Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

1 Publication
Investigations on upward, downward and counter-current two-phase pipe flows using ultrafast electron beam X-ray computer tomography
Lucas, D.; Banowski, M.; Beyer, M.;
The ultra-fast electron beam X-ray computed tomography was developed during last years at HZDR and turned out to be a suitable measuring technique to get detailed information on the structure of gas-liquid interfaces. Air-water as well as steam-water experiments were done at a vertical pipe with an inner diameter of 54 mm and a test section length of about 4 m. They include co-current upward and downward flows under a wide variety of flow conditions and also some measurements for counter-current flows. In the latter case the bubble rise velocity was larger than the downward liquid velocity leading to an upward flow of bubbles and downward flow of water. Beside the tomographic reconstruction further data processing is required to obtain reliable quantitative data. A new algorithm for binarisation of the reconstructed data was developed.
The measurements were done with high frequency (between 1000 and 5000 frames per second depending on the flow conditions). In the result the instantaneous gas-liquid distributions in two horizontal planes with a distance of about 10 mm are obtained. Basing on that quantitative data like gas volume fraction distributions, average radial gas velocity profiles (basing on a cross-correlation between the two planes), bubbles size distributions and radial gas volume fraction profiles in dependence on the bubble size are obtained.
Since (in contrast to previously presented wire-mesh sensor measurements) the flow is not influenced by the measurement a bubble registered in the upstream plane can be assigned to the corresponding bubble in the downstream plane. This allows the determination of the velocity vector for each bubble. Special attention is paid to the dependency of lateral bubble velocities in dependence on the bubble sizes and the local flow conditions. Different effects are observed in upward and downward flows and will be discussed in detail.
Keywords: multiphase flow, tomography. experiment
  • Lecture (Conference)
    7th European-Japanese Two-Phase Flow Group Meeting, 11.-15.10.2015, Zermatt, Switzerland

Publ.-Id: 22869 - Permalink