Experimental investigation of a vertically downward two-phase air-water slug flow

The present experimental work investigates the vertical downward two-phase slug flow in a transparent vertical pipe of 34 mm internal diameter. The gas and liquid superficial velocities are in the range of 0–3.27 m/s and 0.015–1.4 m/s respectively. The cross-sectional averaged void fraction has been measured at seven positions along the test section by the intermediary of the conductance probe technique. The results of the development of the void fraction time-series and Probability Density Function along the tube are presented. A good accordance was found between the experimental data and the line transitions of the flow pattern map proposed by (Usui, 1989). We also present results of the structure velocity of the slug flow, where the distribution parameter is found to be lower than unity. A new correlation for the prediction of slug frequencies is also proposed. It agrees well with the data collected in this study with ±10% error.