Simulation of the effect of partial and total blockage of a sub-channel on two-phase flow through a 5 x 5 square rod bundle.

The study of the effect of blockage on two-phase flow parameters in rod bundles is of significance to the prediction of the thermal-hydraulic behavior of fuel assembly under hypothetical accident conditions. The two-phase flow computational fluid dynamics method was used to simulate the fluid flow in 5 × 5 under partial (75%) and total blockage of a sub-channel. A scenario with no blockage was considered a baseline for further analysis into subsequent cases with blockages. The effect of the blockage on the pressure drop, void fraction, subchannel average velocities, and the turbulence intensity between the sub-channels were analyzed at different hydraulic diameters before and after the blockage, and compared. The 75% partial blockage of a single sub-channel increased the average pressure drop between 1Dh and 5Dh downstream by 0.47 kPa compared to the baseline scenario. Bubbles coalesce at the vicinity of the blockage. The effect of the blockage on other flow parameters extends to 46 Dh downstream of the blockages. The effect of these different blockage conditions can provide a reference for the parameter setting of the sub-channel analysis codes. [ABSTRACT FROM AUTHOR]