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Local levels of dissipation rate of turbulent kinetic energy in a rotor–stator mixer with different stator slot widths—An experimental investigation

Mortensen, Hans Henrik; Innings, Fredrik LU and Håkansson, Andreas LU (2018) In Chemical Engineering Research and Design 130. p.52-62
Abstract

Rotor–stator mixers (RSMs) are widely used for emulsification and mixing. However, relatively little is known about the relationship between RSM design, hydrodynamics and performance. Previous studies have investigated shaft power draw as a function of design. However, power draw alone is not sufficient to predict efficiency. In order to understand the effect on performance it is important to investigate how the local turbulent stress is influenced by design parameters. This study investigates the effect of stator slot width on the local dissipation rate of turbulent kinetic energy using particle image velocimetry coupled with a sub-resolution modeling approach suggested in previous studies. Results are compared to traditional shaft... (More)

Rotor–stator mixers (RSMs) are widely used for emulsification and mixing. However, relatively little is known about the relationship between RSM design, hydrodynamics and performance. Previous studies have investigated shaft power draw as a function of design. However, power draw alone is not sufficient to predict efficiency. In order to understand the effect on performance it is important to investigate how the local turbulent stress is influenced by design parameters. This study investigates the effect of stator slot width on the local dissipation rate of turbulent kinetic energy using particle image velocimetry coupled with a sub-resolution modeling approach suggested in previous studies. Results are compared to traditional shaft power draw measurements and a set of emulsification experiments. It is concluded that wider slots, although requiring less total shaft power, provide a higher maximal (time-averaged) dissipation rate of TKE, which explains why they give rise to more efficient drop breakup. Apparently, more of the power input is transformed into pumping for the narrower slots which leaves less energy for turbulent dissipation. The study illustrates the need for supplementing traditional power draw measurements with local flow characterization in order to better understand the relationship between RSM hydrodynamics and dispersion performance.

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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
Dissipation, Emulsification, Mixing, Particle image velocimetry, Rotor–stator mixer, Turbulence
in
Chemical Engineering Research and Design
volume
130
pages
11 pages
publisher
IChemE
external identifiers
  • scopus:85038640915
ISSN
0263-8762
DOI
10.1016/j.cherd.2017.12.006
language
English
LU publication?
yes
id
f149eb5f-c9a3-46a5-928e-ed68ed8445c6
date added to LUP
2018-01-03 06:47:03
date last changed
2018-05-29 11:51:34
@article{f149eb5f-c9a3-46a5-928e-ed68ed8445c6,
  abstract     = {<p>Rotor–stator mixers (RSMs) are widely used for emulsification and mixing. However, relatively little is known about the relationship between RSM design, hydrodynamics and performance. Previous studies have investigated shaft power draw as a function of design. However, power draw alone is not sufficient to predict efficiency. In order to understand the effect on performance it is important to investigate how the local turbulent stress is influenced by design parameters. This study investigates the effect of stator slot width on the local dissipation rate of turbulent kinetic energy using particle image velocimetry coupled with a sub-resolution modeling approach suggested in previous studies. Results are compared to traditional shaft power draw measurements and a set of emulsification experiments. It is concluded that wider slots, although requiring less total shaft power, provide a higher maximal (time-averaged) dissipation rate of TKE, which explains why they give rise to more efficient drop breakup. Apparently, more of the power input is transformed into pumping for the narrower slots which leaves less energy for turbulent dissipation. The study illustrates the need for supplementing traditional power draw measurements with local flow characterization in order to better understand the relationship between RSM hydrodynamics and dispersion performance.</p>},
  author       = {Mortensen, Hans Henrik and Innings, Fredrik and Håkansson, Andreas},
  issn         = {0263-8762},
  keyword      = {Dissipation,Emulsification,Mixing,Particle image velocimetry,Rotor–stator mixer,Turbulence},
  language     = {eng},
  month        = {02},
  pages        = {52--62},
  publisher    = {IChemE},
  series       = {Chemical Engineering Research and Design},
  title        = {Local levels of dissipation rate of turbulent kinetic energy in a rotor–stator mixer with different stator slot widths—An experimental investigation},
  url          = {http://dx.doi.org/10.1016/j.cherd.2017.12.006},
  volume       = {130},
  year         = {2018},
}