A comparison between polydispersed and monodispersed radius modeling techniques of droplets in condensing steam flow in a supersonic nozzle by Eulerian-Lagrangian method

Condensation phenomena in steam flow, can cause droplets with different sizes to form. For an exact prediction of two phase flow behavior, it is necessary to consider the effects of all droplets with different sizes on the steam. In this paper, nucleation equation in an Eulerian–Lagrangian framework has been used to analyze one–dimensional flow of wet steam in a supersonic convergent–divergent nozzle. Polydispersed and monodispersed radius methods for modeling the formed droplets are compared. In polydispersed method, all the formed droplets in the spontaneous condensation zone, are retained in the calculations, without being merged with other groups; but in monodispersed method, all groups are merged, and only one group with averaged radius is retained in the calculations. The polydispersed method has an advantage and can predict the complete droplet spectra. Results of comparing the two methods with experimental data indicates that the predicted radius in the polydispersed method, in every four investigated cases, is closer to experimental data, than that of monodispersed method.