Two-phase CFD validation: TOPFLOW-PTS steady-state steam-water tests 3–16, 3–17, 3–18 and 3–19

For the Pressurized Thermal Shock (PTS) issue, the NEPTUNE_CFD code solves the Eulerian two-fluid model with specific models for liquid/gas interfaces, which are much larger than the computational cells size. The CFD validation database dedicated to PTS includes the TOPFLOW-PTS experiment, which represents condensation phenomena in a PWR cold leg, with the Emergency Core Cooling system (ECC) and a downcomer. The present study deals with NEPTUNE_CFD calculations of steady-state steam-water tests 3–16, 3–17, 3–18 and 3–19, which differ each other by the ECC liquid inlet flow rate (m˙L,ECC). So the liquid turbulence, which is the main input of the condensation models, is changed from one test to the other, firstly in the ECC region. The direct and first order effect of the ECC flow on the liquid temperature is shown with sensitive two-phase flow regime transitions, which require a careful meshing. This condition being fulfilled, satisfactory NEPTUNE_CFD results mesh-independency on refinement is shown. Present CFD is able to calculate the effect of m˙L,ECC on condensation and temperatures. CFD versions with k-ɛ and Rij-ɛ SSG turbulence modeling are compared and the improvement brought by the new version with Rij-ɛ SSG is shown.