SOME CHARACTERISTICS OF AIR-WATER 2-PHASE FLOW IN SMALL-DIAMETER VERTICAL TUBES

Flow regime, void fraction, rise velocity of slug bubbles and friction al pressure loss were measured for air-water flows in capillary tubes with inner diameters in the range from 1 to 4 mm. Although some flow r egimes peculiar to capillary tubes were observed in addition to common ly observed ones, overall trends of the boundaries between flow regime s were predicted well by Mishima-Ishii's model. The void fraction was correlated well by the drift flux model with a new equation for the di stribution parameter as a function of inner diameter. The rise velocit y of the slug bubbles was also correlated well by the drift flux equat ion. The frictional pressure loss was reproduced well by Chisholm's eq uation with a new equation for Chisholm's parameter C as a function of inner diameter. Copyright (C) 1996 Elsevier Science Ltd.