Effect of geometry on the mechanisms for off-bottom solids suspension in a stirred tank

Inci Ayranci; Marcio B. Machado; Adam M. Madej; J. J. Derksen; David S. Nobes; Suzanne M. Kresta

doi:10.1016/j.ces.2012.05.028

Effect of geometry on the mechanisms for off-bottom solids suspension in a stirred tank

Inci Ayranci^*, Marcio B. Machado, Adam M. Madej, J. J. Derksen, David S. Nobes, Suzanne M. Kresta

^*Corresponding author for this work

Engineering

University of Alberta

Research output: Contribution to journal › Article › peer-review

64 Citations (Scopus)

Abstract

This paper probes solids suspension mechanisms in stirred tanks. The hypothesis is that at the point where solids are just suspended a critical flow condition exists close to the bottom of the tank for a fixed solids content and similar geometries. The critical flow condition may be dominated by the turbulence or by the mean flow. Two Lightnin A310 impellers with diameters of D=T/3 and D=T/2 were tested at varying off-bottom clearances. The mean and the turbulent fluctuating velocities close to the bottom of the tank were determined using both Ply and LES. The results showed that the mechanism of solids suspension is different for the two impeller diameters. Turbulence is the dominant mechanism for the T/3 impeller. For the T/2 impeller some combination of turbulence and mean flow is required. A comparison between the two impeller diameters in terms of power consumption suggests that solids suspension is more efficient when the turbulence mechanism dominates. (C) 2012 Elsevier Ltd. All rights reserved.

Original language	English
Pages (from-to)	163-176
Number of pages	14
Journal	Chemical Engineering Science
Volume	79
Early online date	30 May 2012
DOIs	https://doi.org/10.1016/j.ces.2012.05.028
Publication status	Published - 10 Sept 2012

Bibliographical note

Acknowledgments
The authors would like to thank Lightnin, NSERC, and CNPq, Brazil, for funding this research.

Keywords

Solids suspension mechanisms
Multiphase flow
Turbulence
Mean flow
Impeller diameter
Mixing
PITCHED-BLADE
AGITATED VESSELS
PARTICLES
FLOW
CLEARANCE
IMPELLERS
TURBINE
SPEED

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title = "Effect of geometry on the mechanisms for off-bottom solids suspension in a stirred tank",

abstract = "This paper probes solids suspension mechanisms in stirred tanks. The hypothesis is that at the point where solids are just suspended a critical flow condition exists close to the bottom of the tank for a fixed solids content and similar geometries. The critical flow condition may be dominated by the turbulence or by the mean flow. Two Lightnin A310 impellers with diameters of D=T/3 and D=T/2 were tested at varying off-bottom clearances. The mean and the turbulent fluctuating velocities close to the bottom of the tank were determined using both Ply and LES. The results showed that the mechanism of solids suspension is different for the two impeller diameters. Turbulence is the dominant mechanism for the T/3 impeller. For the T/2 impeller some combination of turbulence and mean flow is required. A comparison between the two impeller diameters in terms of power consumption suggests that solids suspension is more efficient when the turbulence mechanism dominates. (C) 2012 Elsevier Ltd. All rights reserved.",

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author = "Inci Ayranci and Machado, {Marcio B.} and Madej, {Adam M.} and Derksen, {J. J.} and Nobes, {David S.} and Kresta, {Suzanne M.}",

note = "Acknowledgments The authors would like to thank Lightnin, NSERC, and CNPq, Brazil, for funding this research.",

year = "2012",

month = sep,

day = "10",

doi = "10.1016/j.ces.2012.05.028",

language = "English",

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TY - JOUR

T1 - Effect of geometry on the mechanisms for off-bottom solids suspension in a stirred tank

AU - Ayranci, Inci

AU - Machado, Marcio B.

AU - Madej, Adam M.

AU - Derksen, J. J.

AU - Nobes, David S.

AU - Kresta, Suzanne M.

N1 - Acknowledgments The authors would like to thank Lightnin, NSERC, and CNPq, Brazil, for funding this research.

PY - 2012/9/10

Y1 - 2012/9/10

N2 - This paper probes solids suspension mechanisms in stirred tanks. The hypothesis is that at the point where solids are just suspended a critical flow condition exists close to the bottom of the tank for a fixed solids content and similar geometries. The critical flow condition may be dominated by the turbulence or by the mean flow. Two Lightnin A310 impellers with diameters of D=T/3 and D=T/2 were tested at varying off-bottom clearances. The mean and the turbulent fluctuating velocities close to the bottom of the tank were determined using both Ply and LES. The results showed that the mechanism of solids suspension is different for the two impeller diameters. Turbulence is the dominant mechanism for the T/3 impeller. For the T/2 impeller some combination of turbulence and mean flow is required. A comparison between the two impeller diameters in terms of power consumption suggests that solids suspension is more efficient when the turbulence mechanism dominates. (C) 2012 Elsevier Ltd. All rights reserved.

AB - This paper probes solids suspension mechanisms in stirred tanks. The hypothesis is that at the point where solids are just suspended a critical flow condition exists close to the bottom of the tank for a fixed solids content and similar geometries. The critical flow condition may be dominated by the turbulence or by the mean flow. Two Lightnin A310 impellers with diameters of D=T/3 and D=T/2 were tested at varying off-bottom clearances. The mean and the turbulent fluctuating velocities close to the bottom of the tank were determined using both Ply and LES. The results showed that the mechanism of solids suspension is different for the two impeller diameters. Turbulence is the dominant mechanism for the T/3 impeller. For the T/2 impeller some combination of turbulence and mean flow is required. A comparison between the two impeller diameters in terms of power consumption suggests that solids suspension is more efficient when the turbulence mechanism dominates. (C) 2012 Elsevier Ltd. All rights reserved.

KW - Solids suspension mechanisms

KW - Multiphase flow

KW - Turbulence

KW - Mean flow

KW - Impeller diameter

KW - Mixing

KW - PITCHED-BLADE

KW - AGITATED VESSELS

KW - PARTICLES

KW - FLOW

KW - CLEARANCE

KW - IMPELLERS

KW - TURBINE

KW - SPEED

U2 - 10.1016/j.ces.2012.05.028

DO - 10.1016/j.ces.2012.05.028

M3 - Article

SN - 0009-2509

VL - 79

SP - 163

EP - 176

JO - Chemical Engineering Science

JF - Chemical Engineering Science

ER -

Effect of geometry on the mechanisms for off-bottom solids suspension in a stirred tank

Abstract

Bibliographical note

Keywords

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