Enhancement of heat transfer in forced convection by using dual low-high frequency ultrasound.

Combined sonication with dual-frequency ultrasound has been investigated to enhance heat transfer in forced convection. The test section used for this study consists of a channel with, on one hand, heating blocks normal to the water flow, equipped with thermocouples, and, on the other hand, two ultrasonic emitters. One is facing the heating blocks, thus the ultrasonic field is perpendicular, and the second ultrasonic field is collinear to the water flow.

Heat transfer enhancement using 2MHz ultrasound.

The present work focuses on possible heat transfer enhancement from a heating plate towards tap water in forced convection by means of 2MHz ultrasound. The thermal approach allows to observe the increase of local convective heat transfer coefficients in the presence of ultrasound and to deduce a correlation between ultrasound power and Nusselt number. Heat transfer coefficient under ultrasound remains constant while heat transfer coefficient under silent conditions increases with Reynolds number from 900 up to 5000.

Experimental characterisation of the thermal behaviour of different materials submitted to ultrasound in an ultrasonic fountain.

The purpose of this study was to characterize the thermal behaviour of different materials subjected to an ultrasonic fountain created by an ultrasonic piezoelectric transducer. Tests were conducted with an infrared camera to determine the surface temperature of the material samples. The main conclusion is that the plastics when subjected to the ultrasonic fountain tend to heat up strongly and can reach temperatures up to 200 °C in few seconds.