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Effect of scale‐up on wall shear rates in circulating bubble columns
Author(s) -
AlMasry Waheed A,
AlAhmed Malik I
Publication year - 2005
Publication title -
journal of chemical technology and biotechnology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.64
H-Index - 117
eISSN - 1097-4660
pISSN - 0268-2575
DOI - 10.1002/jctb.1309
Subject(s) - bubble , shear rate , carboxymethyl cellulose , newtonian fluid , shear (geology) , dispersion (optics) , mechanics , non newtonian fluid , xanthan gum , materials science , chemistry , shear thinning , thermodynamics , volume (thermodynamics) , rheology , chromatography , composite material , physics , optics , organic chemistry , sodium
Effective wall shear rates were investigated experimentally in an external loop circulating bubble column made from transparent acrylic resin. The riser ( D R ) and downcomer ( D D ) diameters were 0.19 m and 0.14 m, respectively. The column working volume ( V R ) was 170 dm 3 , with a scale‐up factor ( A D / A R ) of 0.54, and a dispersion height ( H D ) of 2.25 m. Polymer solutions of xanthan gum and carboxymethyl cellulose were used to simulate non‐Newtonian behavior of biological systems. Effective wall shear rates for the non‐Newtonian solutions were found by analogy with Newtonian glycerol solutions, employing downcomer liquid velocity as the measurable and comparable parameter. The experimental shear rate results were found to fit between those of the literature data. A new single correlation taking into account all the relevant data in the literature and the results of this work is proposed. The new correlation is an improvement over the other correlations because it includes two important design constants: scale‐up factor and dispersion height. Copyright © 2005 Society of Chemical Industry