Inlet effects on vertical-downward air–water two-phase flow

Shouxu Qiao, Daniel Mena, Seungjin Kim

    Research output: Contribution to journalArticlepeer-review

    27 Scopus citations


    This paper focuses on investigating the geometric effects of inlets on global and local two-phase flow parameters in vertical-downward air–water two-phase flow. Flow visualization, frictional pressure loss analysis, and local experiments are performed in a test facility constructed from 50.8 mm inner diameter acrylic pipes. Three types of inlets of interest are studied: (1) two-phase flow injector without a flow straightener (Type A), (2) two-phase flow injector with a flow straightener (Type B), and (3) injection through a horizontal-to-vertical-downward 90° vertical elbow (Type C). A detailed flow visualization study is performed to characterize flow regimes including bubbly, slug, churn-turbulent, and annular flow. Flow regime maps for each inlet are developed and compared to identify the effects of each inlet. Frictional pressure loss analysis shows that the Lockhart–Martinelli method is capable of correlating the frictional loss data acquired for Type B and Type C inlets with a coefficient value of C = 25, but additional data may be needed to model the Type A inlet. Local two-phase flow parameters measured by a four-sensor conductivity probe in four bubbly and near bubbly flow conditions are analyzed. It is observed that vertical-downward two-phase flow has a characteristic center-peaked void profile as opposed to a wall-peaked profile as seen in vertical-upward flow. Furthermore, it is shown that the Type A inlet results in the most pronounced center-peaked void fraction profile, due to the coring phenomenon. Type B and Type C inlets provide a more uniform distribution of the void fraction profile with a reduced coring effect.

    Original languageEnglish (US)
    Pages (from-to)375-388
    Number of pages14
    JournalNuclear Engineering and Design
    StatePublished - Feb 1 2017

    All Science Journal Classification (ASJC) codes

    • Nuclear and High Energy Physics
    • Nuclear Energy and Engineering
    • Materials Science(all)
    • Safety, Risk, Reliability and Quality
    • Waste Management and Disposal
    • Mechanical Engineering


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