Studies on the critical heat flux in fuel assembly using a modified two-phase multi-scale interface model—validation and sensitivity analysis

Abstract

Abstract The flow regime transition with the multi-scale interface is an important mechanism in the CFD simulation of boiling flow, especially in the saturated boiling and even departure nuclear boiling (DNB), while the current model is still immature. In this paper, a modified two-phase multi-scale interface model, which considering the concentration and morphology of interfacial area and the interfacial transfer of momentum, heat and mass, was compiled into the Eulerian two-fluid model in Fluent code to investigate the characteristics of two-phase flow. The improved model was validated systematically by the adiabatic two-phase flow data for different interface morphologies and the boiling flow data with different void fraction. And then the overall ability of the models in predicting the CHF values in a simplified fuel assembly was evaluated. The results showed that most predicting deviations were less than ±20%. Finally, the sensitivity of the empirical values in the modified two-phase multi-scale interface model was analyzed. In summary, the results proved that the modified two-phase multi-scale interface model based on two-fluid model could be used to simulate boiling flow with flow regime transition and was able to predict CHF in the fuel assembly reasonably.