The implementation of the drift-flux interfacial friction model into TRAC-PF1 is described. The model is based on a set of best-estimate drift-flux correlations which cover the full range of geometries and flow conditions encountered in PWR safety analysis. The correlations are converted into the effective interfacial friction coefficient that can be applied in the code for transients as well as steady-state conditions. The finite difference equations are derived in the form of TRAC-PF1 to include the drift-flux interfacial friction model and constitutive equations which are based on Putney’s work.
The validation of the modified code is performed using the experimental data from the GE level swell test and the ORNL THTF test, respectively. The predictions by modified TRAC-PF1 for the GE level swell test show slightly better than those by TRAC-PF1. The predictions by modified TRAC-PF1 for the ORNL THTF test are in excellent agreement with the measured data and represents a significant improvement over those produced by TRAC-PF1.