Compressed air discharged from an air compressor is hot and loaded with water vapor. An after-cooler reduces the temperature of the compressed air, causing a substantial amount of the entrained moisture to condense. Each 20°F reduction in temperature causes approximately 50% of the entrained water vapor to condense. This moisture is then removed from the compressed air system with a separator and drain assembly.

In a typical compressed air system, an after-cooler and separator are installed before the compressed air dryer. A properly sized after-cooler significantly reduces the water load that would otherwise be placed on the compressed air dryer.



In Van Air AC series air-cooled after-coolers, hot compressed air is introduced to the core as ambient air is drawn across it, leaving the exiting air cooler. AC series after-coolers are normally sized for a 15°F (or less) approach to ambient air. For example, a compressor discharges 250°F air and the after-cooler is located in 80°F ambient conditions. With a 15°F approach, the air exiting the after-cooler will be 95°F and saturated, and the moisture created by cooling from 250°F to 95°F will condense.


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