Experimental Study on Heat Transfer Enhancement of Water-water Shell-and-Tube Heat Exchanger Assisted by Power Ultrasonic

High-intensity ultrasound can induce cavitation bubbles and acoustic streaming in liquid, which makes it possible for power ultrasonic to be applied to the improvement of heat transfer process. In the present work, the experimental study was made on the heat transfer enhancement of water-water heat exchanger in shell-and-tube type assisted by power ultrasonic. The design of the experimental system is presented in detail, and the experimental procedures is expounded as well to make the study process more clearly. The acoustic frequency of ultrasound transducer employed is about 21 kHz, and three power levels (40W, 60W and 100W) are used for this study. The impact of water flow rate and inlet water temperature in the tube as well as the ultrasonic power on the enhancement were investigated. It was found that the water flow rate and ultrasonic power levels would produce great influence on the enhancement by power ultrasound which decreased with the increasing water velocity in the tube and the decreasing acoustic power. However, the experimental results were not as favorable as expected. Some problems are addressed for the future study.