Numerical and experimental investigation of the cavitation field in horn-type sonochemical reactors

Abstract

The implosion of ultrasound-generated bubbles in a liquid medium elicits chemical effects, which accelerate a variety of reactions. However, the relationship between the bubble dynamics and their chemical activity in different cavitation zones of horn-type sonoreactors remains poorly understood. Hence, we applied sonochemiluminescence and KI dosimetry in water at different input powers, probe immersion depths and liquid volume in a custom-designed 20 kHz sonoreactor to measure the sonochemical activity. High-speed imaging revealed that the cavitation bubbles’ number density and size depend on the acoustic pressure and location of the chemically active zones within the ultrasound field. Probe located close to the bottom and moderate power density, 424.29 W/L provided the highest cavitation yield and enhanced oxidation through the creation of an active zone around the neck of the probe. However, the high sonochemical activity around the neck was associated with adverse effects at the tip and below the tip of the probe, which led to a reduction in cavitation yield with a further increase in power. A numerical model predicting the intensity and spatial distribution of the cavitation zones identifies a combination of probe immersion depth and input power to achieve high chemical activity.