Studying the processes occurring in liquid films under thermal influence allows improving a variety of technological systems, since a thin layer aids in providing a high intensity of heat and mass transfer and a significant surface of phase contact with a minimum liquid consumption. Many Russian and international works wrote about theoretical and experimental studies of film flows, though paid insufficient attention to the study of the behavior of films of a binary homogeneous solution. This article studies the behavior of a thin liquid film containing a volatile component during local heating of a solid horizontal substrate. The presented calculations were performed for an aqueous solution of isopropanol. The author describes the formation of a specific surface shape, which is formed with a sufficient increase in the substrate temperature and the initial film thickness — the so-called “liquid drop”, separated from the main volume of the liquid by a thin extended layer, which is explained by the sequential occurrence of thermal and concentration-capillary flows. The results show a significant influence of the Laplace pressure jump on the character of the entire process. In addition, the cooling of the substrate leads to multidirectional flows, but in the opposite directions. The analysis of the functions of the temperature of the film free surface, the volatile component concentration in the solution, and the vapor density over the free surface at different times is carried out. The velocity field in liquid and gas during the evolution of thermocapillary and concentration-capillary flows is illustrated.
Free-surface film flow over topography: Full three-dimensional finite element solutions
