Development of interfacial friction model for two-fluid model code against countercurrent gas-liquid flow limitation in PWR hot leg

Abstract

An interfacial friction model for two-fluid model code has been developed for the countercurrent gas-liquid flow limitation at hot leg in a pressurized water reactor. Firstly, using a typical two-fluid model code TRAC-PF1/MOD1, we analyzed whether the interfacial friction model under countercurrent stratified flow by Ohnuki et al., which has been verified with an envelope model at steady state, functions well for the dynamic calculation with the two-fluid model code or not. It was found from the analyses that the model by Ohnuki et al. should be combined with a suitable interfacial friction model for the slug flow regime in hot leg. Based on flow observation in a small scale air-water experiment, models at the bend of hot leg and in the roll wave regime in the horizontal flow path of hot leg were newly developed as the model in the slug flow regime and the slug flow model was combined with the model by Ohnuki et al.. The validity of the present model was confirmed with the data under various conditions of scales, pressures and fluid combinations (inner diameter: 0.025 approximately 0.75 m, pressure; 0.1 approximately 7.1 MPa and air-water or steam-water).