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High Shear Mixers
Inline rotor-stator mixers are broadly employed in chemical processes
to produce emulsions, dispersions, and multiphase gel networks,
and to control particle size. Despite their widespread use, there
is almost no fundamental basis for assessment of their performance.
Process development, scale-up and operation are often by trial and
error, leading to increased processing costs, start-up problems
and lost time-to-market.
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These two-dimensional sliding mesh simulations of an in-line rotor-stator
mixer, while approximate, provide considerable insight and a basis
for experimental design. Fixed frame LDA measurements have been
performed that partially validate the simulations, while further
elucidating the complexity of the flow field. This combined CFD-LDA
study provides considerable insight into rotor-stator mixer performance,
even in the absence of empirical data. Future work is planned to
further the understanding of the single phase and multiphase fluid
dynamics. This work was done as part of the High Shear Mixing Research
Program at the University of Maryland.
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Inline-slurry Mixers
In this case, the project engineers modified and improved an initial
design concept, built the mixer and directly installed it at the
production mill. This allowed the engineers to skip the bench scale
and pilot scale testing. The pulp was modeled as a pseudoplastic
fluid mixed with Newtonian fluid. The main challenge for the engineers
during the CFD analysis was reaching mesh independence for mixing
efficiency. Once the mixer was installed at the mill, the horsepower
and pressure drop predictions were within 10% of measured performance,
a very good result.
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