A New Theory to Explain Transport in Pulsed-Flow Bubble Columns: the Bjerknes Effect
Yogesh Waghmare, F.Carl Knopf, and Richard G. Rice. Chemical Engineering, Louisiana State University, Dept. of Chemical Engineering, LSU, Baton Rouge, LA 70803
New experimental data for a range of gas velocities from 0.1 to 1.5 cm/s are explained by an elementary theory which combines the effect of bubble retardation owing to Bjerknes forces with the breakage relationship of Hinze. The theory predicts experimental voidage very closely without parameter adjustment for a frequency range from 10 to 30 Hz. Two amplitudes of fluid oscillation were used in the 8.9 cm column: 1.66 and 2.46 mm. Experimental values of volumetric mass transfer coefficient for oxygen dissolution followed predictions of theory when the constant multiplier was adjusted in the modified penetration theory. A new phenomenon was observed and was predictable from theory, namely, “flooding”, which arises when all bubbles are fully retarded or move downward. Under flooding conditions, transport enhancement ceases as frequency or amplitude is increased.