Evolution of the structure of a gas–liquid two-phase flow in a large vertical pipe

• Published in: Nuclear engineering and design Vol. 237; no. 15; pp. 1848 - 1861
• Main Authors: Prasser, Horst-Michael, Beyer, Matthias, Carl, Helmar, Gregor, Sabine, Lucas, Dirk, Pietruske, Heiko, Schütz, Peter, Weiss, Frank-Peter
• Format: Journal Article Conference Proceeding
• Language: English
• Published: Amsterdam Elsevier B.V 01.09.2007; Elsevier
• Subjects: Applied sciences; Controled nuclear fusion plants; Energy; Energy. Thermal use of fuels; Exact sciences and technology; Fission nuclear power plants; Fuels; Installations for energy generation and conversion: thermal and electrical energy; Nuclear fuels; Two phase flow; Turbulent flow; Vertical pipe; Gas injection; Cross section (collision); Water vapor; Physical properties; Nuclear reactor; Flow regime; Test facility; Starting; Gas liquid flow; Valve; Coalescence
• ISSN: 0029-5493; 1872-759X
• DOI: 10.1016/j.nucengdes.2007.02.018

The evolution of the structure of a gas–liquid flow in a large vertical pipe of 195 mm inner diameter was investigated at the TOPFLOW test facility in Rossendorf. Wire-mesh sensors were used to measure sequences of two-dimensional distributions of local instantaneous gas fraction within the complete pipe cross-section. The sensors own a resolution of 3 mm at a frequency of 2500 Hz. Superficial velocities were varied in a range covering flow regimes from bubbly to churn-turbulent flow. The distance between the gas injection and the sensor position was changed using a so-called variable gas injection system. It consists of six gas injection units, each equipped with three rings of injection orifices in the pipe wall (orifice diameter: 1 and 4 mm), which are fed from ring chambers. The gas flow towards these distributor chambers is individually controlled by valves. Measured bubble-size resolved radial gas fraction profiles reveal differences in the lateral migration of bubbles of different size starting from the injection at the wall. The evolution of bubble-size distributions allows to study bubble coalescence and break-up. The influence of the physical properties of the fluid was studied by comparing cold air–water experiments with steam–water tests at 65 bar.