Resonant Ultrasonic Defoaming in Aqueous Evaporation/Boiling Processes at Different Size Scales

Unwanted foam bears the risk of affecting different thermal industrial processes negatively, by reduced process efficiency, contamination, and total shutdown. Mechanical defoaming methods are difficult to implement, while chemical anti-foaming agents are challenging in correct dosing. Ultrasonic defoaming actuators destroy foams purely mechanically from air-borne, but their energy consumption per area is still excessive at 10 W cm(-2). Results show that a frequency sweep between 40-168 kHz and a water-borne sonication needs power densities of around 0.1 W cm(-2) for a lab-scale experiment to a copper column still. At this power level, ultrasound enforces the foam drainage, thus reducing the foam height and the process time of the column still by 20 %. The chosen frequency range indicates a resonant behavior of small liquid-loaded lamella and plateau channels.