On the possibility of thermodynamic equilibrium in the cavitation bubbles

Abstract

Hydrodynamic cavitation is an effective means to ensure the intensification of various processes carried out in liquid media.Analysis of the results of existing and specially designed experiments to elucidate the mechanisms of the effect of cavitation on the properties of the liquid, let V.M. Ivčenko and E.D. Malimon allocate following hydrodynamic phenomena by which may be obtained by technological effects: [1] -The formation of intense pressure fields and expansion waves -the compression arising from the pulsations of cavities or in the initial stage of coalescence; -The formation of cumulative jets accompanying asymmetrical compression of the cavity; -The occurrence of oscillations of the bubble surface in the initial stage of collapse.All these phenomena are seen as a consequence of two factors [2]:-The presence of surface tension at the interface and -The curvature of the surface.For the case of cavitation, these factors may be considered necessary, but at the same time, insufficient.We consider the mechanical equilibrium of the two identical in size and shape of the surface, but of compositionally different of bubbles (cavitation and gas) in a liquid.In both cases there is surface curvature and surface tension, but the gas bubble is stable enough, whereas cavitation bubble collapses. The differences can be explained by the intensity of the processes of mass transfer of the bubble with the surrounding fluid.Parameters of the phase transition of gas is significantly different from the parameters of the phase transition the surrounding liquid. State of aggregation of the contents of the bubble, which is determined taking into account the Laplace equation ( p = 2· r ) does not change with changes in pressure (see Fig. 1). As a result, a gas bubble can be in power and thermodynamic equilibrium with the surrounding fluid, and the intensity of a possible process of mass transfer is small and is determined by the intensity of the dissolution of gas in liquid.Parameters of the phase transition the content of the cavitation cavity and its surrounding fluid are almost identical. With increasing pressure and compression of the bubble, the surrounding liquid is in a state of thermodynamic equilibrium. Vapor pressure inside the bubble, which is able to balance the effect a Corresponding author: mg-rud@mail.ru This is an Open Access article distributed under the terms of the Creative Commons Attribution License 4.0, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.