An aftercooler is a heat exchanger for cooling the discharge of a compressor. May be air or water cooled. It is an effective means of removing moisture from the compressed air. The heat from the compressed air is transferred outward to the aluminum fins of the aftercooler. The flywheel creates an air flow that rushes past and cools the aluminum fins.
The use of an air after cooler is essential when compressors are not equipped with a built-in after cooler fitted with water separator when the temperature of compressed air exiting the compressor without after cooler is approx. 35°C above ambient temperature.The after cooler consists of an air-air heat exchanger using the ambient air as cooling medium. The compressed air drives the fan which propels the ambient air.
Types of Aftercooler
There are two basic types of aftercoolers:
Air Cooled Aftercooler
Air cooled aftercooler us the ambient air to cool the hot compressed air. They cool the hot compressed air leaving the compressor at a temperature of approximately 200 F to 300 F to the desired inlet temperature of an air dryer which is approximately 100 F to 120 F. 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.
Water Cooled Aftercooler
A water cooled aftercooler comes in different styles. The most common style for compressed air service is a Shell and Tube Heat Aftercooler. It provides efficient cooling by using water to cool the hot compressed air from an air compressor. The hot compressed passes through the aftercooler tubes and cooling water flows in the opposite direction through the aftercooler shell. This counter current flow provides the most effective method of reducing the temperature of the compressed air discharged from the compressor.
Functions of After Cooler
- Cool air discharged from air compressors via the heat exchanger.
- Reduce risk of fire.
- Reduce compressed air moisture level.
- Increase system capacity.
- Protect downstream equipment from excessive heat.
- Routinely inspect.
- Should be clean.
- Check approach temperature and pressure.
- Monitor water quality in water cooled after cooler.
- Check drain valve daily in air cooled after cooler.