Experimental and theoretical research on the effect of branch size on the gas entrainment

Abstract

The existing research on gas entrainment is mostly performed on the background of a SB-LOCA on hot legs or cold legs, that is, the models are established on the basis of the experiments of entrainment through a small downward branch/break (d/D ≤ 0.2). For the gas entrainment through a large size downward branch, relevant research is rare. Therefore, in order to investigate influence of branch size on the gas entrainment, two visualized entrainment experiments are conducted on the basis of a large size (d/D = 0.625) and a small size (d/D = 0.1) downward branch pipes in this paper. The phenomena of entrainment through a large size branch and a small size branch are different. Gas chamber can be observed for beginning of entrainment through a large size branch, and a new entrainment process can be found for entrainment through a large size branch. Also, two new correlations considering the effect of branch size for separately predicting the onset of gas entrainment and the branch quality are developed with maximum relative error less than 10% and 25%, respectively.