Датчики уровня жидкости и анализа термодинамических процессов при ее замерзании на объемных акустических волнах

Abstract

A fundamental property of longitudinal bulk acoustic waves (BAW) is their inability to propagate in a gaseous medium due to strong absorption in the MHz range and, on the contrary, their ability to propagate in liquids. Based on this property, a liquid level sensor based on BAW is proposed. For these purposes, for the first time, it was used not to measure changes in the velocity and attenuation of waves, but to change the time of their propagation from the emitter to the receiver. It is shown that this acoustic parameter is ideal for such measurements, since it weakly depends on temperature, but depends on the aggregate state of the propagation medium. A technique has been developed for non-contact research of exo-, endo- and isothermal processes accompanying liquid-ice and ice-liquid phase transitions. With its help, the isothermal nature of the water-ice phase transition under normal conditions was experimentally demonstrated.