An inter-channel mixing model based on the void distribution in a rod bundle

Abstract

Turbulent mixing effect is crucial for coolant subchannels in a nuclear reactor, as it directly influences flow distribution and cooling capacity. The enthalpy in the hottest channel is reduced in this way, thus improving the location of critical heat flux (CHF) to some extent. In order to predict CHF accurately, the inter-channel mixing model is incorporated into the subchannel analysis code to simulate thermal-hydraulic phenomena during a reactor operation. In this paper, a novel inter-channel mixing model has been developed through extensive investigation of experimental research. In addition, the power-law profile is considered for predicting the void distribution resulting from the void drift effect. Finally, the developed mixing model is embedded in a subchannel analysis code, and pressurized water reactor sub-channel and bundle tests (PSBT) data are selected as a benchmark for the model validation. The simulation results show that the current mixing model can accurately predict void fraction and thermal equilibrium quality at specific axial locations with absolute errors of 0.1 and 0.04, respectively.