Van Air WC series water-cooled after-coolers use water as a cooling medium. The cooling medium flows counter-currently through a shell and tube liquid-to-air heat exchanger. Countercurrent flow provides the most effective method of bringing the final compressed air temperature close to the cooling medium temperature. The air to be cooled is directed through multiple tubes. Each tube is helically enhanced to substantially increase the heat transfer capability over a plain tube. For example, compressed air is discharged from a compressor at 250°F and enters a Van Air WC series after-cooler sized for a 15°F approach to 75°F cooling. Air will leave the after-cooler at 85°F, and water condensed by cooling from 250°F to 85°F is separated out.

The WC series after-coolers are compact. Standard models are 51" long, and high efficiency models are 59" long. In both fixed and removable tube bundles, the tubes are welded to the tube sheet. This, combined with the short length, results in a rugged unit that allows thermal expansion to be absorbed within the after-cooler. Standard materials of construction are copper tubes with carbon steel shells.