Other Gas Power System Applications A combined gas

Chapter 9, Problem 96P

(choose chapter or problem)

A combined gas turbine–vapor power plant (Fig. 9.22) has a net power output of 100 MW. Air enters the compressor of the gas turbine at 100 kPa, 300 K, and is compressed to 1200 kPa. The isentropic efficiency of the compressor is 84%. The conditions at the inlet to the turbine are 1200 kPa and 1400 K. Air expands through the turbine, which has an isentropic efficiency of 88%, to a pressure of 100 kPa. The air then passes through the interconnecting heat exchanger, and is finally discharged at 480 K. Steam enters the turbine of the vapor power cycle at 8 MPa, \(400^{\circ} \mathrm{C}\), and expands to the condenser pressure of 8 kPa. Water enters the pump as saturated liquid at 8 kPa. The turbine and pump have isentropic efficiencies of 90 and 80%, respectively. Determine

(a) the mass flow rates of air and steam, each in kg/s.

(b) the thermal efficiency of the combined cycle.

(c) a full accounting of the net exergy increase of the air passing through the combustor of the gas turbine, \(\dot{m}_{\mathrm{air}}\left[\mathrm{e}_{\mathrm{f} 3}-\mathrm{e}_{\mathrm{f} 2}\right]\), in MW.

Discuss. Let \(T_{0}=300 \mathrm{\ K}, \ p_{0}=100\) kPa.