Improvement of gas entrainment evaluation method. Introduction of surface tension effect

A gas entrainment (GE) evaluation method was presented at NTHAS5 to propose design criteria of sodium-cooled fast reactor systems. In that presentation, the GE evaluation method was confirmed to give reasonable gas code length values by simple evaluation procedures. However, in the GE evaluation method, surface tension effects were neglected for simplification. In this research, the analytical accuracy of gas core lengths is improved by introducing the surface tension effects into the GE evaluation method. For that purpose, first, the mechanical balance between gravitational, centrifugal and surface tension forces is considered and second, the shape of a gas core tip is approximated by a quadratic function. Finally, using a curvature calculated from the approximated gas core shape, we can determine the gas core length satisfying the mechanical balance. This improved GE evaluation method for gas core lengths is validated by analyzing the gas core lengths observed in basic experiments. As the results, the analytical gas core length values by the improved GE evaluation method become shorter and give better agreements with the experimental data than the original GE evaluation method. In addition, the experimental data under different temperature and surfactant concentration conditions are reproduced by the improved GE evaluation method. (author)