A combined gas turbine-vapor power plant has a net power output of 15 MW. Air enters the compressor of the gas turbine at 100 kPa, 290 K and is compressed to 1100 kPa. The isentropic efficiency of the compressor is 80%. The conditions at the inlet to the turbine are 1100 kPa and 1400 K. Air expands through the turbine, that has an isentropic efficiency of 88%, to a pressure of 100 kPa. Air then passes through the interconnecting heat exchanger, and is finally discharged at 420 K. Steam enters the turbine of the vapor power cycle at 8 MPa, 390oC and expands to the condenser at a 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 rate of heat transfer to the combined cycle.
(b) The mass flow rates of Air
(c) The thermal efficiency (ηth) of the combined cycle