Example
Steam enters an adiabatic turbine at 5 MPa and 450?C and leaves at a pressure of 1.4 MPa. Determine the work output of the turbine per unit mass flowing through the turbine if we can assume the process is reversible and neglect all changes of KE and PE.
Wout = m(h1-h2), Wout/m = h1-h2
state 1: P1=5 MPa, T1=450?C, from table A-6
h1=3316.2(kJ/kg), s1=6.819(kJ/kg K)
State 2: P2=1.4 MPa, s2=s1=6.819>sg=6.469 @ 1.4 MPa(table A-5),
state 2 is superheated: from table A-6 through interpolation
h2=2927.2+[(3040.4-2927.2)/(6.9534-6.7467)](6.819-6.7467)=2966.8 (kJ/kg). Wout/m = h1-h2 = 349.4 (kJ/kg)