Impact of ultrasonic exposure and external pressure in a closed volume on the temperature of the evaporated liquid

Abstract

The influence of ultrasonic exposure (UE) and external pressure on the process of heat and mass transfer during liquid evaporation is studied, which is an urgent task, since UE is widely used in various technological processes, and the parameters of UE and external pressure determine their effectiveness. Experimental studies of the effect of UE and pressure in a vacuum chamber on the temperature of the evaporated liquid at a constant ultrasonic frequency of 25 kHz and an amplitude of ultrasonic vibrations of 2 μm were carried out. The dependences of the change in the relative load on the amplitude of the oscillations of the bottom of the bath with a change in pressure in a closed volume are obtained, and coefficients are determined that refine the thermal physico-mathematical model of the wave processes in a liquid with ultrasound and a change in external pressure in a closed volume. The liquid temperature from the initial moment of time sharply increases from 27.7 ° C to 32.8 ° C, and then, when the pressure in the vacuum chamber reaches 45 kPa, it gradually decreases until an ice crust forms on the liquid surface. A comparative analysis of the results of mathematical modeling, taking into account the use of refinement coefficients and the results of experimental studies showing that the discrepancy between the temperature of the evaporated liquid, from the initial moment of time to the moment of formation of cavitation bubbles on the surface of the liquid, is 8%. The discrepancy between the temperature of the evaporated liquid from the moment of formation of cavitation bubbles to the freezing point of the liquid is up to 50%, which is explained by the error in measuring the temperature of the liquid with thermocouples during the formation of cavitation bubbles.