Determine the enthalpy and entropy of the exhaust steam.

A turbine operates adiabatically with superheated steam entering at T1 and P1 with a

mass flow rate m

∙

. The exhaust pressure is P2 and the turbine efficiency is η. For one of

the following sets of operating conditions, determine the power output of the turbine

and the enthalpy and entropy of the exhaust steam.

(a) T1 = 450°C, P1 = 8000 kPa, m

∙

= 80 kg⋅s−1, P2 = 30 kPa, η = 0.80.

(b) T1 = 550°C, P1 = 9000 kPa, m

∙

= 90 kg⋅s−1, P2 = 20 kPa, η = 0.77.

(c) T1 = 600°C, P1 = 8600 kPa, m

∙

= 70 kg⋅s−1, P2 = 10 kPa, η = 0.82.

(d) T1 = 400°C, P1 = 7000 kPa, m

∙

= 65 kg⋅s−1, P2 = 50 kPa, η = 0.75.

(e) T1 = 200°C, P1 = 1400 kPa, m

∙

= 50 kg⋅s−1, P2 = 200 kPa, η = 0.75.

(f) T1 = 900(°F), P1 = 1100 (psia), m

∙

= 150(lbm)(s)−1, P2 = 2(psia), η = 0.80.

(g) T1 = 800(°F), P1 = 1000 (psia), m

∙

= 100(lbm)(s)−1, P2 = 4(psia), η = 0.75.

Solution: