LOCAL INVESTIGATION OF SOME ULTRASONIC DEVICES BY MEANS OF A THERMAL SENSOR

The use of ultrasound is now considered, among other methods, to be a way of activation of kinetics (chemical reaction, mass transfer...) and of yield improvement in chemical engineering processes. A large variety of ultrasonic devices is presently available at the laboratory scale. Consequently, there is a need to develop experimental tools able to establish some confident rules of comparison between the various apparatuses, In the present work, the local ultrasonic intensity, emitted in the medium, is detected in the following different reactors (all exhibiting stationary ultrasonic waves): ultrasonic cleaner, horn, hexagonal tank, sonitube. The investigation relies upon the heat absorption of silicone, embedding a thermocouple. The temperature difference between the medium and the absorbing material is considered as a measurement of the local ultrasonic intensity. Consequently, nowadays it is possible to establish a cartography of the ultrasound propagation in any type of ultrasonic reactor. The sonitube presents nearly uniform ultrasound distribution. It is expected that the efficiency of the ultrasound activation will be higher in this case. A model reaction has been performed and the yield has been considerably improved due both to the ultrasound and to the sonitube.