Two-phase flow in vertical tubes and flooding in packed columns

Abstract

Systems involving gas-liquid phase concurrent vertical flows are found important in evaporators and in the simultaneous transport of oil and gas in wells. For the two-phase flow study, flow regimes and the hydrodynamics of slug were determined. Experimental measurements were carried out in a vertical tube with 1.9 cm in diameter and 300 cm in length using an air-water system. The superficial air velocities used were in the range of 0 to 14.67 cm/s, whereas the superficial velocities of water were 2.93 to 70.42 cm/s. Bubble to slug flow pattern map was generated. In addition, the relation between rise velocity of single slug and the slug length, rise velocity of continuously generated slug, void fraction and air-lift pump operation within slug were investigated. All results conformed to the Nicklin's models. Flooding, an important physical phenomenon in two-phase countercurrent packed towers, was studied experimentally by varying the type (ceramic ball and plastic rachig ring) and the heights (60 and 80 cm) of packing material in column with a diameter of 8.4 cm and 128 cm long. The rang of water mass velocities studied was 0.15 to 0.60 g/cm2.s and the air mass velocities between 0 to 11.66 g/cm2.s. The Eckert type charts of different packing materials were studied to find the scope of flooding. The results showed that ceramic balls gave lower lower scope of flooding than plastic raschig rings did and at different heights of the same packing, they gave the same transition between normal and flooding operation. For the pressure drop study, an in gas mass velocities and water mass velocities at constant air mass velocity caused an increase in pressure drop.