The principal of an air dryer by refrigeration is to separate the moisture in the air by bringing down the temperature of the compressed air by a thermal exchanger to a point called the ‟DEW POINT”.

So it’s a dry air, at a temperature said to be the dew point that is projected in the compressed air

network. This compressed air can be clean and oil-free if a pre-filter is installed before the inlet of the

dryer. Standard units are 25 SCFM , ¾” NPT, 115 VAC to 200 SCFM, 1 ½” NPT, 230 VAC.

The duty of the desiccant is to bring the pressure dew point of the compressed air to a level in which the water will no longer condense, or to remove as much water from the compressed air as possible. A standard dew point that is expected by a regenerative dryer is −40 °C (−40 °F); this means that when the air leaves the dryer there is as much water in the air as if the air had been "cooled" to −40 °C (−40 °F).

http://www.airmax.ca/PDFs/Serie12_ang.pdf