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Estimation of agitator flow shear rate
Author(s) -
Wu Jie,
Graham Lachlan J.,
Noui Mehidi Nabil
Publication year - 2006
Publication title -
aiche journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.958
H-Index - 167
eISSN - 1547-5905
pISSN - 0001-1541
DOI - 10.1002/aic.10857
Subject(s) - agitator , impeller , shear rate , mechanics , shear (geology) , shear flow , newtonian fluid , volumetric flow rate , shear thinning , rheometer , materials science , viscosity , thermodynamics , physics , rheology , composite material
Laboratory laser Doppler velocimetry (LDV) measurements were conducted to measure the shear rate coefficient K S of a range of impellers. Equations correlating K S with N Q (flow number) are provided for axial flow and radial flow impellers. Theoretical formulations based on the classic boundary layer theory are developed to estimate the shear rate at the blade surface. Calculations show that the shear rates at the blade surface are many orders of magnitude higher than those in the flow at the impeller outlet. The software code XFOIL was used to illustrate typical distributions of the shear rates along the blade surfaces. Effects of viscosity, non‐Newtonian shear‐thinning index, agitator design, and scale‐up on shear rates are illustrated. © 2006 American Institute of Chemical Engineers AIChE J, 2006