Consider the combined gas-steam power cycle shown in attached Figure. The topping cycle is a gas- turbine cycle that has a pressure ratio of 12. Air enters the compressor at 300 K and the turbine at 1200 K. The isentropic efficiency of the compressor is 80 percent, and that of the gas turbine is 85 percent. The bottoming cycle is a simple ideal Rankine cycle operating between the pressure limits of 8 MPa and 50 kPa. Steam is heated in a heat exchanger by the exhaust gases to a temperature of 400°C. The exhaust gases leave the heat exchanger at 420 K. Determine (a) the ratio of the mass flow rates of the steam and the combustion gases, (b) the total network output per kilogram of combustion gases, (c) the thermal efficiency of the combined cycle, (d) the exergy destruction associated with the process in the condenser per kilogram of combustion gases, and (e) the entropy generation associated with the process in the combustion chamber. Use variable specific heat for ideal gas and assume a source temperature of 1500 K and a sink temperature of 295 K.
Consider the combined gas-steam power cycle shown in attached Figure. The topping cycle is a gas-
turbine cycle that has a pressure ratio of 12. Air enters the compressor at 300 K and the turbine at 1200
K. The isentropic efficiency of the compressor is 80 percent, and that of the gas turbine is 85 percent.
The bottoming cycle is a simple ideal Rankine cycle operating between the pressure limits of 8 MPa and
50 kPa. Steam is heated in a heat exchanger by the exhaust gases to a temperature of 400°C. The exhaust
gases leave the heat exchanger at 420 K. Determine (a) the ratio of the mass flow rates of the steam and
the combustion gases, (b) the total network output per kilogram of combustion gases, (c) the thermal
efficiency of the combined cycle, (d) the exergy destruction associated with the process in the condenser
per kilogram of combustion gases, and (e) the entropy generation associated with the process in the
combustion chamber.
Use variable specific heat for ideal gas and assume a source temperature of 1500 K and a sink
temperature of 295 K.
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