Enhanced dropwise condensation on heterogeneously hybrid patterned surfaces

Superhydrophilic and superhydrophobic hybrid (SSH) surfaces were developed to study the condensation heat transfer enhancement on copper substrates. The synergistic combination of superhydrophobic and superhydrophilic surfaces is conducive to enhancing droplet nucleation rate, well-controlled coalescence and efficient condensate removal. Three types of superhydrophilic and superhydrophobic hybrid surfaces were investigated, having pattern spacing (the distance between two superhydrophilic regions) of 300 μm, 600 μm, and 600 μm, and corresponding pattern dimensions of 600 × 600 μm2，600 × 600 μm2, and 800 × 800 μm2, named as SSH-1, SSH-2, and SSH-3, respectively. The experimental results revealed condensation heat transfer performance of hybrid surfaces outperformed than that of conventional complete superhydrophobic surface. The SSH-2 surface had the largest heat transfer coefficient under the entire range of surface subcooling. At a surface subcooling of 7.1 K, heat transfer coefficient of SSH-2 surface was 1.1 and 1.3 times than that of SSH-3 and SSH-1 surfaces, respectively. Pattern spacing could produce significant influence on the heat transfer performance of hybrid surfaces in relative to the influence of pattern dimension. Compared with complete superhydrophobic surface, the heat flux of SSH-2 surface was enhanced up to 31–73%.