6533b860fe1ef96bd12c393b

RESEARCH PRODUCT

Bubble formation at variously inclined nozzles

subject

description

Bubble formation at variously inclined submerged nozzles, fed with a continuous gas flow rate, is investigated. Results confirm previous findings, such as a substantial independence of bubble size of nozzle diameter and its dependence on the cubic root of gas flow rate at sufficiently high values of this parameter. Nozzle inclination in the range between 0 and 135° from the vertical upward orientation is found to have a negligible effect on bubble size. Observed bubble rise velocities lead to an estimation of the average liquid velocity induced by bubbles motion, leading in turn to a very simple correlation for the estimation of the liquid velocities induced by the repeated passage of bubbles. An effective model for the prediction of bubble sizes at their detachment from vertical nozzle orifices is finally presented. The model proposed encompasses a bound expansion stage, followed by an accelerated expansion phase, ended by an original bubble detachment criterion. The existence of a liquid phase effective entrainment velocity, generated by the continuous passage of the bubble stream, is quantified and usefully included in the model. Model predictions are found to compare very well with present experimental data, as well as with literature data.