Condensation of Metal Vapors During Rapid Expansion

A study has been made of the condensation of metal vapors in nozzles, using the liquid drop nucleation theory, to predict the incidence of condensation and its effect on the properties of the fluid stream. The theory, which has been verified by accurate experimental data on steam, predicts that in the absence of charged particles initially saturated mercury vapor, for example, is very reluctant to condense in a nozzle. On the other hand, the vapors of sodium, potassium, and rubidium should condense very readily. In each case the typical size and growth rate of the condensed drops is so small that significant slip between vapor and liquid phases is very unlikely to develop. The nucleation process is rapid so that equilibrium is approached quickly. In reasonably long nozzles it may be quite in order to idealize the transition between supersaturated and equilibrium states as a step change.