Homogeneous Bubble Flow Regime

In view of the fact that chains of bubbles are formed, this regime is sometimes referred to as chain bubbling regime. The terminal rise velocity of a small discrete bubble is relatively very low. However, the drag on an individual bubble is affected by the presence of bubbles in its vicinity. The resulting hindrance increases with inaeasing number of bubbles or gas holdup. The drag and consequent turbulence is 

FIGURE 10.1 Approximate dependence of flow regime on column diameter and superficial gas velocity for water and dilute aqueous solutions. (Reproduced from Shah et al. 1982 with permission from John Wiley Sons, Inc. Copyright 1982 American Institute of Chemical Engineers.) 

Typical industrial applications that conform to the homogeneous regime are (Shaikh and Al-Dahhan 2007) cultivation of bacteria and molds/fungi, production of single-cell protein, sewage treatment, and some specific cases of animal cell culture. Hydrotreatment of heavy fractions and coal to hydrocarbon conversion are some application relevant to the chemical industry. 

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Of interest is a recent theoretical relation for eg in gas-liquid bubble columns based on liquid circulation and claimed to be valid both in the homogeneous bubble flow regime and in the chum-turbulent regime, also for non-Newtonian fluids. For power law fluids with... 

In the homogeneous bubble flow regime, the gas phase is generally assumed to move in plug flow and the liquid phase axial mixing is characterized by the axial dispersion coefficient. The axial dispersion coefficient is dependent upon gas velocity and column diameter according to (26,41,42)... 

Vertical Downflow Mode hi the case of vertical downflow, only the coaxial and homogeneous bubbly flow regimes have been reported (Ben Brahim et al. 1984 Bhutada and Pangarkar 1987 Panchal et al. 1991). 

Since an averaging of physical properties is used, such models are further restricted to the post- mixing shock homogeneous bubble flow regime. 

For zones 2-3, besides neglecting the potential energy component, the following assumptions were made (i) the secondary fluid is an ideal gas and the primary fluid is incompressible (ii) at point 2, the flow is in the homogeneous bubble flow regime, and the flow properties can be represented by weighted mixture properties ... 

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