An experimental investigation of the countercurrent flow limitation

A new correlation for the prediction of the Countercurrent Flow Limitation (CCFL) in a large diameter tube with a falling water lm is proposed. Dierent from previous correlations, it predicts the onset of ooding by considering the relative velocities of the working uids and the lm thickness of the liquid layer. This provides a more complete accounting of the physical forces contributing to CCFL. This work has been undertaken in order to provide a better estimate of CCFL for reactor safety codes such as MELCOR, MAAP, and SCDAP/RELAP. Experiments were conducted to determine the CCFL for a 3-inch inner diameter smooth tube with an annular liquid lm and air injection from the bottom. The size of the test section and the range of working uid ow rates were based on a scaling analysis of the surge line of a PressurizedWater Reactor pressurizer. An experimental facility was designed and constructed based on this analysis in order to collect data on the CCFL phenomenon. In order to capture some of the physical phenomena at the onset of ooding visual pictures were taken at high speed. These pictures provided a new understanding of the process of transition to ooding. The facility also produced a new set of ooding data. This can also lead to a more comprehensive mechanistic model.