Formation of Monodisperse and Narrow Disperse Ensembles of Droplets of Aqueous Organic Solutions in the Vapor of Volatil
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Journal of Engineering Physics and Thermophysics, Vol. 93, No. 5, September, 2020
FORMATION OF MONODISPERSE AND NARROW DISPERSE ENSEMBLES OF DROPLETS OF AQUEOUS ORGANIC SOLUTIONS IN THE VAPOR OF VOLATILE COMPONENTS V. B. Fedoseeva and E. N. Fedoseevab
UDC 622.276
The equilibrium state of solution droplets formed in the vapor of volatile components has been considered. The criterion of equilibrium of the solution droplets and the vapor of volatile organic compounds has been given, on whose basis the droplet size was estimated quantitatively as a function of the partial pressure of the components. In accordance with a thermodynamic description, the droplet size was unambiguously determined by the composition of a gas medium. The equilibrium state (radius and concentration) of droplets of ideal and real binary solutions has been compared at the same composition of the gas medium. It has been shown that the droplet size of the real solutions with a positive deviation from ideality exceeds the droplet size of the ideal solution, and the droplet size of the real solutions with a negative deviation from ideality is smaller than that of the ideal solution. The described regularities have been illustrated by microscopic photographs demonstrating the forming of an ensemble of secondary droplets. Keywords: disperse system, liquid–vapor equilibrium, droplets, ideal and real solutions, dimensional effect, condensation, evaporation. Introduction. Investigations into the formation and stability of fogs, aerosols, and emulsions have been relevant for longer than half a century [1–4]. From the viewpoint of chemical thermodynamics and colloidal chemistry, the equilibrium and stability criteria of heterogeneous systems are of common nature. The interest in this problem has not waned yet, and it is due to the development of spray technologies of obtaining submicron and nanodisperse materials and coatings [6, 7], and also to the necessity of raising the efficiency of combustion of fuels [8–10] and solving other problems [11]. Our interest is in chemical and phase transformations in disperse systems, in particular, in the formation of secondary aerosols [12, 13] and in the influence of the composition of a gas medium on the size distribution of solution droplets and the evolution of this distribution with time [14, 15]. A thermodynamic description and the observation of phase transformations in droplets [16–18] enabled us to predict certain important features of the behavior of solution of nonvolatile components in a small volume [16] and unusual dynamic effects in them [19, 20]. In the literature, there is no description of such regularities of the behavior of organic compounds of high volatility. Behavioral features of disperse systems of complex chemical composition are of interest for a wide range of practical applications. These features are largely determined by dimensional effects, which makes it relevant to investigate methods of forming systems that fall within assigned dimensional intervals. In the present work, we give the
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