What is the thermodynamic efficiency of the boiler/turbine combination?

Exhaust gas at 400°C and 1 bar from internal-combustion engines flows at the rate of

125 mol⋅s−1 into a waste-heat boiler where saturated steam is generated at a pressure

of 1200 kPa. Water enters the boiler at 20°C (Tσ), and the exhaust gases are cooled to

within 10°C of the steam temperature. The heat capacity of the exhaust gases is CP /R =

3.34 + 1.12 × 10−3 T/K. The steam flows into an adiabatic turbine and exhausts at a

pressure of 25 kPa. If the turbine efficiency η is 72%,

(a) What is W

∙

S, the power output of the turbine?

(b) What is the thermodynamic efficiency of the boiler/turbine combination?

(c) Determine S

∙

G for the boiler and for the turbine.

(d) Express W

∙

lost (boiler) and W

∙

lost (turbine) as fractions of ∣W

∙

ideal∣, the ideal work of

the process.