Numerical Study of Two-Phase Flow of Liquid Helium in a Vertial Converging-Diverging Nozzle

The fundamental characteristics of the two-dimensional gas-liquid two-phase flow of liquid helium through a vertical converging-diverging duct near the lambda point are numerically investigated to realize the further development and high performance of new multiphase superfluid cooling systems. First, the governing equations of the two-phase flow of liquid helium based on the unsteady thermal nonequilibrium multifluid model with generalized curvilinear coordinates system are presented, and several flow characteristics are numerically calculated, taking into account the effect of superfluidity. Based on the numerical results, the two-dimensional structure of the gas-liquid two-phase flow of liquid helium though vertical converging-diverging nozzle is shown in detail, and it is also found that the geneation of superfluid counterflow against normal fluid flow based on the thermomechanical effect is conspicuous in the large gas phase volume fraction region where the liquid-to vapor-phase change actively occurs. Furthermore, it is clarified that the mechanism of the He I to He II phase transition caused by the temperature decrease is due to the deprivation of latent heat for vaporization from the liquid phase.