Modeling of H2O/D2O Condensation in Supersonic Nozzles

We have developed a steady state 1-D model to examine the formation and growth of H2O/D2O droplets in a supersonic nozzle. The particle formation rate is predicted using Hale's scaled nucleation model. Droplet growth is modeled with five different growth laws. Both isothermal and nonisothermal growth laws are considered. We compared the predicted droplet sizes and number densities, to the values determined by in situ small angle x-ray scattering experiments (SAXS) conducted under similar conditions. Contrary to our expectations, the isothermal calculations are closer to the experimental results than anticipated. Nonisothermal droplet growth does not quench nucleation rapidly enough and almost always overpredicts the number density and, therefore, underpredicts the droplet sizes.