The gas-turbine cycle of a combined gas–steam power plant has a pressure ratio of 8. air enters the compressor at 290 k and the turbine at 1400 k. the combustion gases leaving the gas turbine are used to heat the steam at 15 mpa to 450°c in a heat exchanger. the combustion gases leave the heat exchanger at 247°c. steam expands in a high-pressure turbine to a pressure of 3 mpa and is reheated in the combustion chamber to 500°c before it expands in a low-pressure turbine to 10 kpa. the mass flow rate of steam is 12 kg/s. assume isentropic efficiencies of 100 percent for the pump, 85 percent for the compressor, and 90 percent for the gas and steam turbines.

a.) determine the mass flow rate of air in the gas-turbine cycle. use steam tables and the table containing the ideal-gas properties of air.

the mass flow rate of air in the gas-turbine cycle is /s

b.) determine the rate of total heat input.

the rate of total heat input is .

c.) determine the thermal efficiency of the combined cycle

the thermal efficiency of the combined cycle is %.