Condensation Dynamics and Droplet Size Distribution

Condensation phenomena are important for several engineering fields including HVAC, refrigeration, distillation/desalination of water, dehumidification, aerospace, and water harvesting applications. In this work, Microsphere Photolithography (MPL), a low-cost, bottom-up fabrication technique, was used for fabricating a silica nanopillar surface (0.7 μm to 1.2 μm pillar diameters in a 2 μm hexagonal close packed array) on silicon. Condensation experiments on the surface was studied under the influence of environmental factors (ambient temperature and relative humidity) and substrate characteristics (topology and temperature). Droplet growth dynamics and size distribution were explored for condensation on a plain silicon substrate and a fabricated hydrophilic nanopillar substrate at different relative humidities (40% and 60%) at a surface temperature of 5°C. It was revealed that the nanopillar surfaces have a profound impact on condensation behavior. Small coalescence dominated on the silicon substrate as opposed to the nanopillar substrate, where extensive pinning deters the merging of droplets until it touches neighboring droplets. The change in condensation dynamics creates favorable conditions for collection of water.