The thermal efficiency of the combined

Question

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 30 kg/s. Assuming all the compression and expansion processes to be isentropic, determine

(a) The mass flow rate of air in the gas-turbine cycle,

(b) The rate of total heat input, and

(c) The thermal efficiency of the combined cycle.

 

Answer 1

For the following mechanical problem, apply the concept of Thermodynamics and simplify each and every part of the question by illustrating your work. The gas-turbine cycle of the combined gas-steam power plant encompasses a pressure ratio of 8. Air enters compressor at 290 K and the turbine at 1400 K. The combustion gases depart the gas turbine are employed to heat the steam at 15 MPa to 450°C in the heat exchanger. The combustion gases depart the heat exchanger at 247°C. Steam enlarges in a high-pressure turbine to a pressure of 3 MPa and is re-heated in the combustion chamber to 500°C prior to it expands in the low-pressure turbine to 10 kPa. The mass flow rate of steam is 30 kg/s. Supposing all the compression and expansion methods to be isentropic, find out: 1) The mass flow rate of air in the gas-turbine cycle 2) The rate of net heat input 3) The thermal effectiveness of combined cycle