Numerical investigation of convection heat transfer characteristics in sloshing corium pools

Abstract

The convection flow and heat transfer actuated by internal decay heat and the sloshing of vessels are the primary problems in the study of thermal behaviors in volumetrically heated reactor corium pools under ocean conditions. The wall-modeled large eddy simulation (WMLES) method, volume of fluid model, and phase-change model combined with dynamic mesh technology, were used to develop a three-dimensional flow and heat transfer process simulation model of the sloshing corium pool. In addition, the heat conduction behavior in the crust and vessel wall, as well as the pressure-vessel-wall integrity evaluation was considered. The predicted internal heat transfer characteristics (the temperature distribution, the wall heat flux, and the shell thickness) in the corium pool and the evolution feature of the free surface height near the wall were in good agreement with the LIVE-L4 test results and sloshing experimental data, respectively. Furthermore, the coupled heat transfer phenomenon of the melt and vessel was simulated. The simulation results indicated that the time required to reach stable heat transfer was shortened, the structure of thermal stratification was transformed, and the heat flux along the inner surface of the vessel wall of the shell was improved at the resonance state. The comparisons of local Nusselt (Nu) number at the near-wall between static and sloshing corium pool conditions showed that heat transfer characteristics were significantly influenced by sloshing (T = 2.5 s, A = 0.07 rad) motion, and the Nu number of forced convection fraction had a strong correlation with the local Reynolds number in sloshing corium pools. Conclusively, the transient heat flux distribution of the sloshing melting pool differed from that of the static corium pool, increasing the molten range, and molten peak depth of the pressure-vessel-wall.