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- Hindered settling
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Hindered settling Chong, Yu Sen
Abstract
Natural and commercially available particles of uniform shape and size were used to study the effect of particle shape on hindered settling in creeping flow (Re₀< 0.1), where fluid flow behaviour is independent of particle Reynolds number and the effect of shape is most prominent. Particles of different shapes used were spherical glass beads, cubic salt (NaCl) crystals and ABS plastic pellets, flaky sugar crystals and angular mineral (silicate) crystals. They were carefully sized by sieving and liquid elutriation to avoid other effects like size segregation. Constant settling data were processed in the form of uѵ rather than u to eliminate the effect of temperature variation on viscosity. The effect of the wall on hindered settling rate was found to be small in most cases. The method proposed by Beranek and Klumpar for correlating fluidization data on different shaped particles was found to be only moderately successful in correlating the present settling data for different shapes. Results were plotted as loguѵ versus log €, and the index n of the equation uѵ/(uѵ)ext = €ⁿ was calculated by least squares. It varied from an average value of 4.8 for the smooth spheres to 5.4 for the cubes to 5.8 for the flaky or angular particles. In contrast to the corresponding term proposed by Richardson and Zaki, the term (uѵ)ext was measurably lower than uѵ for free settling of the spherically isotropic particles. More significantly, the index n was graphically found to display a definite trend with the random loose fixed bed porosity, which is shape dependent and easily measured, and may therefore turn out to be a simple and useful parameter for taking account of shape variation.
Item Metadata
Title |
Hindered settling
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Creator | |
Publisher |
University of British Columbia
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Date Issued |
1968
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Description |
Natural and commercially available particles of uniform shape and size were used to study the effect of particle shape on hindered settling in creeping flow (Re₀< 0.1), where fluid flow behaviour is independent of particle Reynolds number and the effect of shape is most prominent. Particles of different shapes used were spherical glass beads, cubic salt (NaCl) crystals and ABS plastic pellets, flaky sugar crystals and angular mineral (silicate) crystals. They were carefully sized by sieving and liquid elutriation to avoid other effects like size segregation. Constant settling
data were processed in the form of uѵ rather than u to eliminate the effect of temperature variation on viscosity.
The effect of the wall on hindered settling rate was found to be small in most cases. The method proposed by Beranek and Klumpar for correlating fluidization data on different shaped particles was found to be only moderately successful in correlating the present settling data for different
shapes.
Results were plotted as loguѵ versus log €, and the index n of the equation uѵ/(uѵ)ext = €ⁿ was calculated by least squares. It varied from an average value of 4.8 for the smooth spheres to 5.4 for the cubes to 5.8 for the flaky or angular particles. In contrast to the corresponding term proposed by Richardson and Zaki, the term (uѵ)ext was measurably
lower than uѵ for free settling of the spherically isotropic
particles. More significantly, the index n was graphically found to display a definite trend with the random loose fixed bed porosity, which is shape dependent and easily measured,
and may therefore turn out to be a simple and useful parameter
for taking account of shape variation.
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Genre | |
Type | |
Language |
eng
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Date Available |
2011-06-09
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Provider |
Vancouver : University of British Columbia Library
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Rights |
For non-commercial purposes only, such as research, private study and education. Additional conditions apply, see Terms of Use https://open.library.ubc.ca/terms_of_use.
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DOI |
10.14288/1.0059107
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URI | |
Degree | |
Program | |
Affiliation | |
Degree Grantor |
University of British Columbia
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Campus | |
Scholarly Level |
Graduate
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Aggregated Source Repository |
DSpace
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Item Citations and Data
Rights
For non-commercial purposes only, such as research, private study and education. Additional conditions apply, see Terms of Use https://open.library.ubc.ca/terms_of_use.