Influence of wettability on water-vapor condensation over plain and microporous coated surfaces

Condensation experiments with saturated water vapor at 1 atm are performed on 50 mm by 50 mm High Temperature Conductive Microporous Coating (Cu-HTCMC) surfaces in three wettability states: pristine ( θ ≈ 0 ° ), oxidized parahydrophobic ( θ ₐ ≈ 117 ° / θ ᵣ ≈ 0 ° ), and Teflon-coated hydrophobic ( θ ≈ 136 ° ) and presented alongside plain hydrophilic and hydrophobic references. The Cu-HTCMC was created by sintering of copper powders with the average particle size of 67 µm and about 232 µm coating thickness. Pristine and oxidized surfaces exhibit filmwise heat-transfer coefficients that closely follow Nusselt’s theory, showing complete wetting performance regardless of surface structure. The hydrophobic Teflon-coated Cu-HTCMC sustains partial intrapore wetting and delivers up to 2.3 times higher heat-transfer coefficients than the pristine fully wetted coating and 2.2 times higher than oxidized Cu-HTCMC surfaces, outperforming plain hydrophobic surfaces. The Teflon coating, produced via a robust two-step curing process, exhibited excellent durability and maintained its hydrophobicity throughout the condensation tests. These findings demonstrate that combining microporous morphology with tailored wettability significantly enhances condensation heat transfer, offering a new pathway for designing high-performance thermal management surfaces.