Evaluation of Mass Accommodation Coefficients of Water over a Wide Temperature Range and Determination of Diffusion Coefficient of Water in Nitrogen

Diffusion coefficient of water in nitrogen (Dvg) is a critical thermophysical parameter. However, the widely used empirical parametrizations of Dvg are only applicable in the temperature range from 273 K to 373 K. In the supercooled range, the reported experimental values of Dvg is sparse, and Dvg varies with temperature in a way different from the empirical equations and the recently reported first-principles calculation. In this paper, Dvg values at given temperatures, including in the supercooled range, were determined using the evaporation kinetics of individual water droplets in nitrogen flow under well-controlled conditions. The KVH model capable of describing the rapid evaporation/condensation process of an individual water droplet was utilized, and the thermophysical/kinetic parameters were evaluated carefully. Through reviewing the literature values of mass accommodation coefficient (αM) for ice, ice with liquid-like layer, supercooled water, normal water, and hot water, it is observed that the Slogistic1 function presented by OriginPro® could describe the temperature dependence of αM well. Then, the radius vs. time curve of an individual water droplet was predicted from the KVH model by varying Dvg and then compared with the experimental curve recorded by the Electrodynamic Balance. The trial value of Dvg corresponding to the best agreement was treated as its experimental value. By reviewing and regression fitting of all available experimental data, an improved expression of Dvg is proposed. The accuracy is evaluated to be ± 4 % in the temperature range of 248 K to 600 K.