Drift-flux correlation for upward gas-liquid two-phase flow in vertical rod bundle flow channel

Abstract

This paper has reviewed 17 available drift-flux correlations and collected 959 existing void fraction experimental data for air-water and steam-water two-phase flows in the vertical rod bundle flow channels. The performances of these drift-flux correlations have been evaluated with the collected experimental data. The evaluations conclude that the recently-developed drift-flux correlation of Schlegel and Hibiki gives the best predictions, and the drift-flux correlations of Clark et al. and Ye et al. can provide reasonable predictions for the collected experimental data. However, these drift-flux correlation series of Clark et al., Ye et al. and Schlegel and Hibiki are found to have the following three shortcomings. (1) Their distribution parameter correlation has ignored the flow regime and bubble behavior effects due to the different combinations of the non-dimensional superficial gas and liquid velocities at the same non-dimensional mixture volumetric flux under the high non-dimensional mixture volumetric flux conditions. (2) Their distribution parameter correlation has used the non-dimensional superficial gas and liquid velocities which cannot effectively reflect the pressure effect on the distribution parameter. (3) Their drift velocity correlation has ignored the drift velocity difference due to the flow regime transitions and has used the bubbly flow drift velocity correlation for all flow regimes, including the cap-bubbly, churn and annular flows. In view of these shortcomings, the present drift-flux correlation development adopts the segmented drift velocity correlations considering the features of bubbly, cap-bubbly, churn and annular flows in vertical rod bundle flow channel. The analysis for the experimental data of the asymptotic distribution parameter has shown that the asymptotic distribution parameter depends on the gas-phase Reynolds number with a feature that it linearly increases with gas-phase Reynolds number in the low gas-phase Reynolds number region, peaks at a critical gas-phase Reynolds number and exponentially decreases in the high gas-phase Reynolds number region under a certain liquid-phase Reynolds number flow conditions. This phenomenon is found to be caused by the formation and breakup processes of large-cap bubbles and their resultant intensive secondary flows corresponding to the flow regime transitions in the vertical rod bundle flow channel. So, a new distribution parameter correlation has been developed based on the gas- and liquid-phase Reynolds numbers reflecting the ratio of each phase inertial force to viscous force for the two-phase flows in vertical rod bundle flow channel. The newly-developed drift-flux correlation has been checked against various experimental data of air-water and steam-water two-phase flows in the rod bundle flow channel and a good agreement has been reached.