Temperature dependence of evaporation coefficient of water in air and nitrogen under atmospheric pressure; study in water droplets

The evaporation coefficients of water in air and nitrogen were found as a function of temperature, by studying the evaporation of pure water droplet. The droplet was levitated in an electrodynamic trap placed in a climatic chamber maintaining atmospheric pressure. Droplet radius evolution and evaporation dynamics were studied with high precision by analyzing the angle-resolved light scattering Mie interference patterns. A model of quasi-stationary droplet evolution, accounting for the kinetic effects near the droplet surface was applied. In particular, the effect of thermal effusion (a short range analogue of thermal diffusion) was discussed and accounted for. The evaporation coefficient α in air and in nitrogen were found equal. α was found to decrease from ∼ 0.18 to ∼ 0.13 for the temperature range from 273.1 K to 293.1 K and follow the trend given by Arrhenius formula. The agreement with condensation coefficient values obtained with essentially different method by Li et al.1 was found excellent. The comparison of experimental conditions used in both methods revealed no dependence of evaporation/condensation coefficient upon