On the theory of capillary evaporation in porous bodies

Capillary evaporation is a relatively new phenomenon that is analogous to capillary condensation, which takes place upon formation of pores in a solid body surrounded by a nonwetting liquid. The first theories of capillary evaporation dealt with very simple slit and cylindrical pores. A theory of wedgelike pores is formulated in the present work. In contrast to capillary condensation, capillary evaporation leads to the formation of a gas-liquid interface with a curvature radius that is greater than nanosize and nonwetting provides the position of the meniscus in a significantly wide part of the pore. This makes it possible to use concepts of surface tension and contact angle. Exact position of the meniscus inside the wedgelike pore is found as a function of liquid-vapor interface radius, contact angle, and dihedral angle of the pore itself. The influence of the temperature is analyzed, and it is shown that the meniscus shifts to the mouth of the pore with its increase.