Effect of Acoustic Standing Wave in a Bubble Column

Experiments using nickel magnetostrictive oscillators as transducers that generate acoustic standing waves in a bubble column were conducted in this study. The acoustic frequencies employed are 16 and 20 kHz with power up to 400 W. The column is operated at a constant room temperature, with the heat generated from acoustic excitation removed by the use of a water jacket. The study examines the fundamental behavior of initial bubble size, bubble rise velocity and movement of a swarm of mesobubbles (2−8 mm in diameter), gas−liquid mass transfer, and turbulence under the influence of the Bjerknes force in the acoustic field. The results indicate a smaller initial bubble size, a slower bubble rise velocity, and more concentrated bubble aggregates in the presence, rather than in the absence, of the acoustic field. Furthermore, the gas−liquid mass transfer rate and the liquid-phase turbulence are found to be significantly enhanced when an acoustic field is present.