By Josh Perry, Editor
[email protected]

Scientists from the University of Colorado Boulder, Huazhong University of Science and Technology, Beijing Jiaotong University, and Dalian University of Technology have developed a superhydrophobic hierarchical mesh-covered surface that enables continuous sucking flow of liquid condensate and enhances heat transfer through condensation.

Researchers have found a method for enhancing heat transfer through condensation. (Science China Press)

According to an announcement from Science China Press, the researchers started with a commercially-available copper woven mesh that was bonded with a plain copper substrate. Copper oxide nanostructures form on the exposed surfaces of the substrate and mesh wires and act as sites for droplet formation and growth.

“During vapor condensation, the nucleated droplets on the substrate rapidly grow and coalesce to form a thin liquid film in the interconnected channels between the substrate and woven mesh layer,” the article explained. “When small droplets growing on the mesh wires merge with the thin liquid film, they can be efficiently removed by being pulled into the liquid film, accelerating surface refreshing for droplet re-nucleation and growth on the mesh wires.”

This enables the interweaving channels to be filled with condensate and the liquid film is continuously drawn out of the mesh and forms droplets on the surface of the device. This means there is constant refreshing on the surface to improve thermal performance.

According to the article, “This work significantly advances the field of condensation heat transfer enhancement including the scalable-manufactured materials, novel liquid removal mechanism, and unprecedented heat transfer enhancement. In particular: (1) a superhydrophobic hi-mesh surface that can be scalably manufactured is fabricated using low-cost commercial meshes; (2) a novel sucking-flow liquid removal mechanism is demonstrated to promote both surface refreshing and droplet growth; (3) Unprecedented condensation heat transfer enhancement is demonstrated over a wide range of surface subcooling, compared to state-of-the-art dropwise condensation on other micro/nanostructured surfaces.”

The research was recently published in National Science Review. The abstract stated:

“Controlling the solid-liquid-vapor tri-phase interface is of fundamental importance for a broad range of industrial applications ranging from biomedical engineering, energy production and utilization, environmental control, water production, and thermal management. Despite that a lot of progress has been made over the past few decades on surface manipulation for promoting droplet removal, it is challenging to accelerate both droplet growth and surface refreshing for enhancing vapor-to-liquid condensation.

“Here we present a superhydrophobic hierarchical mesh-covered (hi-mesh) surface to enable continuous sucking flow of liquid condensate, which achieves fourfold-higher droplet growth and 36.8% faster surface refreshing compared to the state-of-the-art dropwise condensation. Unprecedented enhanced condensation heat transfer is observed to sustain over a wide range of surface subcooling on the hi-mesh surfaces.

“This demonstration of sustaining enhanced condensation enhancement is not only of fundamental scientific importance, but also provides a viable strategy for large-scale deployment of micro/nanostructured surfaces in a diverse range of technologies.”