Abstract
Bubble formation and bubbling regimes are well-characterized for the cases of single-orifice bubblers and industrial perforated plates. However, bubbling regimes from bubblers with multiple in-line orifices remain poorly described. Here, we investigate the dynamics of bubble formation at both single-orifice and multi-orifice bubblers, with one, three, five and nine in-line orifices in an 80-cm-long bubbler. We use high-speed videography and image processing to identify the effects of bubbler volume, and the number, spacing, and diameter of orifices, on bubbling regimes, bubble period, and bubble formation time. We identify five main bubbling regimes based on synchronization among orifices, and discuss the parameters affecting the bubbling dynamics. Decreasing bubbler volume leads to a decrease in bubble volume and bubble period, and enhances synchronization. Increasing orifice diameter leads to an increase in bubble volume and enhances synchronization. Spacing between orifices doesn't play an important role in determining the bubbling regime. Based on the experimental observations, we develop new bubbling regime maps constructed using the dimensionless Capacitance number and Weber number.
Highlights
Bubble formation plays an important role in many industrial and environmental settings, such as cooling systems, gas absorption units, air-lift reactors, metallurgic processing, and waste-water treatment
We observe the same regimes of bubble formation, as characterized by degree of bubble interaction, as previously described in the literature (e.g., Muller and Prince, 1972; Clift et al, 1978; Badam et al, 2007; Wang et al, 2017)
Experimental observations and measurements from high-speed videography allowed us to constrain the processes involved in bubble formation and the effects on bubbling dynamics of varying number and diameter of orifices, bubbler volume, and gas flow rate: 1) For single-orifice bubblers we extend previous experimental studies to higher gas flow rates, and show that published models for bubble volume as a function of gas flow rate are inadequate for regimes in which the wake of a bubble affects the formation of the bubble
Summary
Bubble formation plays an important role in many industrial and environmental settings, such as cooling systems, gas absorption units, air-lift reactors, metallurgic processing, and waste-water treatment. Various studies have shown that bubble volume, velocity, and bubbling regimes for differing gas flow rates are influenced by properties of the gas phase (e.g., Kumar and Kuloor, 1970; Idogawa, 1987), liquid rheology (e.g., Kumar and Kuloor, 1970; Clift et al, 1978; Jamialahmadi et al, 2001), chamber volume (e.g., Kumar and Kuloor, 1970; Tsuge and Hibino, 1983) and orifice diameter (e.g., Badam et al, 2007; Di Bari and Robinson, 2013). Variations in the chamber volume, together with changes in orifice diameter, dictate bubble volume and frequency; an increase in either of these parameters leads to a bigger bubble volume and increase in frequency
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