Experimental Investigation of High-Frequency, High-Intensity Ultrasonics for Thermal Destratification of Liquids Stored in Insulated Containers: Effect of Storage Pressure
T.K. Jagannathan, Srijith Mohanan and R. Nagarajan
The application of power ultrasound for destratification of thermal layers setup in insulated storage containers was investigated experimentally. Coupling of ultrasound with liquid medium produces acoustic cavitation and acoustic streaming. These two events are responsible for all physicochemical transformations taking place within an ultrasonic system. The effect of storage pressure on destratification with the application of ultrasonics was studied experimentally. Increase in storage pressure shows contrasting effects at low and high frequency of applied acoustic field. Destratification is faster at higher storage pressures for low frequency ultrasonics; at high frequency of ultrasound, the process is slowed down because of suppression of acoustic streaming. Enhancement of cavitation is the reason for better destratification at low frequency of ultrasound and high storage pressure. Increase in power amplitude of ultrasound results in enhancement of destratification at all frequencies. The ability of high frequency ultrasonics to produce more acoustic streaming effects makes them highly suitable for destratification in tall containers; however, under pressurized conditions, dual-frequency mode, which combines one low frequency with a second higher frequency, is recommended.
Keywords: Ultrasound; thermal destratification; storage pressure; acoustic cavitation; acoustic streaming; sono-mixing