Some users need low water content and low temperature compressed air. At this time, the cold dryer can no longer set up a pre -cooler. Because the cold air is not set up, the cold air is not recycled, and the heat load of the evaporator will increase a lot. In this case, not only the power of the big refrigeration compressor is required to compensate for energy, but it also needs to be calculated on other components (evaporator, condenser and throwing components) of the entire refrigeration system.