Removal of droplets driven by orthogonal gradient grooves during dropwise condensation

The vitality to microstructure design lies in utilizing deformation to accumulate surface energy and facilitate droplet rebound. This passive strategy effectively restricts the size of surface droplets, modifies condensate droplet distribution and coverage, and thereby enhances heat transfer efficiency. Thus, the development and fabrication of innovative microstructures with enhanced self-propulsion for efficient surface renewal emerges as a promising approach. In this study, we propose the design and fabrication of a condensing surface with an orthogonal gradient groove structure, which demonstrates a superior driving force compared to conventional single gradient grooves, such as V-shaped and wedge-shaped gradient grooves. We establish an experimental platform for visualization of droplet dynamics and heat transfer measurement. The results indicate that the orthogonal gradient groove surface significantly enhances the driving force, especially under high subcooling in humid air, facilitating droplet relay jumping and Laplace-driven sweeping to refresh the surface and reduce droplet accumulation. When ΔT = 25 °C, the heat flux of OGGS reaches its peak at 3008.4 W/m2, which is 18.72 % higher than that of WGGS, 13.72 % higher than that of VGGS, and 34.39 % higher than that of SGS.