Quantification of Nucleation Site Density as a Function of Surface Wettability on Smooth Surfaces

Abstract

AbstractDew water is recognized as a valuable source of clean water for human consumption. Given the developing concerns over global water scarcity, great focus has been turned toward increasing the efficiency of existing dew harvesting methodologies. Droplet nucleation is a critical first stage in the condensation process – and therefore key to dew water harvesting. In this paper, the droplet nucleation site density (Ns) as a function of surface wettability on smooth thin polymer films is quantified. A custom‐built environment chamber, operated in low supersaturation conditions relevant to atmospheric water harvesting, allows strict experimental control over temperature and humidity. Droplet growth through coalescence is quantified, and an exponential increase in the rate of coalescence is seen as the test surface wettability increased. Ns declines exponentially as wettability decreases according to the fitted equation Ns = 1.1 × 1011e−0.043θ , where theta is the contact angle of the smooth surface, which can be used to predict Ns from a known contact angle, currently not available. The average distance between droplet centers is found to increase at a linear rate. This nucleation behavior is in line with those of droplets in a Rayleigh distribution.