Homogeneous Vapor Nucleation and Superheat Limits of Liquid Mixtures

Abstract

Two features distinguish vapor nucleation in multicomponent liquids from the single component case. Both result from the unequal volatilities of the species. One is that the vapor phase may contain several components; the other is that nucleus formation alters the composition of the nearby liquid. These two features are incorporated into the classical theory of homogeneous nucleation to yield a general theory applicable to multicomponent liquids. The theory is applied to binary hydrocarbon mixtures by using an equation of state extrapolated into the metastable region. Superheat limits thus calculated are compared with published experimental results.

High Pressure Homogeneous Nucleation of Bubbles within Superheated Binary Liquid Mixtures

“…6-8. This fact was previously observed at atmospheric pressure [11,12,18]. However, this nearly linear variation of limit of superheat with mole fraction is by no means a universal result.…”

“…4 and 5. In these calculations, the possibility that the composition of the liquid in the vicinity of the nucleus is different from that in the bulk because of preferential vaporization and local depletion of the volatile species, as discussed by Pinnes and Mueller [18], was neglected. Reid [34] argues that such effects are negligible because the number of molecules within the vapor nucleus is small compared to the enormous number of molecules in the liquid.…”

“…The physical properties of mixtures often cannot be predicted as accurately as the properties of pure liquids. The accuracy of such predictions has a very strong effect on the ability to obtain a meaningful estimate of the homogeneous nucleation temperature [11,12,18].…”