The evaporationmdash;condensation coefficient for very small droplets is derived in the form agr;(a) =dgr;middot;phgr;(a), where dgr; is the freehyphen;angle ratio and phgr;(a) is the size coefficient which is expressed in terms of the droplet radiusa,the absolute temperature, and other characteristic variables of the liquid phase and the gasmdash;liquid interface. With the inclusion of agr;(a) into the rate equations of Fuchs and of Monchick and Reiss, the rate of evaporation per unit area increases with decreasing droplet radius, reaches a maximum at droplet radii ranging between 1 and 0.01 mgr;, then decreases to zero as the radius approaches zero. Numerical results were obtained for H2O, He, and Hg at their respective freezing and boiling points.
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