In a refrigerated dryer, the precooler and the evaporator are two key components that work together to remove moisture from compressed air.

The precooler is the first stage in the air drying process. It receives the hot and moisture-laden compressed air from the compressor and cools it down. The precooler typically uses ambient air or a separate refrigerant circuit to cool the compressed air. By reducing the temperature of the air, the precooler causes a portion of the moisture vapor to condense into liquid water, which can then be separated and removed from the air stream.

Once the air has been pre-cooled and the condensed water has been separated, it enters the evaporator. The evaporator is the primary cooling stage in the refrigerated dryer. It further cools the air by utilizing a refrigeration system. The air is passed through the evaporator where it comes into contact with the cold refrigerant. As the air temperature drops, more moisture condenses, resulting in additional water separation. The condensed water is collected and drained from the system.

Overall, the precooler and evaporator work in tandem to lower the temperature of the compressed air, allowing moisture to condense and be removed. The precooler provides initial cooling, while the evaporator performs further cooling and moisture separation, resulting in dryer and moisture-free compressed air.