These dryers derive their cooling from a closed cycle refrigeration system based around one of three commercial refrigerants, R-22, R-134a or R410a. The refrigeration system these dryers use is similar to home and commercial air conditioning systems. The schematic shown to the right illustrates a typical Freon-based refrigerated compressed air dryer.
Freon-based refrigerated compressed air dryers generally consist of a heat exchanger that is similar to a water cooled after cooler. Instead of using water as the coolant, liquid CFC fills the shell of the heat exchanger. The liquid CFC is maintained at a pressure that allows it to boil at 3 °C (38 °F). After the CFC boils, the vapor is drawn through the suction line into a compressor, which compresses the CFC to a high pressure and high temperature. The high pressure/temperature CFC is cooled in the condenser and relaxes into its liquid state. The liquid is reintroduced into the heat exchanger via the metering device and a closed refrigeration cycle is formed. When the compressed air passes through the heat exchanger, it is cooled to the temperature of the boiling CFC. As the compressed air is cooled, it loses its ability to retain moisture and the water vapor condenses onto the inside of the exchanger tube.