Gas compression and compressors

From equation 6.12, the shaft work of compression W required to compress unit mass of gas from pressure P to pressure P2 in a reversible frictionless process, in which changes in potential and kinetic energy are negligible, is 

Although isothermal compression is desirable, in practice the heat of compression is never removed fast enough to make this possible. In actual compressors only a small fraction of the heat of compression is removed and the process is almost adiabatic. 

When ideal gases are compressed under reversible adiabatic conditions they obey equation 6.32, which can be written as 

Equation 6.89 gives the theoretical adiabatic work of compression from pressure P to pressure P2. 

Compression is often done in several stages with the gas being cooled 

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