Estimation of the times for evaporation of pure water droplets and for stabilization of salt solution particles

Abstract

The evaporation or stabilization times of isolated pure water and salt solution particles were calculated with a previously published theory [Ferron, G. A. (1977) J. Aerosol Sci.8, 265] and other theories available in the literature. The calculated life times were most sensitive to the value of the water accommodation coefficient α_w. Comparing calculated life times for α_w = 0.04 and 1.0, the differences are within a factor of 2 for particles with a size of 10 μm and within a factor of 6 for particles with a size of 1 μm. The evaporation times of pure water particles were calculated for a temperature of 20°C and several relative humidities of the air, and the results were approximated by simple mathematical equations. These equations were extended for air temperatures between 0 and 50°C. The stabilization time of a salt solution particle for evaporation is well estimated by the life time of a pure water particle with the same size in air at the same temperature and relative humidity. Differences larger than a factor of two are found for particles containing a high salt concentration with a relative humidity in air near to the relative humidity of the saturated salt solution. The stabilization time for condensation of water on a dry salt particle as characterized by the time to reach 95% of the maximal increase in particle size is well estimated by the life time of a pure water particle with an initial diameter equal to the equilibrium diameter of the salt solution particle in the air.