Abstract
Recently, the number of uses of bubbles has begun to increase dramatically, with medicine, biofuel production, and wastewater treatment just some of the industries taking advantage of bubble properties, such as high mass transfer. As a result, more and more focus is being placed on the understanding and control of bubble formation processes and there are currently numerous techniques utilized to facilitate this understanding. Acoustic bubble sizing (ABS) and laser scattering techniques are able to provide information regarding bubble size and size distribution with minimal data processing, a major advantage over current optical-based direct imaging approaches. This paper demonstrates how direct bubble-imaging methods can be improved upon to yield high levels of automation and thus data comparable to ABS and laser scattering. We also discuss the added benefits of the direct imaging approaches and how it is possible to obtain considerable additional information above and beyond that which ABS and laser scattering can supply. This work could easily be exploited by both industrial-scale operations and small-scale laboratory studies, as this straightforward and cost-effective approach is highly transferrable and intuitive to use.
Highlights
Over recent years the use of microbubbles in commercial applications has attracted major interest in areas such as medical imaging, drug delivery, algal growth, biofuel production, and emulsion separation
Microbubble images were analyzed using custom-made Laboratory Virtual Instrument Engineering Workbench (LabVIEW) software, details of which are discussed in detail in the preceding paper and are available to download according to Code 1, Ref. [31], Code 2, Ref. [32], and Code 3, Ref. [33] below
This study has shown how an optical characterization system may be established and utilized to bring the previously tedious optical analysis of bubble clouds to a level of automation previously seen in other high-cost systems such as Acoustic bubble sizing (ABS) and laser scattering
Summary
Over recent years the use of microbubbles in commercial applications has attracted major interest in areas such as medical imaging, drug delivery, algal growth, biofuel production, and emulsion separation. This has led to a requirement for a deeper understanding of the bubble formation process. Microbubble generation by a robust technique, such as the fluidic oscillator systems presented by Zimmerman and Tesař [15,16,17,18], have proven to be a breakthrough in energy-efficient separation Tailoring conditions such as flow rate, pressure, and frequency, the bubble size can be tuned to meet the specific needs of each individual system. There are numerous characterization techniques available, with several briefly reviewed here
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