HOW A REFRIGERATED AIR DRYER WORKS
(The most popular method)
Compressed air runs through a series of copper or alloy tubes which are in turn submerged in a refrigerant or heat extracting liquid. The heat is removed with a fan blowing across a heat exchanger. This heat is usually returned to the compressed air after it has dried the saturated air by the reverse of the latter method. This is a form of energy return.
The principle is simple enough. If you chill the air down to +2oC then you cannot extract anymore water from the compressed air unless you operate air equipment in a lower temperature. Since most factories require at least 16oC to satisfy a good working environment, it stands to reason the compressed air will not shed any moisture. Most refrigerated dryers operate between +2 and +5oC. This is called “Pressure Dew Point”. The dryer cannot drop to 0oC because the trapped moisture would freeze and block the air supply. Desiccant dryers overcome this problem and can produce a dew point of -70oC.
Please note: Moisture in compressed air causes rust, clogging and of course can freeze in the air lines during winter. This can lead to a multitude of problems, some of which are inevitably dangerous.