Page 279 - Academic Press Encyclopedia of Physical Science and Technology 3rd Chemical Engineering

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Encyclopedia of Physical Science and Technology EN006C-252 June 27, 2001 14:15

Fluid Mixing

J. Y. Oldshue
Mixing Equipment Company, Inc.

I. General Principles
II. Scaleup Relationships
III. Liquid–Solid Contacting
IV. Gas–Liquid Contacting
V. Liquid–Liquid Contacting
VI. Blending
VII. Fluid Motion
VIII. Heat Transfer
IX. Continuous Flow
X. Pilot Plant Procedures
XI. Computational Fluid Dynamics

GLOSSARY duce a uniform velocity across the entire face width of
the axial flow impeller.
Axial flow impellers Impellers that pump the fluid pri- Fluid shear rate Velocity gradient at any point in the
marily in an axial direction when installed in a baffled mixing tank.
mixing tank. Fluid shear stress Product of shear rate and viscosity,
Chemical or mass transfer criteria Criteria for fluid which is responsible for many mixing phenomena in
mixing evaluation that involves measuring the rate of the tank.
chemical reactions or rates of mass transfer across liq- Macroscale mixing, macroscale shear rates Particles
uid, gas, or solid interfaces. on the order of 500–1000 µm and larger, or fluid ele-
Computational fluid mixing Computer programs that ments of this size, respond primarily to average veloc-
use velocity data to calculate various types of flow pat- ities at any point in the tank and are characterized as
terns and various types of fluid mechanics variables macroscale shear rate sensitive or related to macroscale
used in analyzing a mixing vessel. mixing. Visual inspection of a tank normally yields in-
Fluidfoil impellers Axial flow impellers in which the formation on the macroscale mixing performance.
blade shape and profile is patterned after airfoil con- Microscale shear rates, microscale mixing Any parti-
cepts. The blade normally has camber and has a twist cles or fluid elements on the order of 100 µm or less re-
in toward the shaft with a rounded leading edge to pro- spond primarily to the fluctuating velocity components

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