Improvement of entrainment model for horizontal flow in ATHLET and application to Mantilla experiment and TPTF

The entrainment correlations proposed by Al-Sarkhi & Sarica (2013) and the modified Pan & Hanratty (Lee, 2022) were newly implemented in ATHLET to improve the entrainment model for horizontal flows. In addition, the criterion for the onset of entrainment was adjusted with the model suggested by Ishii & Grolmes (1975). The implemented models were examined by simulating two horizontal two-phase flow experiments, the Mantilla experiment and TPTF, in the frame of a benchmark activity of FONESYS. The Mantilla experiment consisted of 2 -inch and 6-inch diameter pipes, and it was conducted with air-water mixtures at -2 bar pressures and -20 degrees C temperatures. On the other hand, TPTF had 4-inch and 8-inch diameter test sections, and it was performed with highly pressurized steam-water mixtures in 30 - 86 bar. It turns out that the Al-Sarkhi & Sarica model could improve the prediction of entrainment for the 2-inch Mantilla test section, but it predicted much higher entrainment fractions for the 6-inch Mantilla test section and TPTF. On the other hand, the modified Pan & Hanratty correlation could achieve significant improvements for the entrainment prediction for both the Mantilla experiment and TPTF. Regarding the onset of entrainment, the Ishii & Grolmes criterion was able to yield a slightly better prediction than the ATHLET built-in model for high-pressure cases of TPTF.