Date of Award

1991

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

First Advisor

Richard G. Rice

Abstract

There exists a narrow operating window in bubble columns where the motion is so gentle that the normally dominating forces of coalescence and breakup no longer define column conditions. This behavior is synonymous with operation in the bubbly flow regime. During experimentation, two distinct hydrodynamic regions were observed; close to the sparger, the liquid was well mixed, whilst in the remainder of the column a dispersive flow model was determined to be appropriate. In the entrance zone, the isotropic turbulence theories of Kolmogoroff adequately represented transport behavior. This finding implies that a churn-turbulent environment, wherein bubbles are continuously reformed, will provide optimum transfer rates. Elementary force balances are presented to predict bubble size, rise velocity and interfacial area, which correlate favorably with experimental data. The interfacial area was measured using the chemical method, specifically via the sulphite reaction, for which an innovative mechanistic model was developed. In addition a new theory to predict liquid circulation was derived and compared with applicable literature data. This latter analysis enabled voidage predictions to be made from a modified drift flux approach. It is also argued that liquid circulation holds the key to predicting the experimental values found for axial dispersion. This research highlights the application of a fundamental approach to predict column parameters. Such procedure allowed column performance in the bubbly flow regime to be explained with a coherent theme. Furthermore, bubbly flow is shown to possess the unique characteristics of low stress and dispersion (whilst maintaining adequate transfer rates) ideal for biochemical applications.

Pages

519

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