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Effect of scale‐up on average shear rates for aerated non‐Newtonian liquids in external loop airlift reactors
Author(s) -
AlMasry Waheed A.
Publication year - 1999
Publication title -
biotechnology and bioengineering
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.136
H-Index - 189
eISSN - 1097-0290
pISSN - 0006-3592
DOI - 10.1002/(sici)1097-0290(19990220)62:4<494::aid-bit14>3.0.co;2-6
Subject(s) - airlift , mechanics , shear rate , non newtonian fluid , shear (geology) , shear thinning , newtonian fluid , bubble , chemistry , rheology , materials science , thermodynamics , chromatography , composite material , physics , bioreactor , organic chemistry
Average shear rates have been estimated experimentally in a 700‐dm 3 external loop airlift reactor. Aqueous pseudoplastic carboxymethylcellulose and xanthan gum solutions were used to simulate non‐Newtonian behavior of biological media. Average shear rates of non‐Newtonian solutions were found by analogy with Newtonian glycerol solutions using downcomer liquid velocity as the measurable parameter. Due to the complexity of local shear rate measurement, an average shear rate was assumed to exist and is proportional to superficial gas velocity. The data from this work and those in the literature were used in producing a new correlation for estimating average shear rates as a function of superficial gas velocity, geometry, and dispersion height. Wall shear rates were found to be significant. The ratio of wall shear rates to bulk shear rates were varied from 5% to 40%. Furthermore, it has been found that shear rates generated in airlift loop reactors are lower than those generated in bubble columns. © 1999 John Wiley & Sons, Inc. Biotechnol Bioeng 62: 494–498, 1999.