Atmospheric water generators (AWGs) provide a promising route for producing potable water directly from humid air; however, their performance is often limited by inefficient condensation and slow removal of condensate from condenser surfaces. In this study, a scalable hybrid wettability strategy was developed to enhance condensation heat transfer and condensate management on tubular copper condensers. Patterned copper surfaces with alternating hydrophilic (HP) and hydrophobic (HB) domains were fabricated using photochemical FeCl 3 etching followed by n -octadecyl mercaptan ( n -ODM) functionalization. Morphological characterization confirmed the formation of well-defined etched microstructured regions, while n -ODM functionalization effectively tailored the surface wettability without introducing significant thermal resistance. A systematic parametric investigation was conducted to evaluate the influence of wettability patterns on condensation heat transfer and droplet dynamics under near-atmospheric saturation conditions in the presence of noncondensable gases. The optimized hybrid surface, comprising alternating 1 mm hydrophilic and 2 mm hydrophobic domains, achieved a heat flux of 590 kW m –2 and a condensation heat transfer coefficient (HTC) of 93 kW m –2 K –1 at a subcooling temperature of 9 °C. This corresponds to a 1.3-fold enhancement over filmwise condensation on a fully hydrophilic surface and a 1.2-fold improvement over dropwise condensation on a fully hydrophobic surface. Wettability characterization, contact angle hysteresis analysis, and time-resolved visualization revealed that the wettability contrast promotes capillary-assisted condensate transport toward the hydrophilic drainage channels, enabling rapid liquid removal and continuous regeneration of active condensation sites. Furthermore, the patterned surface maintained stable wettability contrast and condensation performance during 100 h of cyclic condensation-drying operation, demonstrating its durability under prolonged working conditions. These results highlight the potential of hybrid wettability engineering as a simple, scalable, and energy-efficient strategy for enhancing condenser performance in next-generation AWG systems.
Govindaraju et al. (Mon,) studied this question.