Boiling Crisis Dynamics: Low Gravity Experiments at High Pressure
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To understand the boiling crisis mechanism, one can take advantage of the slowing down of boiling at high pressures, in the close vicinity of the liquid-vapor critical point of the given fluid. To preserve conventional bubble geometry, such experiments need to be carried out in low gravity. We report here two kinds of saturated boiling experiments. First we discuss the spatial experiments with SF 6 at 46 ∘C. Next we address two ground-based experiments under magnetic gravity compensation with H 2 at 33 K. We compare both kinds of experiments and show their complementarity. The dry spots under vapor bubbles are visualized by using transparent heaters made with metal oxide films. We evidence two regimes of the dry spots growth: the regime of circular dry spots and the regime of chain coalescence of dry spots that immediately precedes the heater dryout. A recent H 2 experiment is shown to bridge the gap between the near-critical and low pressure boiling experiments.
KeywordsCHF Boiling cisis Departure from nucleate boiling Bubble growth
The financial support of CNES within the fundamental microgravity research program and two EMFL grants that covered usage of the LNCMI magnet facility are acknowledged. The authors are grateful to J. Chartier and P. Bonnay of SBT for the help with the development and technical support of the magnetic gravity compensation experiments and to E. de Malmazet for the initial design of the LHYLA cell. We acknowledge the support of the LNCMI, member of the European Magnetic Field Laboratory (EMFL). We thank the whole CNES-DECLIC team and in particular G. Pont for their enthusiastic and helpful involvement in this work.
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