Analysis of Temperature Field in a High-Intensity Ultrasonic Chamber

Abstract

High-intensity ultrasonic vibration in narrow resonators creates various thermal effects, which has turned it in recent years into a promising new technology in ultrasonic power determination, as well as ultrasonic diagnostic and miniaturized thermoacoustic refrigerators. As a new type of thermoacoustic engine, miniature thermoacoustic device research is still in its infancy. The thermal effects in these engines are partly studied by assuming that the mean temperature in these machines does not change. In view of the aforementioned, complete calculations related to the generation, propagation, and temperature stabilization processes of high-intensity ultrasonic waves in a duct were performed, with the intention of providing a comprehensive view of the thermal processes in linear and nonlinear ultrasonic chambers. The mean temperature distributions and the related acoustic streaming patterns were predicted to vary with the increasing driving amplitude. A weak shock wave was generated in the large-amplitude cases. The integrated effects of the hysteresis loss, acoustic streaming, and weak shock led to dramatic variations of the heat flux transferred between the fluid and the isothermal walls in different amplitude acoustic fields. The results could guide the arrangement of measurement points in the determination of ultrasonic power, and they are significant for improving the efficiency of thermoacoustic devices.