Experimental investigation of the film boiling heat transfer in HeII: Heat transfer coefficient

He 11 film boiling is of both academic and applied interests. However, information about He 11 film boiling is still inadequate and further study is needed from both the technical application and the scientific aspects. In the present study, a thin stainless steel foil heater (10 pm thick) is employed to induce boiling in He II. The average heater surface temperature is measured to evaluate the heat transfer performance of He 11 film boiling under different thermal conditions. And meanwhile, the pressure and the temperature oscillations induced by the film boiling are also measured. It is found that the pressure oscillation and the temperature oscillation highly correlate with each other, which indicates that the vapor bubble is vibrating on the heater surface during film boiling. The heat transfer coefficient of the film boiling depends on both the pressure over the heater surface and the He 11 bath temperature. The heat transfer coefficients of three kinds of boiling states: noisy film boiling, transition boiling and silent film boiling, are measured in the present study. The visualization of the boiling process is also carried out. (C) 2004 Elsevier Ltd. All rights reserved.