Churn turbulent two-bubble class

A Two-Bubble Class Model for Churn Turbulent Bubble Column Slurry Reactor... 

Hence, the gas phase conversion for a pseudo-first order reaction in the churn turbulent regime can be calculated if the fractional gas holdups, rise velocities, and interfacial areas for the two bubble classes as well as the physicochemical data are known. 

The two bubble class model is applied here to the absorption of CO2 in NaOH, which conforms to a fast pseudo-first order reaction under certain operating conditions (15). In the data reported by Schumpe et al. ( 7 ), COo was absorbed during cocurrent flow in NaOH solution in a 0.102 m diameter bubble column. The gas phase consisted of approximately 10 vol % of CO2 in N2. The gas velocities ranged from 0.025 to 0.15 m/s. Since the churn turbulent regime prevailed for gas velocities greater than approximately 0.07 m/s, only the data in the range 0.07 m/s to 0.15 m/s were considered. 

The existence of different bubble classes in churn-turbulent flow can be shown easily by dynamic gas disengagement measurements. Simplified evaluation of such measurements yields a splitting of the bubble phase into two bubble classes, i.e., one class of small bubbles with low rise velocity and another class of large bubbles with high rise velocity. Two bubble classes with such properties were also the starting point of a BCR model proposed by Joseph and Shah [41]. Experimental techniques and devices are now available to measure the entire bubble spectrum with regard to size and rise velocity. This information could form the basis of more realistic models of the gas phase flow in BCR. 

Joseph, S. and Y.T. Shah. A Two-Bubble Class Model for Churn Turbulent Bubble Column Slurry Reactors. ACS Symp. Series 27 (1984) 149-167. 

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