Effects of difference in wettability level of biphilic patterns on copper tubes in pool boiling heat transfer

This study experimentally investigated pool boiling heat transfer on copper tubes for superhydrophilic surfaces with square patterns of different wettability levels. Deionized (DI) water was used as a working fluid. A silica-based coating mechanism and the picosecond (ps) laser system were combined to fabricate samples with different surface wettability levels. The contact angle values of four types of samples were in the range 0°–150°. The boiling experiments were conducted under ambient conditions up to a maximum heat flux regime of 418 kW/m² and a saturated working fluid. Compared with the homogeneous plain copper surface, the heat transfer coefficient of the biphilic surface with hydrophobic patterns was enhanced up to 1.16, whereas that with superhydrophobic patterns decreased to 0.83 at the highest evaluated heat flux (418 kW/m²) because surface wettability led to different bubble dynamics. Bubble dynamics, on different samples were analyzed through high-speed imaging at three intervals of heat flux.