Refrigeration dryers work by cooling compressed air, reducing its water vapour holding ability. Compressed air leaving compressor is always fully saturated with water, it’s relative humidity is 100%. The maximum water amount held in air is highly dependent on temperature, therefore cooling results precipitating water in liquid phase. Fridge dryers of Parker domnick hunter are greatly cost effective. For economical reason they are re-heating the cooled air in a heat exchanger, resulting in lower inlet air temperature and energy savings.