Measurements using X-ray attenuation vertical distribution of the void fraction for different flow regimes in a horizontal pipe

作者：Rossi L^*; De Fayard R; Kassab S

来源：Nuclear Engineering and Design, 2018, 336: 129-140.

DOI：10.1016/j.nucengdes.2017.07.037

• Flow regime
• X-ray measurements
• Void fraction
• Horizontal pipe

METERO is an experimental facility built by the French Atomic Energy Commission (CEA) aimed at studying adiabatic air-water flows in horizontal pipes. The physical insight and the experimental data provided by METERO experiments support the validation of MCFD (NEPTUNE CFD) and System (CATHARE-3) codes as a part of the NEPTUNE project developed jointly by EDF, CEA, AREVA NP and IRSN. Bottin et al. (2014) have proposed a flow map of the different regimes encountered in the METERO experiments, i.e. stratified flows, slug flows, plug flows, stratified dispersed bubbly flows and dispersed bubbly flows. Following this work, we investigate the vertical distribution of the void fraction integrated horizontally using X-ray attenuation measurements.
The use of the X-ray attenuation method presents the advantage of providing integrative measurements along the X-ray path. To obtain the vertical distribution of the void fraction integrated in the horizontal direction, the X-ray apparatus is rotated to ensure a spatial resolution of about 1 mm. For METERO's pipe of 100 mm diameter, this provides a fine discretisation of the void fraction distribution with a reasonable amount of realisations, i.e. 7 angles.
After a description of the experiments and the measurements' method, different flow regimes and their transitions (e.g. slug, plug, and bubble flow regimes) are explored by varying the water and air superficial velocities within the ranges 0.71 m/s-5.31 m/s (Reynolds number of the liquid phase varying between 71,000 and 530000) and 0.023 m/s-0.68 m/s respectively. The evolution of the vertical distribution of the void fraction in horizontal pipes is discussed. Moreover, statistics such as the ratio of the air and water phase velocities are derived from the measurements. It is shown that due to the accumulation of bubbles in the upper part of the flow (where the flow is more going slowly than in the bottom part) the air phase velocity is generally smaller than the water phase velocity for bubble and plug flows. On the contrary, the air phase velocity is generally higher than the water phase velocity for slug flows with a ratio varying like five thirds of the supplied void fraction.

• 出版日期2018-9
• 单位中国地震局