Development of gas entrainment evaluation method considering three-dimensional pressure decrease distribution along the center of free surface vortex

Matsushita, Kentaro  ; Ezure, Toshiki ; Imai, Yasutomo*; Fujisaki, Tatsuya*; Tanaka, Masaaki  

In design of sodium-cooled fast reactors (SFRs), cover gas entrainment phenomena induced by vortex dimple at free surface in upper plena is an important thermal-hydraulic issue. Authors have developed an evaluation method of gas entrainment with an evaluation tool named "StreamViewer". In this study, modification of evaluation model to improve quantitatively prediction accuracy of gas core length was investigated. In this model, vortex center lines which elongated from suction port where entrance of gas to heat transport system, for instance, IHX inlet in pool type SFRs, to free surface in plenum were to be identified, and distribution of pressure decrease along vortex center line was calculated to judge possibility of gas entrainment in comparisons with hydraulic head. This evaluation model was applied to results of water experiment with a rectangular open channel, where unsteady vortices are generated. It was confirmed that this model can identify occurrence of gas entrainment.