Two-phase critical flow of saturated and subcooled liquids through valves

Two phase critical flow experiments were conducted to determine the effect of nonideal geometries on critical flow rate. A globe valve and a relief valve were tested, along with a 15 deg converging-diverging nozzle as a reference. Freon-11 was used as the working fluid; test conditions ranged from 5 to 60 C subcooling at inlet pressures of 550-2220 kPa. The data show that the two phase discharge coefficient is about 15% lower than the single phase discharge coefficient; in addition, critical flow rate can be predicted to within 20% by using the single phase discharge coefficient in simple analytical models.