Pool boiling investigation on copper foam with heterogeneous wetting vapor channels

This study presents a pool boiling experimental investigation of copper foam microchannels with engineered heterogeneous wettability conducted under atmospheric conditions. Copper foam microchannels with spatially varied wetting properties were fabricated using immersion and welding methods. Two specific configurations were developed: one featuring super hydrophilic channel walls with a super hydrophobic bottom surface (SHPiW–SHPoB), and the other comprising superhydrophobic walls combined with a super hydrophilic bottom surface (SHPoW–SHPiB). By experiments, the effects of wettability heterogeneity on boiling heat transfer performance were systematically evaluated. It is found that the SHPiW–SHPoB configuration demonstrates a superior critical heat flux (CHF) of 108.2 W/cm², compared to 96.7 W/cm² for the SHPoW–SHPiB. Further experimental results show that the SHPiW–SHPoB configuration offers significantly improved pool boiling characteristics, indicating the potential of the wettability patterning for advanced thermal management of energy systems. The experiments suggest that the enhanced boiling performance of the SHPiW–SHPoB is attributed to the efficient separation of vapor and liquid flow paths enabled by the heterogeneous wetting design, which promotes bubble nucleation at low heat fluxes and suppresses bubble coalescence at high heat fluxes.