Evaluation of turbulent mixing between subchannels with a CFD code

This study describes the procedure to determine the turbulent mixing coefficients from the numerical simulation of subchannel flow. The turbulent mixing coefficient is important to predict the detailed flow and temperature distributions in the reactor core. The mixing coefficient for the design condition of KALIMER-600 has been evaluated and compared with the results from the existing correlations. The data determined numerically are in good agreement with the correlations based on the thermal methods or the tracer methods. However, the data shows quite large deviations from the correlations obtained with the turbulent fluctuation of momentum. This discrepancy mainly comes from the confusion in the definition of eddy diffusivity. The numerically obtained data are meaningful because the data for liquid metal are scarce. The ultimate goal of the analysis is the development of a mixing correlation to improve the accuracy of the whole core thermal hydraulics model. (author)