In the process of refrigeration dryer, pressure gas is in function. 

Hot, moist compressed air, precooled by outgoing cold, dry air, in the air-to-air heat exchanger, enters the air-to-refrigerant heat exchanger cooling it to evaporating temperature of the refrigerant and condensing the entrained contaminates. 

The cyclone separator separates condensate from cold air discharging it though an automatic drain trap. Re-entering the air-to-air heat exchanger, the cold dry air is reheated by the incoming air to approx 100C below the incoming air temperature. 

The compressor delivers the hot high pressure gas via the liquid separator to the air-cooled condenser where the remaining refrigerant is condensed and collected in the receiver. The subcooled liquid expands to evaporating pressure in the expansion valve. Heat is withdrawn from process air by the refrigerant entering  the evaporator. Before entering the compressor  the vapourized refrigerant is separated  from droplets by the liquid separator. The cycle is continuously repeated. 

At a certain pressure point the dry compressed air is used for different application according the pressure required for the application.