Two-phase discharge rate through a sharp-edged thin-plate orifice

Experimental and analytical studies have been made on subcooled-liquid and two-phase (steam-water) discharge through a sharp-edged thin-plate orifice. It is shown that subcooled liquid discharge can be predicted by the sing-phase orifice equation, even for nearly saturated upstream conditions. Two-phase flow data, obtained by Benjamin et al. and the authors, are compared to the predictions with the homogeneous equilibrium model (HEM) and the frozen-composition slip-flow model. The frozen-slip predicts the dependency of flow rate on upstream quality reasonably well when the slip ratio is assumed to be (ρL/ρG)n. The value of the exponent n, which gives best fit to measured flow rate, ranges between 0.02 and 0.2 tending to be smaller for higher pressure. HEM underpredicts severely the discharge rates for low upstream qualities. (author)