Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

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Gas/liquid flow in large risers

Omebere-Iyari, N. K.; Azzopardi, B. J.; Lucas, D.; Beyer, M.; Prasser, H.-M.


Although, most of the work reported on two-phase flows are limited to small pipe diameters, two-phase flow in large risers are increasingly being encountered in the petroleum and nuclear industries. In the present work, a wire mesh sensor was employed to obtain void fraction and bubble size distribution data and visualizations of steam/water flow in a large vertical pipe (194mm in diameter) at 46bar. For comparison purposes, measurements were made at similar phase velocities and physical properties to the data of Omebere-Iyari et al. (2007), which is for nitrogen/naphtha flow in a similar-sized riser. There exist significant differences between both sets of data. Churn-turbulent flow is observed in the present work instead of slug flow, and this differs from the intermittent and semi-annular flow patterns reported by Omebere-Iyari et al. (2007). The mean void fraction of the nitrogen/naphtha data is higher than that of the present steam/water data due to the differences in composition in the liquid phases. Furthermore, core peak distributions are observed for the present work in contrast to the flatter profiles predicted for the data of Omebere-Iyari et al. (2007) using a power law relationship.

Keywords: two phase flow; large diameter; vertical pipe; high pressure; wire-mesh sensor; void fraction