Boiling heat transfer through a porous medium offers an attractive combination of enormous liquid-vapor interfacial area and high bubble nucleation site density. In this work, we characterize the boiling performances of porous media by employing the well-ordered and highly interconnected architecture of inverse opals (IOs). The boiling characterization identifies hydrodynamic mechanisms through which structural characteristics affect the boiling performance of metallic microporous architecture by validating empirical measurements. The boiling performances can be optimized through the rational design of both the structural thicknesses and pore diameters of IOs, which demonstrate up to 336% enhancement in boiling heat-transfer coefficient (HTC) over smooth surfaces. The optimal HTC and critical heat flux occur at approximately 3-4 μm in porous structure thickness, which is manifested through the balance of liquid-vapor occupation within the spatial confinement of the IO structure. The optimization of boiling performances with varying pore diameters (0.3-1.0 μm) can be attributed to the hydraulic competitions between permeability and viscous resistance to liquid-vapor transport. This study unveils thermophysical understandings to enhance multiphase heat transfer in microporous media for ultrahigh heat flux thermal management.
Keywords: 3D microporous architecture; boiling heat transfer; inverse opals; parahydrophobicity; wettability.