Study of film boiling in He II by pressure and temperature oscillation measurements

Abstract

In the present study, the discussion on film boiling states in He II is presented on the basis of some new experimental results. Experiments were conducted under various thermal conditions, e.g., different bath temperature, immersion depth and heat flux. In subcooled film boiling state, a flame-shaped vapor bubble is seen to be quivering on a planar heater accompanied with a little audible noise, and the pressure oscillation is detected, which results from both vapor bubble oscillation and liquid column oscillation of bulk He II in a cryostat. In noisy boiling state in saturated He II, a big vapor bubble grows and erupts repeatedly on a planar heater accompanied with a large acoustic noise, and the pressure oscillation is mainly caused in accordance with vapor bubble crush and formation. A three-dimensional boundary map indicating different boiling states is constructed by taking account of effects of the bath temperature and the heat flux as well as the hydrostatic pressure. Temperature oscillation during noisy film boiling is also measured by the aid of superconductor temperature sensors. It is found that the large temperature rise is caused by both the passage of thermal boundary layer and repeated expansion and crush of a vapor bubble on the planar heater.