Loading…

Investigations on the Stability of the Flow Characteristics in a Bubble Column

The role of the lift force in the stability of the homogeneous flow regime in a bubble column is investigated. Instabilities caused by the lift force may be one important reason for the transition from a homogeneous to a heterogeneous bubble column. The lift force acts on rising bubbles in a lateral...

Full description

Saved in:
Bibliographic Details
Published in:Chemical engineering & technology 2006-09, Vol.29 (9), p.1066-1072
Main Authors: Lucas, D., Krepper, E., Prasser, H.-M., Manera, A.
Format: Article
Language:English
Subjects:
Citations: Items that this one cites
Items that cite this one
Online Access:Get full text
Tags: Add Tag
No Tags, Be the first to tag this record!
Description
Summary:The role of the lift force in the stability of the homogeneous flow regime in a bubble column is investigated. Instabilities caused by the lift force may be one important reason for the transition from a homogeneous to a heterogeneous bubble column. The lift force acts on rising bubbles in a lateral direction when gradients of the liquid velocity are present. Such gradients may result from circulation cells in the bubble column as well as from local disturbances. Depending on the sign of the lift force, such local disturbances in a homogeneous flow may be damped or enhanced. The corresponding feedback mechanism was analyzed by means of linear stability analyses. As a result, criteria for stability were obtained for mono‐dispersed flow, for a flow with two bubble size groups, and, finally, with some additional approximations also for the case of N bubble size groups or a given bubble size distribution. In a next step, the effects were investigated by CFD calculations. The obtained criteria for stability fit well with the observed effects in CFD simulations. Recently, two different groups confirmed the stability criteria experimentally. Instabilities caused by the lift force may be important in the transition from homogeneous to heterogeneous regimes in a bubble column. From linear stability analyses, criteria for stability dependent on the bubble size or bubble size distribution are obtained.
ISSN:0930-7516
1521-4125
DOI:10.1002/ceat.200600150