MONODISPERSE DROPLET GENERATION BY SPONTANEOUS CONDENSATION OF STEAM FLOW IN NOZZLES

ABSTRACT

Spontaneous Condensation (also called homogeneous Condensation)of steam flow in one dimensional nozzle has been numerically modeled. The classical (Frenkel and Volmer) and Deich's nucleation theories were used. Unlike the classical theory, Deich's theory also accounts for the critical droplet size dependence upon the expansion rate in the nozzle. Pressure ratio, mean droplet size and droplet size distributions were obtained along the axial length for various nozzles. Comparisons with experimental data were made. The agreement between the numerical results and the experimental data was good. Both theories predicted the pressure ratio properly but the classical theory tended to underestimate the droplet sizes. Deich's theory is preferred for analyzing and designing new nozzles. The classical theory cannot be used for obtaining a correlation for surface tension ratio, thereby limiting its usage for new nozzles. Effects of Inlet conditions and nozzle expansion rates on mean droplet size and droplet size distributions were examined. The spontaneous condensation process results in relatively monodisperse droplets. The numerical model and the results are discussed in this paper.