Movement of water vapor in sand column and mechanisum of evaporation

Abstract

This paper presents an experimental investigation on the movement of water vapor in a sand column, which is comprised of dry, capillary and saturated zones, and the relationship between the vapor pressure profile and evaporation velocity. The vapor pressure is obtained from the simultaneo us measurements of temperature and relative humidity. It became clear that the evaporation actively occurred near the capillary fringe and most of the evaporated water vapor moved toward the atmosphere and the remaining water vapor moved downward and then condensed. The experimental results for the vapor pressure profiles well agreed with the theoretical results based on the one way diffusion theory. A comparison between the theoretical and experimental results demonstrated the importance of the effect of the vapor pressure gradient across the dry zone on the evaporation velocity.