(b)  Compressor:

A compressor can be considered as a turbine operating in reverse. Fluid enters the compressor at a low pressure and emanates at a higher pressure. If the changes in the kinetic energy and potential energy are ignored, and the energy losses are negligible, then the first law for this flow process reduces to

(13.5)

In a compressor, is negative. Because the work is being done on the system, . The work done on the compressor per unit mass of the fluid is equal to the increase in enthalpy of the fluid. The compressors discharge the fluid with higher enthalpy, ie, with higher pressure and temperature.