Enhanced mixing of newtonian fluids in a stirred vessel using impeller speed modulation

Yek, W, Nouimehidi, M, Parthasarathy, R, Wu, J, Bhattacharya, S, Ohmura, N and Nishioka, N 2009, 'Enhanced mixing of newtonian fluids in a stirred vessel using impeller speed modulation', Canadian Journal of Chemical Engineering, vol. 87, pp. 839-846.


Document type: Journal Article
Collection: Journal Articles

Title Enhanced mixing of newtonian fluids in a stirred vessel using impeller speed modulation
Author(s) Yek, W
Nouimehidi, M
Parthasarathy, R
Wu, J
Bhattacharya, S
Ohmura, N
Nishioka, N
Year 2009
Journal name Canadian Journal of Chemical Engineering
Volume number 87
Start page 839
End page 846
Total pages 8
Publisher John & Wiley Sons, Inc
Abstract This paper reports on an experimental study of mixing intensification using speed modulation of a six-blade Rushton turbine in a stirred vessel. Mixing times were measured using a non-intrusive technique based on direct visualisation of an acid-base reaction in a Newtonian fluid. The impeller speed modulation was achieved by using two waveforms: a square wave and a sine wave. The amplitude was fixed between a maximum Reynolds number of Remax = 60 and minimum Reynolds numbers of Remin = 40 or 30. The wave periods were varied (10, 20, or 40 s) in order to compare the effects of unsteady stirring on mixing performance. It was observed that a square wave protocol with the shortest wave period and the larger amplitude resulted in the shortest time to destroy the observed isolated mixing regions (IMRs), which are known to exist in stirred vessels operating at low Reynolds number. However, the sine wave protocol led to a slow diffusive mechanism in which IMR structures reached an asymptotic volume and remained visible even after several hours. The results are presented and discussed using digital photographs taken at different time intervals during experimentation.
Subject Chemical Engineering Design
Keyword(s) mixing tanks
isolated mixing regions (lMRs)
speed modulation
Newtonianfluids
DOI - identifier 10.1002/cjce.20231
ISSN 00084034
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