Experimental study of two-phase flow in rod bundle

This research focused on the study of the air-water two-phase flow in a scaled nuclear reactor rod bundle geometry. Global flow regimes were obtained for the rod bundle geometry. A grid loss model was established and evaluated using pressure drop database. Drift flux model evaluation was also conducted in this study using the 1-D void fraction database. Local two-phase flow parameters were measured at different axial locations in order to understand the detailed flow structure in a rod bundle geometry. Air-water two-phase flow experiments were performed in an 8X8 rod bundle test section. Area-averaged void fraction was measured by wire mesh type impedance meters. Different drift flux model were evaluated using this measured void fraction database, while the cumulative probability distribution functions of the signals from the impedance meter were used to identify flow regimes with a self organizing neural network. Pressure drop was measured by a differential pressure measurement cell. The pressure drop database was further analyzed and utilized to evaluate the grid loss model. Local parameters were measured at different gas and liquid velocities. The analysis focused on both radial and axial development of the two-phase flow structure. Investigation on the effect of spacer grid is also conducted