Dissolution of a Carbon Dioxide Bubble in a Vertical Pipe

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Dissolution of single carbon dioxide (CO2) bubbles in a vertical pipe of 25 mm diameter is measured to examine the effects of the ratio λ of the sphere-volume equivalent bubble diameter to the pipe diameter, the liquid Reynolds number and surfactants on mass transfer. The bubble diameter and liquid Reynolds number are varied from 5.0 to 26 mm (0.20 < λ < 1.0) and from 0 to 3100, respectively. Millipore water, tap water or water contaminated with Triton X-100 are used for the liquid phase. Dissolution processes are measured at atmospheric pressure and room temperature. Mass transfer coefficients and Sherwood numbers are evaluated from measured bubble diameters. Complicated capillary waves are formed at the clean bubble surface, whereas there are no capillary waves at the contaminated bubble surface. The disappearance of capillary wave results in the retardation of surface renewal, and therefore, Sherwood number decreases with increasing surfactant concentration. Empirical correlations of Sherwood numbers for bubbles rising in clean and contaminated liquids in a vertical pipe are proposed. The correlations are applicable not only to bubbles in stagnant liquid but also to bubbles in pipe flow, provided that the liquid Reynolds number is not so high.