A combined cycle power plant consists of a gas turbine unit and steam turbine unit, exhaust from the gas turbine being supplied to the steam generator using the data below, neglecting the mass flow rate of fuel, feed pump work and all the pressure losses.

Calculate;

(a)The cycle efficiency for the gas turbine cycle

(b)The cycle efficiency for the steam turbine cycle if the heat supplied in the generator was supplied by external fuel supply

(c)The mass flow rate of air to the gas turbine and steam to the steam turbine

(d)The overall efficiency of the combined cycle

Data:

  Pressure ratio for the gas turbine = 8:1

  Inlet temperature to the compressor = 15^oC

  Max. cycle temperature for the gas turbine cycle = 800^oC

  Temperature of gases leaving the steam generator = 160^oC

  Steam conditions at entry to the turbine = 20 bar, 400^oC

  Condenser pressure = 0.05 bar

  Total power output of the plant = 50 MW

  ɳ_{ise. comp} = 0.8                           ɳ_{ise. Gas Turbine}  = 0.82

  ɳ_{ise. Steam Turbine} =  0.8                 C_P = 1.11 KJ/kg. K   ;   γ = 1.333   ;  W_P = 0

  For air   C_P = 1.005 KJ/kg. K   ;    γ = C_P / C_V = 1.4