Chapter 7 - Binary homogeneous nucleation in selected aqueous vapor mixtures

Abstract

Phase transitions are a fascinating feature of the physics of fluids. The water–steam phase transition plays an essential role in the power industry. The common properties of phase transition kinetics are intensively studied in chemistry and physics, and it is applied in several fields, such as metallurgy, biology, medicine, and in chemical engineering. The four stages in phase transition are: the supersaturated state, the origination of the new phase (nucleation), the growth of nuclei to form larger particles, and the relaxation processes such as coagulation and agglomeration. This chapter deals with the second and third stage: nucleation and droplet growth. Nucleation may be understood to be an initial stage of the complex, first-order phase transition leading to the formation of droplets of a new liquid phase, within the meta-stable gaseous phase. Within the framework of the kinetic approach, the evolution of nucleation is described by the nucleation equation, connecting thermodynamic and kinetic features of the process. The underlying idea of atom's clustering during nucleation is based on the Szilard assumption that the dominant role in this process is the attachment (detachment) of single particles to (from) the cluster surface. The nucleation equation may be solved either numerically or analytically. The principles of the most frequently used experimental techniques can be summarized as: thermal diffusion, cloud chamber, expansion chamber, nucleation pulse technique, nozzle flow, and condensation wave technique.