Effect of channel curvature on phase distribution for air and water two-phase flow

Two-phase (air/water) measurements of the phase-distribution phenomena were made in a transparent model of a PWR hot leg by measuring pressure differential and conductivity at room temperature. These measurements were performed in a series of tests investigating two-phase-flow characterization. Test conditions were selected to cover a range of gas and liquid superficial velocities expected to occur in a prototypical reactor geometry during a small-break loss-of-coolant accident. For comparison, tests at high gas superficial velocities were also performed in which the void fraction was obtained with three differential pressure units. Results include average void fraction, local pressure profile, local velocity profile, and the local void-fraction profile. Results are found to be in generally good agreement with the drift-flux model for vertical pipes. A Weir Model was developed to relate the liquid flow rate with the level of water in the Omega-bend. To test this model, data were taken from three different test loops. Results appear to agree with the theoretical calculation as long as it is in the single liquid phase or the bubbly flow regime. This study also presents a new technique to estimate the local average void fraction and the liquid mean superficial velocity profile by using the conductivity probe in conjunction with a pitot tube