(234f) Fundamentals of Bubble Transport in an Ultrasonically Assisted Separation Process

The use of ultrasonic fields to induce phase separations of a dispersed solid, immiscible liquid, or gas within a suspending liquid phase has received increasing attention over the past two decades. Dissolved and entrained gases, and thus gas bubbles, have the potential to produce transport inefficiencies in closed-loop flow systems and also have the possibility of causing materials failure. Research conducted in this study investigates the applicability of the use of a resonant ultrasonic wave field to entrap and harvest gas bubbles from a surrounding liquid. By subjecting the bubbles to a standing acoustic field, their migration and coalescence can be managed, allowing for ease of removal. Current techniques for gas-liquid separations include static separators, which can be prone to fouling; vortex separators, which are not suited for low flow; and rotary separators, which tend to be mechanically complex and expensive. This research aims to develop a fundamental understanding of the effect of forces induced by resonant ultrasonic fields on the on the entrapment and coalescence phenomena. Modeling efforts illustrate the relationship between the size of bubbles, their sphericity, acoustic field parameters (frequency and intensity), bubble placement relative to acoustic pressure antinodes, and the bubble coalescence phenomena. Experiments involving small numbers of bubbles (less than ten) are used to test the basic predictions of the model. These results support subsequent studies of the coalescence of swarms of bubbles. Results will be compared to information obtained from literature.