Droplet and bubble nucleation modeled by density gradient theory – cubic equation of state versus saft model

¹ Institute of Thermomechanics AS CR, v. v. i., Dolejškova 1402/5, 182 00 Prague 8, Czech Republic
vins.vaclav@seznam.cz, hruby@it.cas.cz, barbora.plankova@gmail.com
² Czech Technical University in Prague, Faculty of Nuclear Sciences and Physical Engineering, Břehová 7, 115 19 Prague 1, Czech Republic

Abstract

The study presents some preliminary results of the density gradient theory (GT) combined with two different equations of state (EoS): the classical cubic equation by van der Waals and a recent approach based on the statistical associating fluid theory (SAFT), namely its perturbed-chain (PC) modification. The results showed that the cubic EoS predicted for a given surface tension the density profile with a noticeable defect. Bulk densities predicted by the cubic EoS differed as much as by 100 % from the reference data. On the other hand, the PC-SAFT EoS provided accurate results for density profile and both bulk densities in the large range of temperatures. It has been shown that PC-SAFT is a promising tool for accurate modeling of nucleation using the GT. Besides the basic case of a planar phase interface, the spherical interface was analyzed to model a critical cluster occurring either for nucleation of droplets (condensation) or bubbles (boiling, cavitation). However, the general solution for the spherical interface will require some more attention due to its numerical difficulty.