Abstract
Bubble columns are used in various industrial plants: e.g. chemical plants, bioreactors, wastewater treatments and so on. Bubbly flows in the bubble columns fluctuate in time and space. The flow structures in the bubbly flows should be considered in order to achieve the safety operation and high mass transfer rate of the bubble columns. Few researchers, however, clarified the flow structures and the mass transfer mechanisms in the flows. One of the major problems is that researchers currently possess no instrument to simultaneously measure the bubble characteristics and local solution concentration. In the present study, we overcame this problem by developing a new optical fiber probe (POFP) and will clarify the relationship between the flow structures and mass transfer mechanism. The time-series void fractions, local CO_2 concentration and liquid-phase velocities were simultaneously measured by using the POFP and Laser Doppler Velocimeter (LDV). We calculated the spatial scale of the bubble swarms and liquid-phase motion based on the thinking of the integral length scale. As a result, the spatial scale of the bubble swarms and liquid-phase motion have changed by height. Moreover, the liquid-phase flows were not isotropic around the center of the column. The liquid-phase flows appeared to be isotropic in a region near the wall.
