Theoretical and Experimental Investigation of Subcooled Flashing Flow through Simulated Steam Generator Tube Cracks

Flow models and experiments were developed to predict the choking flow of subcooled flashing water through steam generator tube crack. Experiments were conducted for vessel pressures up to 7 MPa with various subcoolings through 7 sets of simulated crack geometries with channel length to diameter ratios from 1.3 to 2, and channel length of 1.3 mm. Mass flux data with respect to subcooling are presented for all seven sets of crack specimens. As the subcooling increased for each specimen the mass flux increased. In general as the mass flux increased the area of the specimens increased. Experimental data were compared with homogeneous equilibrium and non-equilibrium mechanistic models for two-phase choking flow. A comparison of the model results with experimental data shows that the homogeneous equilibrium-based models grossly underpredict choking flow rates in such geometries, while homogeneous non-equilibrium models greatly increase the accuracy of the predictions.