Abstract:The influence of gas flow rates and nozzle diameters on bubble size and aspect ratio distributions was studied using high-speed photography with an image processing algorithm. Results reveal bimodal probability density distributions (PDD) of bubble diameter under all nozzle diameters, with one peak near 1.5-2 mm and the another in the larger bubble range. Increasing gas flow rates from 0.1 to 0.2 L/min leads to a higher probability density of large bubbles, indicating prevalent bubble coalescence. As the gas flow rate rises to 1.2 L/min, the peak shifts to smaller bubble diameters, and the bubble breakage becomes dominant. For 1-2 mm bubbles, shape is less influenced by gas flow rates, while 3-9 mm bubbles exhibit aspect ratio PDD peaks at an aspect ratio (E) of 0.5 across all gas flow rates. The Iguchi and Chihara model can better predict the variation of bubble departure diameter with increasing gas flow rates.

Key words: bubble size distribution; bubble diameter; bubble aspect ratio; gas flow rate; nozzle diameter; bubble column