Recent research suggests that hydrophobic surfaces can have 5-7 times the heat transfer coefficient of laminar film condensing. This invention consists of employing hydrophobic condensing in AGMD. In typical AGMD, a hot saline feed side passes a hydrophobic membrane, which allows hot water vapor through but not saline liquid water. The vapor crosses an air gap and is condensed on a condensing surface. The condensing surface may be cooled by a cold stream, or in multistage configurations, feed streams at progressively lower temperatures.
The inventors paired superhydrophobic condensation surfaces with untreated and superhydrophobic air gap support meshes of high and low conductivities to determine optimum conditions for energy efficient permeate production in AGMD. They determined that introducing superhydrophobic surfaces can result in an up to 110% improved efficiency for AGMD desalination. Superhydrophobic condensation conditions at varied feed and cold side temperatures are recommended for substantial improvement for AGMD systems.