Abstract
Bubble flow is present in many processes that are the subject of chemical engineering research. Many correlations for determination of the equivalent bubble diameter can be found in the scientific literature. However, there are only few describing the formation of gas bubbles in flowing liquid. Such a phenomenon occurs for instance in airlift apparatuses. Liquid flowing around the gas bubble creates a hydraulic drag force that leads to reduction of the formed bubble diameter. Usually the value of the hydraulic drag coefficient, cD, for bubble formation in the flowing liquid is assumed to be equal to the drag coefficient for bubbles rising in the stagnant liquid, which is far from the reality. Therefore, in this study, to determine the value of the drag coefficient of bubbles forming in flowing liquid, the diameter of the bubbles formed at different liquid velocity was measured using the shadowgraphy method. Using the balance of forces affecting the bubble formed in the coflowing liquid, the hydraulic drag coefficient was determined. The obtained values of the drag coefficient differed significantly from those calculated using the correlation for gas bubble rising in stagnant liquid. The proposed correlation allowed the determination of the diameter of the gas bubble with satisfactory accuracy.
Highlights
Multiphase flows are omnipresent in the chemical engineering processes [1]
The objective of this study was, to clarify discrepancies found in the literature related to gas bubble formation in the flowing Newtonian liquid
That even very low liquid flow velocity bubbles formed in thethe coflowing liquid was derived
Summary
Multiphase flows are omnipresent in the chemical engineering processes [1]. One example of the multiphase flow is the flow of gas through a liquid layer. When the gas flow rate is high enough so that a large number of gas bubbles simultaneously flows through the liquid, such a process is known as bubbling. The use of this phenomenon is crucial in many fields, including chemical and process engineering, bioprocess engineering, environmental engineering, and wastewater treatment. A classic example of the bubbling application can be seen in microbiological sewage treatment [2,3,4]. Typical apparatuses employing the phenomenon of bubbling are bubble column [5]
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