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Suitability of Drift-Flux Models, Void-Fraction Evolution, and 3-D Flow Pattern Visualization During Stationary and Transient Flashing Flow in a Vertical Pipe

Annalisa Manera, Horst-Michael Prasser, Tim H. J. J. van der Hagen

Nuclear Technology / Volume 152 / Number 1 / October 2005 / Pages 38-53

Technical Paper / Nuclear Reactor Thermal Hydraulics /

An assessment of void-fraction correlations and drift-flux models applied to stationary and transient flashing flows in a vertical pipe has been performed. Experiments have been carried out on a steam/water loop that can be operated both in forced- and natural-circulation conditions to provide data for the assessment. The GE-Ramp and Dix models are found to give very good predictions both for forced- and natural-circulation flow conditions, in the whole range of measured void fractions.

Advanced instrumentation, namely, wire-mesh sensors, has been used to obtain a detailed picture of the void-fraction development in the system. On the basis of experimental data, a three-dimensional visualization of the transient flow pattern during flashing was achieved. A transition of the flow pattern between bubbly and slug/churn regimes was found.

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