Experimental study on drift flux correlation formulas for two-phase flow in large diameter tubes

The correlation formulas correctly expressing the velocity difference between steam and water of two-phase flow are required for accurate predictions of the thermal hydraulic transient behaviours of the Pressurized Water Reactor (PWR) power plant during a small break loss of coolant accident (LOCA). The drift flux model is one of the typical models which describes the relative velocity between the two phases. A number of empirical formulas of the drift flux model have been proposed based on the experiments. It is necessary to confirm whether those formulas are applicable to the simulation of the two-phase flow behaviour in the large scale apparatus like the actual PWR plant also. The experiments of cocurrent and counter current steam-water two-phase flow using the large scale apparatus with 0.1023 m diameter tubes and the small scale apparatus with 0.0197 m diameter tubes were carried out. This paper presents the tube diameter effects on the drift flux parameters (Co and Vgj) and new empirical drift flux correlation formulas for the two-phase flow in large diameter tubes are proposed. (author)