Influência do diâmetro na evolução do escoamento bifásico líquido-gás em golfadas em tubulações verticais

Abstract

Slug flow can be found in both industry and nature. The two-phase water-air slug flow is primarily characterized by the intermittent passage of two alternating structures: an elongated bubble and a liquid slug. This thesis aims to characterize these structures and analyze the behavior of bubble velocity along a vertical pipe, investigating the influence of diameter on the evolution of this type of flow. To achieve this objective, an experimental setup was constructed at the Multiphase Flow Research Center (NUEM) of UTFPR, consisting of a 10-meter horizontal flow section where the flow develops and passes through a 90° bend, directing it to a 14-meter vertical section. Internal diameters of 26, 40.8, and 50 millimeters were used. Measurement and phase identification stations were installed along the test line, totaling five (5) measurement stations: four (4) stations with two-wire conductive sensors and one station with a Wire Mesh capacitive sensor. Flow images were captured using a high-speed camera. Based on the experimental data, the evolution of slug flow parameters, such as elongated bubble velocity, elongated bubble and liquid slug lengths, void fraction of the unit cell, and slug passage frequency, were characterized. An analysis of void fraction distribution along the Taylor bubble and liquid slug was conducted, identifying the points with the lowest void fraction. Along the vertical section, it was observed that the velocity of the Taylor bubble increases, as well as the length of both the bubble and the liquid slug. The frequency, on the other hand, decreases as the flow develops along the test section. As the diameter increases: a) the length of liquid slugs increases; b) the lengths of Taylor bubbles decrease, and c) the slug passage frequency decreases.