Rigorous model of sessile droplet evaporation considering the kinetic factor.

Abstract

A new analytic model of isothermal evaporation of a sessile droplet in the form of a spherical cap is presented. This model is based on the rigorous theory of diffusion mass transfer and takes into account the intrinsic kinetics of the evaporation process. Due to its rigor, the presented model does not include the contact angle correction parameter f(θ) that is used in other models. An analysis of the presented model was conducted showing that a sessile droplet can evaporate in the diffusion-kinetic, diffusion, or kinetic regime. Each of these cases was considered separately. The case of sessile droplet evaporation in the constant contact radius mode (pinning) and the case of sessile droplet evaporation in the constant contact angle mode were also considered separately. A comparison of the calculated data obtained within the framework of the presented model with available experimental data on the evaporation kinetics of sessile droplets of ethanol and water into air was carried out. This comparison demonstrated that the presented model perfectly describes experimental data. In addition, this comparison demonstrated that to obtain correct results, a sessile droplet along with its surrounding gas must be isolated from the ambient atmosphere when an experiment to study the evaporation kinetics of the droplet is conducted.