Bubble formation from sub-millimeter orifices under variable gas flow conditions

• Published in: Chemical engineering science Vol. 242; p. 116698
• Main Authors: Mohseni, E., Ziegenhein, T., Reinecke, S.F., Hampel, U.
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 12.10.2021
• Subjects: Bubble dynamics; Bubble formation; Gas reservoir; Sub-millimeter orifice; Bubble dynamics; Bubble formation; Gas reservoir; Sub-millimeter orifice
• ISSN: 0009-2509; 1873-4405
• DOI: 10.1016/j.ces.2021.116698

•The gas reservoir upstream of an orifice affects the bubble formation dynamics.•Enlarging the gas reservoir results in the formation of larger bubbles.•Influence of the gas reservoir can be characterized using the capacitance number.•The critical capacitance number for a gas reservoir depends on the orifice size.•Besides the gas flow rate, the bubbling regime depends on the gas reservoir volume. We provide an experimental investigation on the mechanism of the bubble formation from sub-millimeter orifices under variable gas flow conditions VGFC. The effect of influential parameters including the volumetric gas flow rate Q, the orifice diameter dor, and the volume of the gas reservoir Vc upstream of the orifice are investigated in detail. We found that, by enlarging Vc,q increases. This affects various aspects of bubble formation dynamics such as the bubble base expansion, the apparent contact angle at the three-phase contact point, and the bubble detachment criterion. The effect of Vc is best presented by its dimensionless group, the capacitance number Nc. The minimum Nc from which the influence of the gas reservoir becomes important depends on the orifice size. Moreover, a significant increase in Vc leads to a change in the bubbling regime towards multiple bubble formation.