Experiment and analysis of air-water two-phase flow redistribution due to void drift between subchannels for hydrodynamic non-equilibrium flow

In order to provide the data to develop a void drift model used in a subchannel analysis, a new experimental data are obtained for air-water two-phase flows in a vertical channel called Ch. M-M, made up of two identical subchannels simplifying a BWR fuel rod bundle. The data include the flow redistribution of both phases due to the void drift and the void fraction in each subchannel under hydrodynamic non-equilibrium flow conditions. By fitting the above data with Lahey et al.'s void settling model (1993), we have determined a void diffusion coefficient in their model. It was found that the void diffusion coefficient for slug, churn and annular flows could be well correlated in terms of a turbulent Peclet number proposed in our previous study (Kawahara and Sadatomi, 2000b). Furthermore, a subchannel analysis code based on a two-fluid model developed in our previous study (Kawahara et al., 2000c) was examined against the present data. In the code, the void settling model was incorporated with usual conservation equations of mass and momentum. From the examination, it was found that the subchannel analysis code can predict well the data on the flow redistribution and the void fraction if appropriate correlations were used to evaluate the wall and the interfacial friction forces needed in the two-fluid model. (author)