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Measurement of the Local Properties of Multiphase Flows

Panagiotopoulos, Nickolaos (2009) Measurement of the Local Properties of Multiphase Flows. Doctoral thesis, University of Huddersfield.

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    Abstract

    Flows of mixed fluids in pipes are frequently encountered in several areas of
    engineering, such as chemical, petroleum and nuclear. Two key parameters
    characterising such flows are the local volume fraction distribution and the axial
    velocity distribution of the dispersed phase. In order to achieve a further
    understanding of the flow properties, vector velocities are important too. A common
    intrusive method that is used for acquiring these parameters is the local conductivity
    probe. The reason is that conductivity probes are more accurate than other measuring
    techniques, such as ERT (Electrical Resistance Tomography) systems, and are
    therefore used for the calibration and validation of ERT systems. Also the
    measurements from conductivity probes show a more representative distribution of
    volume fraction and velocity of the dispersed phase than other non intrusive methods.
    They are also useful for validating data produced by CFD (Computed Fluid
    Dynamics) simulations.
    In this thesis, research has been done on designing probes, and improving the
    related signal processing algorithms, and several experiments have been run in
    multiphase loops for measuring the local volume fraction and velocity of the
    dispersed phase in vertical and inclined pipes and in swirling flows. All these attempts
    have recognised an extra problem that is not negligible when using local conductance
    probes. This problem is the interaction between the probe and the bubble. It is known
    that local probes alter the true value of the bubble’s vector velocity due to the fact that
    bubbles are slowed down by the probe.
    A number of experiments were performed and a comparison between ERT and
    local conductivity probes was made. Both techniques gave velocity distributions of
    the dispersed phase which do not agree, showing that ERT is unable to accurately
    measure the gas velocity and volume fraction profiles.
    Furthermore the current thesis presents results from dual sensor and four
    sensor local conductivity probes in steady vertical and inclined air-water and oil-water
    flows and in steady swirling flows, and a proposed new design for fabricating a rotary
    index dual sensor probe with a new algorithm for the signal processing scheme is
    given. This new type of conductivity probe has a relatively small frontal area that
    reduces the bubble-probe interaction hence the probe’s effect on the dispersed phase
    is less that of other types of probe.

    Item Type: Thesis (Doctoral)
    Subjects: T Technology > T Technology (General)
    T Technology > TJ Mechanical engineering and machinery
    Schools: School of Computing and Engineering
    Depositing User: Carol Doyle
    Date Deposited: 10 Nov 2009 11:06
    Last Modified: 28 Jul 2010 19:49
    URI: http://eprints.hud.ac.uk/id/eprint/6136

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