Page 21 - Compression Machinery for Oil and Gas

10 SECTION I Fundamentals of Compression

= Efficiency
1 = Suction
2 = Discharge
Pressure S1 2
P2
2isen
T1
P1
1
h1 h2 isen h2
Enthalpy
Enthalpy(2isen) – Enthalpy(1)
Efficiency =
Enthalpy(2) – Enthalpy(1)
FIG. 1.3 Pressure-enthalpy diagram for gas compression.

FIG. 1.4 Pressure enthalpy diagram for methane, with the path for actual and isentropic compres-
sion. The range where methane can be treated as an ideal gas (i.e., at low pressures, where enthalpy is
only dependent on temperature, but not on pressure) is highlighted. (From GPSA Handbook.)