Experimental study of heat transfer performance in rectangular microchannels enhanced by ultrasound

Ultrasound is recognized as an effective technology to enhance heat transfer, which is widely used in industrial fields such as microelectronics and heat storage. However, the heat transfer characteristics in rectangular microchannels assisted with ultrasound has little revealed in present research. In this work, the external ultrasonic was added in a rectangular microchannel to reveal the influence of ultrasound on the heat transfer characteristics of micro-channels. Hence, the comparative experiments were completed to explore the heat transfer performance with and without ultrasonic. Moreover, a large number of experiments were carried out within rectangular microchannels by varying the velocity of the working fluid and the heat flux at the bottom of the microchannels. The results indicate that the heat transfer performance of rectangular microchannels can be enhanced by ultrasound. But the enhanced heat transfer effect could be limited with the increase of the flow velocity and heat flux in microchannel correspondingly. For rectangular microchannels with adding ultrasound, the lower the flow rate and heat flow density are, the better the enhancement effect will be. During the measurement, when the fluid flow velocity is 0.2 m/s and the heat flux is 408.2 kW/m2, the heat transfer performance of the ultrasound-enhanced microchannel can be improved by a maximum of 12.9 %. Additionally, the tests indicate that the pressure drop mainly comes from the viscous loss along rectangular channel, yet the ultrasound has no negative impact on pressure drop in microchannel. This work could be beneficial to the further application of ultrasonic enhancement technology.