Strain mode of general flow: Characterization and implications for flow pattern structures

Understanding the mixing capability of mixing devices based on their geometric shape is an important issue both for predicting mixing processes and for designing new mixers. The flow patterns in mixers are directly connected with the modes of the local strain rate, which is generally a combination o...

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Bibliographic Details
Published in:AIChE journal 2016-07, Vol.62 (7), p.2563-2569
Main Authors: Nakayama, Yasuya, Kajiwara, Toshihisa, Masaki, Tatsunori
Format: Article
Language:English
Subjects:
Chemical engineering
Chemical engineers
Disks
distributive mixing
Elongation
extrusion
food processing
Mixers
polymer processing
Screws
simulation
Spatial distribution
Strain rate
twin-screw extruder
Volumetric strain
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Summary:Understanding the mixing capability of mixing devices based on their geometric shape is an important issue both for predicting mixing processes and for designing new mixers. The flow patterns in mixers are directly connected with the modes of the local strain rate, which is generally a combination of elongational flow and planar shear flow. We develop a measure to characterize the modes of the strain rate for general flow occurring in mixers. The spatial distribution of the volumetric strain rate (or non‐planar strain rate) in connection with the flow pattern plays an essential role in understanding distributive mixing. With our measure, flows with different types of screw elements in a twin‐screw extruder are numerically analyzed. The difference in flow pattern structure between conveying screws and kneading disks is successfully characterized by the distribution of the volumetric strain rate. The results suggest that the distribution of the strain rate mode offers an essential and convenient way for characterization of the relation between flow pattern structure and the mixer geometry. © 2016 American Institute of Chemical Engineers AIChE J, 62: 2563–2569, 2016
ISSN:0001-1541
1547-5905
DOI:10.1002/aic.15228