A self-driven two-phase cooling method based on phase-change pressurization in porous media: Thermal and transport characteristics

A self-driven two-phase cooling method (STCM) based on phase-change pressurization in prewetted porous media is experimentally investigated for high-temperature thermal management without external pumping. Boiling-induced vapor pressure drives vapor-rich two-phase fluid toward the outlet, forming a semi-open, finite-inventory transport process. Experiments are conducted at heat-source temperatures of 600 and 300 °C, an initial water mass of 145 g, and an atmospheric outlet. Four porous felts, different quartz glass fiber felt (QGFF) fill masses, and inclination angles from +90° to −90° are examined through wettability, capillary, microstructural, temperature, and pressure analyses. QGFF exhibits an apparent capillary-pressure scale of 1.271 kPa, approximately 8.6 times that of nano-aerogel felt, and provides the most favorable sustained temperature response among the tested materials. For QGFF fill masses of 8–12 g, the 10 g case achieves the best tested performance, extending the effective temperature-control duration to 3500 s. Inclination experiments show a non-monotonic orientation effect, while the phase-change-to-gravity pressure ratio remains above unity (approximately 4–24) whenever an axial gravity component exists, and transport persists at 0°. These results support phase-change pressurization as the primary driving force for cross-regional two-phase transport, while porous structure and gravity regulate the associated thermal response and transport behavior.