Study of the evaporation kinetics of pure and binary droplets: volatility effect

This work presents a study on the evaporation of a volatile liquid droplet placed on a substrate and surrounded by air. We consider in this work the case of a pure liquid droplet (water, ethanol and butanol), and the case of a binary mixture droplet (water-ethanol and water-butanol). The aim of this work is to study the effect of the volatility of each component within a pure or binary droplet on the evaporation kinetics. The volatility of a liquid is considered as the ability of a substance to evaporate. One liquid is more volatile than another is the one with the lowest boiling temperature. We noticed that for pure liquid droplets, the volatility of the liquid considerably influences its life and cooling effect. After evaporation, the more volatile the liquid, the shorter the life of the droplet and the greater its cooling. The results of the simulation were compared and validated by the literature. Experimental results are used for validation and interpretation of the evaporation of water-butanol binary droplet. The behavior of the butanol in the mixture is different to that when it is pure. Despite its low volatility compared to water, strongly diluted in a water-based droplet, butanol evaporates in a preferential way. In fact, in the diluted mixture, the fraction of butanol evaporates first and is exhausted before that of water. The binary droplet tends to become a pure water droplet. We also show that, the same as in the case of the water-ethanol, the addition of butanol in water accelerates evaporation and decreases the droplet’s life.