Predictions of critical mass velocities in flashing water flow by means of second gradient model

The paper deals with numerical predictions of critical mass fluxes in two-phase water-steam flows. Special emphasis is laid on the predictions of critical flow rates for nonequilibrium water-steam mixtures. A new mathematical model has been proposed which takes into account the influence of interfaces on mass, momentum and energy transfer. It is a quasi-one-dimensional model for adiabatic channel flows. In order to determine critical mass flux the so-called natural choking criterion has been employed (PIF - possible-impossible flow). Such obtained numerical results have been compared with the results of two benchmark experiments on two-phase critical flows - Moby Dick and BNL. A reasonably good agreement between the predictions of the theoretical model and the experiments has been found.