Characteristics of Interfacial Profiles in Upward and Downward Gas-Liquid Two-Phase Plug Flow

Gas-liquid interfacial porfiles in plug flow for both upward and downward flows were obtained using semi-supermultiple-point-electrode probes, comprising 67 sensing tips arranged on a tube diameter. Typical interfacial profiles are demonstrated for both flows. Close inspection reveals that four zones exist in a pair of gas and liquid slugs for the upward plug flow region and the high slip velocity region in downward plug flow. Lengths of the swelling liquid front zone and the wake zone were determined. The length of the wake zone strongly depends on the relative velocity between the liquid film around gas slug and the liquid phase in liquid slug. Characteristic distributions of bubbles within liquid slugs were found, i. e., three types of radial distributions of void fraction, namely saddle-shaped, trapezoidal and bullet-shaped distribution, exist for upward flow, while the two types except the saddle-shaped distribution exist for downward flow.