Two-phase counter-current flow limitations in complex piping systems

Experiments have been performed to investigate two-phase air-water countercurrent flow limitations in two complex geometry test sections. One of the test sections was chosen to represent the complexity of CANDU feeders, at a 1:4 scale. In the second configuration, the effect of declining the horizontal parts of the test section was investigated. For the tested geometry, the results showed that the onset of flooding occurs at lower gas velocity as compared to those required to initiate flooding in vertical tubes or single 90° vertical bends. However, the critical gas velocity at the zero liquid penetration limit was found to be comparable to that of a 90° vertical bend.