Numerical investigation of the effect of the shape of the nozzle on the flash boiling phenomenon

In this paper analysis of influence of the nozzle shape on the flash boiling phenomena is presented. The mixture model was applied to account for two-phase flow through the nozzle. The ZwartGerber-B lamri model was used to describe the dynamics of the water-vapor phase change process, with the relationship linking the saturation pressure and temperature of the fluid. The effect of the shape of the nozzle on the mass flow rate of the two-phase mixture was numerically investigated by considering thestepwise and conical geometry of its divergent part. At first analysis of the influence of grid size as well as the ways of turbulence and near wall region modelling on the mass flow rate of two-phase mixture were studied for the diameter of nozzle neck of 0.42 mm. Predictions were found independent onthese factors. Then simulations were carried out for three nozzle neck diameters (i.e., 0.62, 0.72 and 0.82 mm) and for several pressures (i.e., from 5 to 7 bar) and undercoolings (i.e., from 1 to 50 K)of water at the inlet. The shape of divergent part of the nozzle was found to not have effect on the mass flow rate of flashing water flowing through nozzle