Evaporation of aqueous solutions of LiBr and LiCl salts

摘要

An experimental study of evaporation of a drop and a thin layer of salt solutions located on a hot horizontal wall has been performed. In technical problems, it is necessary to simulate the evaporation of a small droplet, a pool and a film simultaneously. Drops falling on the wall merge and form a thin film. The density of the steam flow for a drop is assumed to be much higher than for a layer with identical conditions of evaporation, since for a drop the Marangoni number and the free convection velocity in the liquid are larger, as well as due to the concentration field distribution in the vicinity of the drop and the film. However, the obtained results have shown the opposite effect. The evaporation rates for a drop and thin layer appear to differ significantly due to different dynamic background. It reflects the ratio of the thickness of the wall boundary velocity profile for the gas phase to the thickness of the boundary concentration profile for the gas mixture (water vapor-air). Curves of the salt concentration changes over time have been built. It is also shown that the crystallization rate is controlled by the rate of the liquid evaporation until the beginning of crystallization. For correct simulation of evaporation, it is necessary to take into account the thermal and dynamic background.