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What is the role of the pre-cooler of the freeze dryer?

Technical Knowledge 2015-12-26 21:54:21
In the freeze dryer, the pre-cooler is not only the refrigeration recovery device of the refrigeration system, but also the low-temperature air regenerator after dehydration. It is a major component of the freeze dryer and is a characteristic condition that distinguishes the freeze dryer from other refrigeration equipment.

In the pre-cooler, the same amount of cold and hot fluid (compressed air) is exchanged by the temperature difference of little difference, for two purposes:

1. Initially reduce the temperature and water content of the moist heat saturated intake air, to a certain extent, reduce the heat load of the evaporator, thereby reducing the energy consumption of the whole machine;

2. The temperature of the compressed air which is lower in temperature and saturated with moisture is recovered, thereby reducing the relative humidity when the compressed air is discharged, so that the gas pipeline does not rust due to the excessive relative humidity of the gas, and also The phenomenon of “hanging” outside the pipe due to the low temperature of the outer wall of the gas pipeline is avoided, and the workshop environment is improved.

The condensed water is attached to the outer wall of the heat exchange pipe to be discharged more easily. Therefore, the saturated compressed air with a higher temperature is usually arranged to go to the shell side of the precooler, and the dry cold air with a lower temperature is taken to the precooler tube.

The presence of the pre-cooler allows compressed air to flow through the passage in the freeze dryer to self-contain the system. The air system and the refrigerant system cross each other in the evaporator, so that the saturated compressed air entering the freeze dryer is subjected to two cooling and one temperature rising process, and the absolute water content (dew point) and relative humidity (%) are obtained at the exhaust port. Very dry and compressed air.

If the pre-cooler is not designed or the pre-cooler is not properly designed, the output is only the humid cold wind with low dew point and high relative humidity. Its function has no great application value in industry.

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