Evolution of hydrodynamic and statistical parameters of gas–liquid slug $ow along inclined pipes

The development of slug $ow along two 10 m long inclined pipes (2–90◦ from the horizontal) with internal diameters of 0.024 and 0:054 m was measured by three optical 4ber probes. The probes were located in a measurement module at axial distances of 0:020 m between the 4ber tips. To measure the evolution of slug $ow, the module was placed at di6erent positions along the pipe. Instantaneous elongated bubble velocities and corresponding elongated bubble and liquid slug lengths were determined by processing the optical probe signals. The evolution of the liquid slug and elongated bubble length distributions along the pipes is characterized by a gradual growth of the mean and mode values. The growth rate decreases with decreasing inclination. Mean elongated bubble lengths have a minimum at about 60◦, while mean liquid slug lengths decrease slowly with decreasing inclination angle. The coalescence rate, de4ned as the decrease in the ensemble size, becomes almost negligible at x=D¿ 60, independent of pipe diameter, $ow rates and inclination angle. The slug frequency has a maximum at about 60◦ inclination. ? 2002 Elsevier Science Ltd. All rights reserved.