SIMMER-III Analysis, of Gas-Liquid Flow with Large Liquid Density

Suzuki, Toru; Tobita, Yoshiharu

The transition phase analysis code SIMMER-III has been developed to appropriately evaluate the core disruptive accident in a fast breeder reactor. The momentum exchange model used in the fluid dynamics portion of the code uses the conventional correlation based on ordinary flows such as air-water flows. lt has already been confirmed that this code can represent the experimental results of ordinary flows. However, more detailed research is needed to confirm that this code is applicable to two-phase flow with large liquid density, which would be formed in an actual molten core pool. In addition, since the shapes of bubbles affect their drag in the bubbly flow where the liquid and the gas form continuous and dispersed phases, respectively, it is necessary to take this effect of bubble shape into account to improve SIMMER-III's analytical precision. ln this study, using experimental results obtained through a joint research program with Kyoto university, the momentum exchange model of SIMMER-III is assessed with regard to the bubbly flow regime of two-phase flow with large liquid density, on which experimental data and information on bubble shapes had been lacking. This study suggests that the original SIMMER-III can appropriately represent the characteristics of bubbly flows containing ellipsoidal bubbles with relatively small gas flux. Moreover, this study shows that the precision of SIMMER-III for bubbly flows containing cap bubbles with relatively large gas flux is much improved by using Kataoka-lshii's correlation to determine the drag coefficient of bubbles in the momentum exchange model.