A multistage compressor compresses gas or air over a series of stages. Each stage increases the pressure by a certain amount till the final required pressure is reached.
When the gas is compressed, heat is produced. This heat causes an increase in the volume. The pressure thus obtained will be higher than the actual pressure due to the temperature increase. Heat in the compressor can also damage the components of the cylinder, such as, the gaskets, o rings, etc.
This heat, therefore, has to be removed. The intercooler is a cooling device which removes the heat as the gas passes from one stage to the next.
The intercooler consists of tubes which are cooled by a cooling medium, usually water. As the gas passes through the tubes, it gets cooled.
Perfect or Complete Intercooling
If the temperature of the gas leaving the intercooler is equal to the room temperature, the cooling is said to be perfect. This is known as perfect intercooling or complete intercooling
Imperfect or Incomplete Intercooling
If the temperature of the gas leaving the intercooler is greater than the room temperature, the cooling is said to be imperfect. This is known as imperfect or incomplete intercooling.