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 ( D vg ) is a critical thermophysical parameter. However, the widely used empirical parametrizations of D vg are only applicable in the temperature range from 273 K to 373 K. In the supercooled range, the reported experimental values of D vg is sparse, and D vg varies with temperature in a way different from the empirical equations and the recently reported first-principles calculation. In this paper, D vg 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 ( α M ) 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 α M well. Then, the radius vs. time curve of an individual water droplet was predicted from the KVH model by varying D vg and then compared with the experimental curve recorded by the Electrodynamic Balance. The trial value of D vg 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 D vg is proposed. The accuracy is evaluated to be ± 4 % in the temperature range of 248 K to 600 K.