Answer: The main role of the precooler in the cold dryer is to "recover" the cold carried by the compressed air after being cooled by the evaporator (for most users, this part of the cold is "waste cold"), and use this part of the cold to cool the high-temperature compressed air carrying a large amount of water vapor. This reduces the heat load of the cold dryer refrigeration system and achieves the purpose of energy saving. On the other hand, the temperature of the low-temperature compressed air is recovered in the precooler, so that the outer wall of the exhaust pipe will not have the annoying phenomenon of hanging dew due to the low temperature. In addition, after the compressed air temperature rises. Reduce the relative humidity of the air in the pipeline (up to φ=5%~10%). According to the metal corrosion theory, when the relative humidity of the environment is lower than the critical point (φ=40%), the rust phenomenon of the metal pipe will stop. Therefore, the cold dryer is now equipped with a precooler.
Strictly speaking, the precooler is not a necessary component of the freeze dryer, but it plays a big role in the operation of the cold dryer. Some users need compressed air with low water content and low temperature. In this case, the dryer can be equipped with no precooler. Without the precooler, the cold air cannot be recycled and the heat load of the evaporator will increase a lot.
