An Experimental study of two phase flow in inclined pipes
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AbstractA series of oil-air two phase flow experiments were conducted with a 25 m long acrylic pipe installed on an inclinable trestle at the University of Calgary flow loop. Three different pipe diameters of 25.8 mm, 51.2 mm and 76.3 mm at seven angles of 0°, ±1 °, ±5° and ±9° were studied. The fluids used were air and a light oil of 858 kg/m 3 density and 7 mPa.s viscosity at an average temperature of 23°C and pressure of 230 to 350 kPa. The data include flow pattern observations, liquid holdup, and pressure drop information over a wide range of gas and liquid flow rates. In addition, for the intermittent flow regime, bubble velocity, holdup in the liquid slug, bubble length, liquid fraction in the bubble portion, bubble/slug frequency and slug length are also reported. Such comprehensive data have not been reported previously on any two phase system. These data have been analyzed to test existing semi-theoretical models and new mechanistic models have been developed. The flow pattern transitions have been compared with the Taitel and Dukler flow pattern map. The transition from stratified to intermittent flow regime is predicted correctly by this analysis but the intermittent-annular and intermittent-dispersed bubble boundaries are not. Mechanistic models have been proposed for these transitions and the new theory predicts the transitions correctly. The pressure drop and liquid holdup were found to be flow pattern dependent. Intermittent flow was the dominant flow regime in upward flow while stratified flow dominated in downward inclined pipes. For intermittent flow the experimental results were compared with a modified Hubbard-Dukler analysis. Almost all parameters in this model were calculated from first principles and an interfacial shear term was added for the gas film. This model yields excellent results even for the transition region between the intermittent and truly annular flow designated as "proto" slug flow. A separated model has been proposed for stratified flow and homogeneous models for dispersed bubble and annular flow for predicting pressure drop and liquid holdup in inclined pipes. The results show good agreement with the experimental data.
Bibliography: p. 185-199.