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Effects of geometry and flow rate on secondary flow and the mixing process in static mixers - A numerical study

Regner, Mårten LU ; Östergren, Karin LU and Trägårdh, Christian LU (2006) In Chemical Engineering Science 61(18). p.6133-6141
Abstract
A method based on computational fluid dynamics (CFD) for the characterization of static mixers using the Z factor, helicity and the rate of striation thinning is presented. These measures were found to be well-suited for the characterization of static mixers as they reflect the pressure drop, the formation of secondary flow, i.e. vortices, and their effect on the mixing process. Two commercial static mixers, the Kenics KM and Lightnin Series 45, have been characterized. In the mixers investigated, secondary flow is formed in the flow at the element intersections and due to the curvature of the mixer elements. The intensity of the vortices is higher in the Lightnin than the Kenics mixer due to edges in the middle of the Lightnin mixer... (More)
A method based on computational fluid dynamics (CFD) for the characterization of static mixers using the Z factor, helicity and the rate of striation thinning is presented. These measures were found to be well-suited for the characterization of static mixers as they reflect the pressure drop, the formation of secondary flow, i.e. vortices, and their effect on the mixing process. Two commercial static mixers, the Kenics KM and Lightnin Series 45, have been characterized. In the mixers investigated, secondary flow is formed in the flow at the element intersections and due to the curvature of the mixer elements. The intensity of the vortices is higher in the Lightnin than the Kenics mixer due to edges in the middle of the Lightnin mixer elements. The formation of vortices affects the Z factor by an increase in the power requirement, and the rate of striation thinning by an increase in the stretching of the striations. The formation of vortices was observed at a Reynolds number of 10 in both mixers with aspect ratios of 1.5. However, the intensity of the vortices was greater in the Lightnin than the Kenics mixer, which was observed in not only the magnitude of the helicity, but also the Z factor, rate of striation thinning and the distribution of striation thickness. The distribution in striation thickness is shifted towards thin striations as the flow rate is increased from below to above the Reynolds numbers of which vortices were first observed, but some striations still pass the mixer elements almost unaffected, which can be seen in the skewness of the distribution of the striation thickness, which shifts from being negative to positive. (c) 2006 Elsevier Ltd. All rights reserved. (Less)
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author
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organization
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publication status
published
subject
keywords
fluid dynamics, computational, secondary flow, static mixer, rate of striation thinning, particle tracking, laminar flow
in
Chemical Engineering Science
volume
61
issue
18
pages
6133 - 6141
publisher
Elsevier
external identifiers
  • wos:000240307200019
  • scopus:33746527378
ISSN
0009-2509
DOI
10.1016/j.ces.2006.05.044
language
English
LU publication?
yes
id
2f17a652-d2e5-4e77-9c8f-5908ea7a6874 (old id 394819)
date added to LUP
2016-04-01 17:07:26
date last changed
2021-08-25 04:46:19
@article{2f17a652-d2e5-4e77-9c8f-5908ea7a6874,
  abstract     = {A method based on computational fluid dynamics (CFD) for the characterization of static mixers using the Z factor, helicity and the rate of striation thinning is presented. These measures were found to be well-suited for the characterization of static mixers as they reflect the pressure drop, the formation of secondary flow, i.e. vortices, and their effect on the mixing process. Two commercial static mixers, the Kenics KM and Lightnin Series 45, have been characterized. In the mixers investigated, secondary flow is formed in the flow at the element intersections and due to the curvature of the mixer elements. The intensity of the vortices is higher in the Lightnin than the Kenics mixer due to edges in the middle of the Lightnin mixer elements. The formation of vortices affects the Z factor by an increase in the power requirement, and the rate of striation thinning by an increase in the stretching of the striations. The formation of vortices was observed at a Reynolds number of 10 in both mixers with aspect ratios of 1.5. However, the intensity of the vortices was greater in the Lightnin than the Kenics mixer, which was observed in not only the magnitude of the helicity, but also the Z factor, rate of striation thinning and the distribution of striation thickness. The distribution in striation thickness is shifted towards thin striations as the flow rate is increased from below to above the Reynolds numbers of which vortices were first observed, but some striations still pass the mixer elements almost unaffected, which can be seen in the skewness of the distribution of the striation thickness, which shifts from being negative to positive. (c) 2006 Elsevier Ltd. All rights reserved.},
  author       = {Regner, Mårten and Östergren, Karin and Trägårdh, Christian},
  issn         = {0009-2509},
  language     = {eng},
  number       = {18},
  pages        = {6133--6141},
  publisher    = {Elsevier},
  series       = {Chemical Engineering Science},
  title        = {Effects of geometry and flow rate on secondary flow and the mixing process in static mixers - A numerical study},
  url          = {http://dx.doi.org/10.1016/j.ces.2006.05.044},
  doi          = {10.1016/j.ces.2006.05.044},
  volume       = {61},
  year         = {2006},
}