Mapping of sonochemical reactors: Review, analysis, and experimental verification

The erratic behavior of cavitational activity, exhibited in a sonochemical reactor poses a serious problem in its design and scale-up. Several previous studies in the past dealt with mapping of sonochemical reactors, which have been critically analyzed and recommended for efficient scale-up strategies. There have been no efforts to link the primary effects (local pressure field) of ultrasound activity with the observed secondary effects (such as chemical reaction). In this work an ultrasonic horn (standard immersion-type reactor), and an ultrasonic bath (rectangular geometry with transducers located at the bottom in triangular pitch) reactors were mapped with the help of local pressure measurement (using a hydrophone), and liberated iodine was estimated using the Weissler reaction, and a quantitative relationship was established between the two. In estimating chemical reaction rates, the effect of microscopic variation in the type of microreactor used (test tube in this case) on the extent of degradation was also investigated. Measured local pressure pulses were used in theoretical simulations of bubble dynamics equations to check the type of cavitation taking place locally, and to estimate the possible collapse of the pressure pulse in terms of the maximum bubble size reached during the cavitation phenomena. A relationship also was established between observed iodine liberation rates and the maximum bubble size reached. The engineers can easily use these unique relationships in an efficient design, since the secondary effect can be directly quantified.