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

Chapter 7, Problem 7.29

(choose chapter or problem)

Exhaust gas at 400°C and 1 bar from internal-combustion engines flows at the rate of \(125 mol \cdot s^{−1}\) into a waste-heat boiler where saturated steam is generated at a pressure of 1200 kPa. Water enters the boiler at 20°C \((T_{σ})\), and the exhaust gases are cooled to within 10°C of the steam temperature. The heat capacity of the exhaust gases is \(C_{P} /R = 3.34 + 1.12 × 10^{−3} T/K\). 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 \(\dot W_{S}\), the power output of the turbine?

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

(c) Determine \(\dot S_{G}\) for the boiler and for the turbine.

(d) Express \(\dot W_{lost}\) (boiler) and W∙lost (turbine) as fractions of \(∣ \dot W_{ideal} ∣\), the ideal work of the process.

Text Transcription:

125 mol cdot s^−1

(T_σ)

C_P /R =3.34 + 1.12 × 10^−3 T/K

dot W_S

dot S_G

dot W_lost

|dot W_deal|