D2O-H2O Condensation in Supersonic Nozzles. II. Modeling

An integral steady state model of nucleation and condensation was used to examine the formation and growth of D2O droplets in a supersonic nozzle. The classical nucleation rate expression was used together with isothermal and nonisothermal droplet growth laws. For each experiment, the nucleation rate expression was multiplied by a temperature independent parameter in order to match the experimentally observed onset of condensation. In all cases, the predicted pressure traces lie above the measured ones. For one of the condensation experiments, the corresponding neutron scattering spectrum was also available. Modeling showed that once the rate expression was adjusted to match onset, the predicted scattering spectrum was a strong function of the growth law. Furthermore, the match between the measured and predicted scattering spectra was much better for the isothermal growth law than for the nonisothermal growth law.