Countercurrent flow limitation in a PWR hot leg

In order to evaluate countercurrent flow limitation (CCFL) characteristics in a PWR hot leg under reflux condensation, numerical simulations have been done for pressures of 0.1 MPa < P < 8 MPa using a VOF (volume of fluid) method implemented in the computational fluid dynamics software, FLUENT6.3.26. In this paper, first Wallis-type CCFL correlations for air-water and steam-water conditions were derived using the previously measured data and calculated results. The slope m was 0.70 and CCFL constants were C = 0.63 ± 0.02 and C = 0.655 ± 0.025 for air-water and steam-water conditions, respectively. Then, numerical simulations were additionally done by using the VOF method to evaluate the effect of fluid properties at a pressure of 16 MPa, and it was shown that the Wallis-type CCFL correlation for steam-water conditions could be used in the pressure range of 0.1 MPa < P <16 MPa. Finally, effects of fluid properties on CCFL characteristics were discussed.