Characteristics of jumping droplet-enhanced condensation on nanostructured micromesh surface

Jumping-droplet enhanced condensation has recently attracted huge interest due to its remarkable potential of heat transfer performance enhancement, and studies have been done to design superhydrophobic surfaces with various surface morphologies. We fabricated a superhydrophobic micromeshcovered surface using a facile and scalable method. ESEM condensation experiment results show that droplets in pores formed by the mesh wires had faster growth rate in the upward direction than droplets on wires. This is mainly because of the confining role of the wires and higher heat transfer rate due to larger solid-liquid contact area. Also, these droplets always jumped at the size of pores (∼35 μm) when they coalesced with other droplets on wires. Moreover, droplets in pores were distorted by mesh wires, resulting in larger surface area. Theoretical predictions show, for a specific droplet radius, coalescence jumping of distorted droplets on the mesh-covered surface releases more excess surface free energy, and has larger jumping velocity than that of spherical droplets on the plate surface without mesh. This better performance was further validated by constant exposure of those two surfaces to electron beam during which work of adhesion was gradually increased. As expected, droplets on the mesh-covered surface coalesced and jumped while coalescing droplets on the plate surface could not as the exposure time increased. Our results offer new insights for designing hierarchical structured superhydrophobic surfaces to further enhance the performance of condensation heat transfer processes.