Enhancing Air-Water Gas Transfer Using Capillary-Gravity Wakes

Air-water gas transfer rate limits some industrial processes, such as algae biofuel production. This limitation can be overcome through methods such as bubbling, waterfalls, or jets. However, these solutions are energy-intensive and disruptive. Therefore, this research explores more energy-efficient hydrodynamic means to enhance the transfer rate of low-soluble gases. Previous studies found that wind- or vibration-driven short-wavelength waves contribute to interfacial mass transport by straining the concentration boundary layer and increasing surface area. This presentation describes laboratory experiments conducted in a straight, open flume to determine the impact of capillary-gravity wakes on air-water gas transfer. An array of 1/8” dowels was partially submerged to disturb the water surface and form rippling wakes. The Bond number (BO_D=D/λ_c) varied between 0.5 and 0.8, and the Froude number (Fr=U/√(gD)) varied between 1.8 and 2.0. During these experiments, the gas transfer velocity was 20-24% higher than the control case. Energy loss is estimated based on mean streamwise slope of the free surface. Further studies will modify dowel density and configuration and relate gas transfer enhancement to BO_D and Fr.