6. Intensification techniques under development

6.1 Ultrasound

The application of ultrasonic waves in the vicinity of a heat exchange surface causes disturbances on different scales, depending on the frequency and power applied [AF 6 310] . These effects range from simple propagation, with heating of the fluid due to absorption of the waves, to nebulization of the fluid due to the ultrasonic fountain effect. Between these two extremes, the formation of cavitation bubbles or recirculation cells intensifies heat transfer