The Compressed air is used in many Industries for variety of applications. The atmospheric air contains lot of moisture . The compression of air involves a considerable rise in it’s temperature. It is necessary to cool this air which otherwise may lead to the following bad effects :

Increase in size of the pipe-line due to higher volume of air at high temperature.
Increase in HP required for compression in interstages.
Development of cracks in pipe-line in long run.
Corrossion of pipe-line & machine tools due to moist air.

It is common that the air is compressed in one or more stages. Inter Coolers are provided between the stages to keep the temperature of air within safe limits while coming out from the next stage. After Coolers are used to cool the air coming out from the last stage. Generally water is used as a cooling media in both of these, as here the heat transfer co-efficient is higher than that in case of an air to air cooling.

What is so special in the design of these Coolers ?
As the air used is moist and is required to be cooled near to atmospheric temperature, there is a partial condensation of moisture.This factor is to be thoroughly considered while calculating the heat load, film co-efficients and LMTD.