If an adsorption dryer is installed downstream of a refrigeration dryer, the criteria changes. With this layout, pre-dried compressed air is fed to the adsorption dryer. The refrigeration dryer removes part of the moisture from the compressed air. As a rule, the pressure dewpoint at the outlet of the refrigeration dryer is between 2 - 5°C. The compressed air at the inlet to the adsorption dryer is no longer 100% saturated, typically 15 - 30%. Formula 10.4.8.1 is used for determining the relative humidity.
