Assessment of an entrainment model in annular-mist flow for a three-field TRAC-M

A three-field model for annular-mist flow regime was developed and directly implemented into the one-dimensional components of TRAC-M/F90. The three-field model implemented in the present study was firstly developed based on the physical models of COBRA-TF. In the development of the present three-field model, the empirical correlations including entrainment and de-entrainment models in the literature were investigated and tested with the three-field model implemented in TRAC-M/F90. The entrainment model was assessed using Kataoka and Ishii's and Würtz's models. The use of Würtz's entrainment model shows excellent agreement with high pressure, steam/water experiments, while considerable scattering was observed in low pressure, steam/water and low pressure, air/water experiments. Kataoka and Ishii's model was found to be the best application in air/water, porous-sinter cases. Because of the narrowness of the applicability of Kataoka and Ishii's model, Würtz's model was selected as the base model for entrainment rate. The final combination of the empirical correlations is suggested and validated against steam–water experiments of various conditions. The agreements with experimental data were at 25.0% RMS error.