Refrigerant dryers are the most common used type of compressed air dryers. They consist of an air-to-air heat exchanger and an air-to-Freon heat exchanger. The compressed air from the compressor first passes the air-to-air heat exchanger. In this phase the incoming air is pre-cooled by the outgoing air and the outgoing air is heated. In the second phase the compressed air is passing the air- to-Freon heat exchanger, in this phase the compressed air is cooled further down to a temperature of around 3°C. At his temperature the moisture is condensed, the free water droplets are collected and removed, at this point the relative humidity of the compressed air still is at 100%. In the next step the compressed air is heated with the incoming air, the increase in temperature assures that the relative humidity of the outgoing air is dropping below 50%. Refrigerant dryers are used in compressed air systems to avoid free water and corrosion in the system, a relative humidity of below 50% is enough to achieve this. Refrigerant dryers are available in a water cooled and an air cooled variant.
