To classify gas-liquid two-phase mixtures according to their“flow patterns”helps qualitative understanding of the flow and leads us to a better prediction of two-phase flow parameters such as pressure drop, quality, and heat-transfer coefficient. Accordingly it is important to develop some technique to discriminate the two-phase flow pattern in a pipe quantitatively.
In this study we propose two kinds of techniques, which are applied to data in the range of 0.0-10.0m/s mixture velocity. In the first technique, measurement data of normalized differential pressures at four locations along the flow direction are used for flow pattern discrimination. In the second technique, the transit length of a bubble, which is measured at the center line of a tube by the use of a miniature optical probe, is chosen. The set of statistical parameters such as average, variance, and skewness factor of the measurement data is adopted as the set of key indexes, in order to establish objective and quantitative standards of flow pattern discrimination among the five dominant flow patterns namely, the bubbly flow, the hemispherical bubble flow, the slug flow, the froth flow, and the annular flow. All key indexes can be obtained by processing directly the measurement data without calculating the PDF (probability density function).
It is shown that the set of these statistical parameters is sufficient for characterizing the flow pattern and gives satisfactory results on the flow pattern discrimination in spite of the short sampling time and the simple data-processing.