Answer Happy

7.29. 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
7.29. 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 (T.), 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 x 10-3 T/K. The steam flows into an adiabatic turbine and exhausts at a pressure of 25 kPa. If the turbine efficiency n is 72%, (a) What is Ws, the power output of the turbine? (b) What is the thermodynamic efficiency of the boiler/turbine combination? (c) Determine Sg for the boiler and for the turbine. (d) Express Wlost (boiler) and Wlost (turbine) as fractions of Wideall, the ideal work of the process.