A method for predicting the number of active bubbles in sonochemical reactors
No Thumbnail Available
Date
2015
Journal Title
Journal ISSN
Volume Title
Publisher
Elsevier
Abstract
Knowledge of the number of active bubbles in acoustic cavitation field is very important for the prediction
of the performance of ultrasonic reactors toward most chemical processes induced by ultrasound.
The literature in this field is scarce, probably due to the complicated nature of the phenomena. We introduce
here a relatively simple semi-empirical method for predicting the number of active bubbles in an
acoustic cavitation field. By coupling the bubble dynamics in an acoustical field with chemical kinetics
occurring in the bubble during oscillation, the amount of the radical species _OH and HO_
2 and molecular
H2O2 released by a single bubble was estimated. Knowing that the H2O2 measured experimentally during
sonication of water comes from the recombination of hydroxyl (_OH) and perhydroxyl (HO2
2) radicals in
the liquid phase and assuming that in sonochemistry applications, the cavitation is transient and the bubble
fragments at the first collapse, the number of bubbles formed per unit time per unit volume is then
easily determined using material balances for H2O2, _OH and HO2
2 in the liquid phase. The effect of ultrasonic
frequency on the number of active bubbles was examined. It was shown that increasing ultrasonic
frequency leads to a substantial increase in the number of bubbles formed in the reactor