Energy mode change between second sound thermal pulse and evaporation wave in the vicinity of free surface of superfluid He II

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The energy balance across a phase boundary is important for the consideration of evaporation phenomena from a free surface of superfluid helium. The super thermal conduction as a heat transport mechanism, second sound thermal pulse and quantized vortices that impede the heat transfer must be included into a quantitative consideration. In order to clarify the phenomena, a number of relating physical phenomena are experimentally investigated.1.Evaporation upon an oblique incidence of a thermal pulse on a He II free surface : It had been reported that fairly good agreement had resulted between a theoretical prediction on the basis of the energy balance among an incident thermal pulse, a reflecting thermal pulse and evaporation wave with the present experimental result with an error of only 5%, but a complete agreement had not been attained. The discrepancy was supposed to arise from the effects of reflecting first sound compression wave and presumably a ripron, but the present experiment could not reveil the cause. In the case of thermal pulse incidence with a large incident angle, a total reflection occurred, though the total reflection was observed only at the wave front but was not observed in the uniform portion behind the wave front.2.Cavitation flow of He II : Fundamental differences are found between cavitating flows of He I and He II. It is concluded that these are primarily caused by the difference in the heat transfer mechanisms, the super thermal conduction in He II and the thermal conduction in He I. Even a lambda phase transition is induced because of large temperature drop caused by cavitation.3.He II boiling : There appear a noisy and silent film boiling modes under nearly saturated vapor pressure condition, and a number film boiling modes in subcooled He II.4.Superfluid shock tube : It is observed large scale evaporation and subsequent condensation occur upon an incidence of a gas dynamic shock wave on a He II free surface.