ISSN:
0032-3888
Keywords:
Chemistry
;
Chemical Engineering
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
,
Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
,
Physics
Notes:
The cross and down channel flows are analyzed in the center of an idealized leakproof intermeshing twin screw extruder chamber. The respective velocity components are assumed to vary only with channel depth. Because the screw flights block the cross channel flow, fluid circulates between two complementary channel depths in the cross channel direction just as predicted for single screw extruders. In addition, fluid circulates between an independent set of channel depths in the down channel direction due to the seal provided by the second screw lands. When the two fluid motions are considered simultaneously, a fluid particle is predicted to follow a complex path over a number of channel depths during its residence time in the extruder. This unique flow also causes particles which are initially near one another to eventually move to significantly distant locations. Furthermore, a wide range of velocities and shear rates is experienced by a fluid particle as it moves to the various channel depths. The strain predicted by two approaches is nearly uniform for the twin screw extruder product in striking contrast to the distribution of absolute strains found in single screw devices. The strain uniformity, wide shear history, and fluid separation predicted by this analysis of a limiting case may help explain the good mixing capabilities of these devices.
Additional Material:
5 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/pen.760200904
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