Star Air Systems High Pressure Breathing Air Compressor After Coolers

Why is aftercooling important?

The compressed air discharged from an air compressor is hot. Compressed air at these temperatures contains large quantities of water in vapor form. As the compressed air cools this water vapor condenses into a liquid form. As an example if an aftercooler is not used, a 200 scfm compressor operating at 100 psig introduces 45 gallons of water into the compressed air system each day.

Air Cooled Aftercoolers

Air cooled aftercoolers use ambient air to cool the hot compressed air. The compressed air enters the air cooled aftercooler. The compressed air travels through either finned tubes or corrugated aluminum sheets of the aftercooler while ambient air is forced over the cooler by a motor-driven fan. The cooler, ambient air removes heat from the compressed air.

Water-Cooled Pipe Line Aftercooler

A water-cooled pipe line aftercooler comes in different styles. The most common style for compressed air service is a Shell and Tube Heat Exchanger/Aftercooler. The pipe line aftercooler consists of a shell with a bundle of tubes fitted inside. Typically the compressed air flows through the tubes in one direction as water flows on the shell side in the opposite direction. Heat from the compressed air is transferred to the water. Water vapor forms as the compressed air cools. The moisture is removed by the moisture separator and drain valve. A modulating valve is recommended to maintain a consistent temperature and reduce water consumption. The tube bundles can be fixed or removable. Fixed tube bundles cost less but are more difficult to maintain than bundles that can be removed for cleaning or service.

The disadvantages of a water-cooled aftercooler include high water usage and difficult heat recovery. Advantages to using a water-cooled aftercooler include better heat transfer and no required electricity.

An oversized aftercooler is usually cost-effective; it will produce cooler air with less moisture, reducing the requirements for the air dryer. Additionally, a larger aftercooler will have a lower pressure drop, lowering the necessary discharge pressure from the compressor. For the best results, size the aftercooler for a 1 to 2 psi pressure drop.

Star Air Systems - 4318 Comanche Trail
Greensboro, NC 27406
e-mail: starair@starairsystems.com

office:336-854-9015 FAX:336-510-6178

Your #1 Source for High Pressure Service for over 17 years!

We are one of the nations best high pressure compressor service facilities. We offer complete breathing systems with service, maintenance and air testing.

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