Power plant cooling towers are responsible for significant evaporated water loss, thereby providing an excellent opportunity for water collection. Previous research by Ghosh et al. (2015) captured up to 66,000 gallons of cooling tower moisture on flexible meshes in the cooling tower of a 500 MW plant. However, water droplets on a stationary meshes and films must coalesce until droplets reach the departure size of 3–4 mm for gravity-driven flows. This work investigates the effects of flapping on water droplet coalescence and departure from a flexible film. Water droplets were sprayed onto stationary and flapping perflouroalkoxy (PFA) films with contact angles of 107 degrees. The frequency response of droplets to oscillations (approximately 10–100 Hz) was studied, and the influences of amplitude and acceleration were documented. High-speed videos were recorded to capture movement of water droplets from the front and side in order to view droplet motion and contact angle dynamics. Still images were processed in ImageJ; percent water area coverage was reduced on the flapping film after two seconds compared to the stationary film. Flapping promoted droplet coalescence and reduced droplet departure size to 1–2 mm on the flapping film, thereby clearing the film. Further understanding of droplet coalescence and motion is required before it can be applied to cooling towers. Ultimately, water collected from this system could utilized in the power plant or recycled for other industrial or agricultural uses.

Vibration-driven droplet motion on a flapping film for water collection

253rd National Meeting (2017)

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