Development of the simplified boiling model applied for the large scale simulation by the detailed two-phase flow analysis based on the surface tracking

Abstract

Japan Atomic Energy Agency (JAEA) is developing the evaluation method for a two-phase flow in the reactor core by the simulation code based on the Volume Of Fluid (VOF) method. However, it is impossible to simulate boiling on the heating surface in the large-scale domain like fuel assemblies by this type of simulation method since the simulation of boiling based on the VOF method needs the fine meshes which sufficiently resolve the initiation of boiling. Therefore, JAEA started to develop a simplified boiling model applied for the two-phase flow in the fuel assemblies. In this study, the simulation of the convection boiling on a vertical heating surface is simulated using the developed simplified boiling model. The comparison between the simulation results and experimental results showed the excellent reproducibility of the heat flux and velocity dependency on the passage time length of the bubble.