In situ characterisation of size distribution and rise velocity of microbubbles by high-speed photography

Abstract

Using microbubbles has gained significant interest in many domestic and industrial applications due to bubble stability in solution and increased mass transfer area. The characterisation of microbubble populations is therefore important and aids in the understanding of their behaviour. Microbubble characterisation remains challenging, particularly at high bubble densities. We have developed an in situ and automated method, based on image analysis, to determine bubble size distributions and bubble rise velocity at bubble densities of up to approximately 7 bubbles mm−2. The method uses image analysis of a side-stream viewing slit and was tested using air bubbles in water at diameters between 20 and 150 µm under a range of different conditions. The developed system enables fast, simple and accurate size determination for microbubbles, including continuous sampling and observation.