On droplet evaporation in the presence of a condensing substance: the effect of internal diffusion

Abstract

Evaporation and condensation of a continuum regime binary droplet accompanied by internal diffusion are investigated numerically. The evaluation of the mole fractions at the droplet surface is based on the model where a thin, well-stirred liquid film resulting from evaporation and condensation is allowed to mix with the droplet by diffusion in short time intervals. The effect of the internal diffusion on the evaporation rate of an ammonia droplet in the presence of condensing water vapour is examined. In particular, the evolution of the droplet temperature and the vapour pressure of ammonia just above the droplet surface is investigated. The influence of the significant surface dilution of ammonia on the evaporation rate is reduced because of the increased droplet temperature which results from the decreased evaporation rate.