o, 4-blade radial flow impeller.  The impeller is center mounted in a lab scale baffled tank.  The liquid is water.  Colored beads are added to aid visualization of the flow pattern.

Radial Turbine Impeller (90o blade)

 

For More Information on Mixing Impeller Flow Pattern

For more information about mixing impeller flow patterns, email applications@proquipinc.com, call us at 330-468-1850 or view our blog on mixing impeller types.