The effects of twisted fin baffles on the microbubble formation from a venturi-type microbubble generator

Abstract

The venturi-type MBG with twisted fin baffles was evaluated in terms of average bubble size, size of bubble distribution, and coefficient of volumetric oxygen mass transfer. The distribution of bubble size and the average bubble size were acquired through an image processing technique applied to microbubble images captured with a high-speed video camera. The volumetric oxygen mass transfer coefficient was determined using a dynamic physical absorption model. This study presents a performance comparison of the venturi-type MBG with and without twisted fin baffles. This study presents a performance comparison of the venturi-type MBG with and without twisted fin baffles. The findings indicate that the venturi-type MBG with twisted fin baffles generates a smaller average bubble diameter and obtains a more uniform bubble size distribution than the configuration without baffles. The venturi-type MBG with twisted fin baffles demonstrates a higher volumetric oxygen mass transfer coefficient than the configuration without baffles. It was concluded that the venturi-type MBG with twisted fin baffles is more effective in microbubble formation. Subsequently, empirical correlations for average bubble size, distribution of bubble size, and coefficient of volumetric oxygen mass transfer were developed through dimensional analysis, in which liquid and gas Reynolds numbers play crucial roles.