Measurement and analysis of small bubble size distributions

Abstract Bubble size distributions were measured at different depths in a 1 m diameter by 2 m length column cell test rig fitted with Cominco spargers. A population balance model has been used to describe the distributions over the length of the column cell and to investigate the extent to which bubble coalescence occurs. The model adequately predicts the mean bubble size and the bubble size distribution due to bubble growth only, at positions up to 40 cm above the point of injection. The model is based upon a coalescence efficiency and variable relative velocities of the coalescing bubbles, and it was found that a constant coalescence efficiency was applicable for small bubble size distributions. The deviations from the model at points further up the column indicates that the coalescence mechanism described by the model is not adequate for large bubble size distributions which behave differently from small bubble size distributions.