Temperature Dependence of Evaporation Coefficient for Water Measured in Droplets in Nitrogen under Atmospheric Pressure

Abstract

The evaporation and the thermal accommodation,coefficients for water in nitrogen were investigated by means of the analysis of evapo- ration of pure water droplet as a function of temperature. The droplet was levitated in an electrodynamic trap placed in a climatic chamber. The levitation time was in the range of seconds, which corresponds to the characteristic timescales of cloud droplet growth. Droplet ra- dius evolution and evaporation dynamics were studied as a function of temperature, by analyzing the angle-resolved light scattering Mie in- terference patterns. A model of droplet evolution, accounting for the kinetic effects near the droplet surface was applied. The evaporation coefficient for the temperature range from 273.6 K to 298.3 K was found to be between 0.054 and 0.12 with a minimum,of 0.036 seemingly coinciding with water maximum,density at 277.1 K. The average value of thermal accommodation,coefficient over the temper- ature range from 277 K to 289 K was found to be 0.7,. Keywords: water droplet, evaporation coefficient, electrodynamic trap, Mie theory 1