The gas turbine portion of a combined cycle has a pressure ratio of 8. Air enters the compressor at 300 K and the turbine at 1300 K. The isentropic efficiency of the compressor and the turbine is 80 % and 85 % respectively. After the turbine, the gas pressure is 1 bar. The exhaust gases leaving the gas turbine are used to produce steam at 400 °C and 70 bar in a heat exchanger. The exhaust gases leave the heat exchanger at 450 K. The steam leaving the turbine is condensed at 0.05 bar. In the gas turbine, the fluid can be assumed to be air with a constant specific heat of 1006 J/(kg·K) and κ = 1.4. The steam turbine and feedwater pump are assumed to be isentropic. Calculate: (a) The ratio between the steam and gas mass flow rates. (b) The thermal efficiency of the combined cycle.
The gas turbine portion of a combined cycle has a pressure ratio of 8. Air enters the compressor at 300 K and the turbine at 1300 K. The isentropic efficiency of the compressor and the turbine is 80 % and 85 % respectively. After the turbine, the gas pressure is 1 bar. The exhaust gases leaving the gas turbine are used to produce steam at 400 °C and 70 bar in a heat exchanger. The exhaust gases leave the heat exchanger at 450 K. The steam leaving the turbine is condensed at 0.05 bar. In the gas turbine, the fluid can be assumed to be air with a constant specific heat of 1006 J/(kg·K) and κ = 1.4. The steam turbine and feedwater pump are assumed to be isentropic. Calculate:
(a) The ratio between the steam and gas mass flow rates.
(b) The thermal efficiency of the combined cycle.
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