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Experimental Investigation of High – Frequency, High -Intensity Ultrasonics for De-Stratification of Liquids Stored in Insulated Containers
R. Vetri Murugan, R. Nagarajan and K. Ramamurthi

The effectiveness of high-frequency, high-intensity ultrasound in accelerating mixing phenomena in liquid storage tanks of varying physical dimensions and aspect ratios is experimentally investigated. The accelerated mixing of hot water and cold water in a FRP (Fiber Reinforced Plastic) cylinder was studied for different ultrasonic frequencies (58/192 KHz, 172/192 KHz, 58 KHz and 132 KHz) with 200–500 W power input. To study the kinetics of sono-mixing, the storage tank containing the warm layers of water over the cold water was placed in an ultrasonic tank filled with water. The temperature distribution of the water in the FRP tank was measured using thermocouples. The temperature data collected by the data acquisition system were transmitted to a personal computer which recorded the instantaneous reading. Ultrasonically-enhanced mixing was thus studied. Dual frequency operation, which combines one high-frequency mode with one low-frequency mode, is found to be optimal in enhancing mixing. Mixing efficiency increases with cavitation intensity and the introduction of acoustic streaming augments it further.

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