IMPLEMENTATION AND ASSESSMENT OF THE DELAYED EQUILIBRIUM MODEL FOR COMPUTING FLASHING CHOKED FLOWS IN A MULTI-FIELD CFD CODE

摘要

In the context of a Loss of Coolant Accident (LOCA), it is important to be able to accurately predict the water/vapor flow rate through a breach in the primary circuit. This paper deals with the CFD-implementation of the Delayed Equilibrium Model (DEM), which physically tackles thermodynamic non-equilibrium conditions prevailing in the flashing flow process near the breach section. This approach is originally a ID three-phase model for choked or critical flow rate in steady state or quasi-steady state conditions. The DEM has been recently assessed against six different sets of experimental data. The chosen CFD platform, NEPTUNE CFD developed by EDF-CEA with the support of AREVA-NP and IRSN (France), solves conservation equations for an n-field problem. The proposed implementation is based on the balance equations written for three fields: the saturated vapor phase, the saturated liquid phase and the metastable liquid phase. The vaporization index correlation is properly used to implement the interfacial mass and heat transfer between the three fields. The NEPTUNECFD code is then used to simulate the Super-Mobydick experiments performed at CEA. The results are compared with the original DEM developed in-house.