A comparison of cluster size distribution models in isothermal single component condensation

Abstract

A review of single component condensation models is presented. The most exact model for condensation is the set of Becker-Dö ring equations. The first step toward reduced models is obtained by performing a Taylor series expansion on the discrete Becker-Dö ring equations, resulting in the Fokker-Planck equation. Further simplification of the FokkerPlanck equation leads to the stationary diffusion flux model, which is based on a steady state assumption in the region of small clusters. Discarding the small cluster size region results in the general dynamic equation, which is computationally the most attractive model. All condensation models are aimed at solving the cluster size distribution and differ in their ability to capture the physical process and their computational complexity. The assumptions needed to construct these reduced models are explained and the influences on the physical outcome are addressed. The models are applied to a nucleation pulse experiment and the computational times are compared.