Study of nonequilibrium flashing of water in a converging-diverging nozzle. Volume 2. Modeling

Technical Report · Mon Jun 01 04:00:00 EDT 1981

OSTI ID:5145124

Wu, B J.C.; Abuaf, N; Saha, P

A steady water loop with well controlled flow and thermodynamic conditions was designed, built, and made operational for the measurement of net vapor generation rates under nonequilibrium conditions. The test section consists of a converging-diverging nozzle with 49 pressure taps and two observation windows at the exit. Pressure distributions, photographic observations, diametrical averaged centerline void fraction distributions, detailed transverse distributions of the chordal averaged void fractions at 27 axial locations, and area averaged void fraction distributions along the nozzle were recorded under various flashing conditions. The development of voids in nonequilibrium flashing flows is shown to be dependent on three major factors of the void inception point which determines the initial and subsequent liquid superheats and must be accurately described; of the interfacial mass transfer rates, which depend on the local superheat and must be specified; and the local interfacial area density where the mass transfer occurs. The flashing onset correlation of Alamgir and Lienhard was extended to predict flashing inception in pipe and nozzle flows with subcooled inlet conditions. A void development model for bubbly flows was based on a simple concept for interfacial area density in conjunction with a conduction-controlled bubble growth law. A general model of vapor generation following flashing inception was also developed. In this model, bubbly flow, bubbly-slug flow, a transitional flow comprising the annular and annular-mist regimes and finally fully dispersed droplet flow were assumed to occur at successively higher void fraction ranges. On the basis that flashing inception occurred at the throat in nozzle flows with subcooled inlet conditions, and that the pressure undershoot can be calculated, a method of calculating the critical mass flow rates through nozzles was proposed, and it was checked with existing data.

• Research Organization: Brookhaven National Lab., Upton, NY (USA)
• DOE Contract Number: AC02-76CH00016
• OSTI ID: 5145124
• Report Number(s): NUREG/CR-1864-Vol.2; BNL-NUREG-51317-Vol.2; ON: TI85015953
• Country of Publication: United States
• Language: English

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