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Entropy Generation Analysis of the Flow Boiling in Microgravity Field
Zijian Sun1, Haochun Zhang1, Qi Wang1
1School of Energy Science and Engineering, Harbin Institute of Technology, Harbin 150001, China.
Entropy (Basel, Switzerland)
|April 23, 2022
Summary
This study develops a new model for entropy generation during flow boiling in microgravity, analyzing heat flux and velocity effects on irreversibility. Critical heat flux (CHF) is identified as optimal for thermodynamic efficiency.
Area of Science:
- Thermodynamics
- Fluid Mechanics
- Heat Transfer
Background:
- Flow boiling in microgravity presents unique challenges for thermodynamic analysis.
- Understanding entropy generation is crucial for optimizing energy systems.
Purpose of the Study:
- To develop a novel entropy generation model for microgravity flow boiling.
- To investigate the influence of heat flux and velocity on irreversibility.
- To evaluate boiling performance using established and new metrics.
Main Methods:
- Numerical simulations using ANSYS-FLUENT.
- Development of a phase-change model validated against the Stefan problem.
- Analysis of entropy generation components: heat transfer, viscous dissipation, turbulent dissipation, and phase change.
Main Results:
- Local entropy generation varies significantly based on phase conduction and evaporation near the wall.
- Entropy generation and the Bond number (Be) increase with heat flux, with heat transfer becoming dominant.
- Boiling status transitions exhibit velocity-dependent trends impacting irreversibility.
Conclusions:
- The study provides insights into optimizing flow boiling processes in microgravity.
- Critical heat flux (CHF) represents a thermodynamically optimal operating point.
- The developed model and metrics aid in performance evaluation and system design.
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