Criticality in the slowed-down boiling crisis at zero gravity

Area of Science:

• Thermodynamics
• Fluid Dynamics
• Phase Transitions

Background:

• Boiling crisis signifies a transition from nucleate to film boiling at critical heat flux (CHF).
• Traditional studies face challenges due to high CHF and rapid transition dynamics (under 1 ms).
• Experiments in hydrogen near its critical point offer a unique opportunity to study low CHF and slow dynamics.

Purpose of the Study:

• To investigate boiling crisis phenomena under conditions of low critical heat flux and slow dynamics.
• To analyze the structure and behavior of dry spots preceding boiling crisis.
• To examine the influence of reduced gravity on boiling crisis dynamics and critical heat flux.

Main Methods:

• Experiments conducted using two-phase hydrogen near its liquid-vapor critical point.
• Artificial weightlessness achieved by compensating gravity with magnetic forces in reduced gravity.
• High-resolution observation and statistical analysis of dry spot formation and fractal structures.

Main Results:

• Revealed a fractal structure in the contour of dry areas preceding the boiling crisis.
• Confirmed boiling crisis in zero gravity as a scale-free phenomenon through statistical analysis of dry spot areas.
• Observed that saturated boiling critical heat flux tends towards zero in zero gravity, aligning with theoretical predictions.

Conclusions:

• Boiling crisis dynamics can be resolved and analyzed in detail under specific low-CHF conditions.
• The scale-free nature of boiling crisis in zero gravity provides new insights into its fundamental mechanisms.
• Reduced gravity significantly impacts boiling crisis, suggesting potential for crisis observation at lower heat fluxes with extended experimental durations.