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Influence of Viscosity Ratio on the Mixing Process in a Static Mixer: Numerical Study

Regner, Mårten LU ; Östergren, Karin LU and Trägårdh, Christian LU (2008) In Industrial & Engineering Chemistry Research 47(9). p.3030-3036
Abstract
The mixing process in a Lightnin Series 45 static mixer, 40 mm in diameter, has been investigated using computational fluid dynamics and the volume of fluid (VOF) method, a method developed for immiscible fluids but here used for miscible. The mixing process was investigated for two liquids that had viscosities ranging from 0.003 to 51.2 Pa s, and the volumetric flow rate proportion between the liquids was varied between 1/1 and 4/1. The flow rate was 0.1 m/s, and two Reynolds numbers, 1 and 70, were investigated. The mixer performance was evaluated using the rate of striation thinning, and it was found that the greater the difference in viscosity the worse the mixer performance. This effect is due to the difference in elongation rate... (More)
The mixing process in a Lightnin Series 45 static mixer, 40 mm in diameter, has been investigated using computational fluid dynamics and the volume of fluid (VOF) method, a method developed for immiscible fluids but here used for miscible. The mixing process was investigated for two liquids that had viscosities ranging from 0.003 to 51.2 Pa s, and the volumetric flow rate proportion between the liquids was varied between 1/1 and 4/1. The flow rate was 0.1 m/s, and two Reynolds numbers, 1 and 70, were investigated. The mixer performance was evaluated using the rate of striation thinning, and it was found that the greater the difference in viscosity the worse the mixer performance. This effect is due to the difference in elongation rate between the liquids, which exists until equilibrium in shear stress has been reached at the interface between the liquids. For higher Re numbers close to a point when secondary motions start to have significance for the rate of striation thinning, a lower viscosity of the added liquid results in an increase in mixing performance. It was further found that the VOF method can be used to model the mixing of dissimilar liquids in static mixers, but since the thickness of the striations decreases rapidly with the number of mixer elements, the VOF method is most suitable when investigating mixing processes over a small number of mixer elements. (Less)
Please use this url to cite or link to this publication:
author
organization
publishing date
type
Contribution to journal
publication status
published
subject
in
Industrial & Engineering Chemistry Research
volume
47
issue
9
pages
3030 - 3036
publisher
The American Chemical Society
external identifiers
  • wos:000255466400023
  • scopus:44349192633
ISSN
0888-5885
DOI
10.1021/ie0708071
language
English
LU publication?
yes
id
35662773-70fa-417e-afc8-9cabb4bfa89c (old id 1054338)
date added to LUP
2008-07-11 09:42:01
date last changed
2017-07-09 03:58:15
@article{35662773-70fa-417e-afc8-9cabb4bfa89c,
  abstract     = {The mixing process in a Lightnin Series 45 static mixer, 40 mm in diameter, has been investigated using computational fluid dynamics and the volume of fluid (VOF) method, a method developed for immiscible fluids but here used for miscible. The mixing process was investigated for two liquids that had viscosities ranging from 0.003 to 51.2 Pa s, and the volumetric flow rate proportion between the liquids was varied between 1/1 and 4/1. The flow rate was 0.1 m/s, and two Reynolds numbers, 1 and 70, were investigated. The mixer performance was evaluated using the rate of striation thinning, and it was found that the greater the difference in viscosity the worse the mixer performance. This effect is due to the difference in elongation rate between the liquids, which exists until equilibrium in shear stress has been reached at the interface between the liquids. For higher Re numbers close to a point when secondary motions start to have significance for the rate of striation thinning, a lower viscosity of the added liquid results in an increase in mixing performance. It was further found that the VOF method can be used to model the mixing of dissimilar liquids in static mixers, but since the thickness of the striations decreases rapidly with the number of mixer elements, the VOF method is most suitable when investigating mixing processes over a small number of mixer elements.},
  author       = {Regner, Mårten and Östergren, Karin and Trägårdh, Christian},
  issn         = {0888-5885},
  language     = {eng},
  number       = {9},
  pages        = {3030--3036},
  publisher    = {The American Chemical Society},
  series       = {Industrial & Engineering Chemistry Research},
  title        = {Influence of Viscosity Ratio on the Mixing Process in a Static Mixer: Numerical Study},
  url          = {http://dx.doi.org/10.1021/ie0708071},
  volume       = {47},
  year         = {2008},
}