A gas-turbine plant operates on the regenerative Brayton cycle with two stages of reheating and two-stages of intercooling between the pressure limits of 100 and 1200 kPa. The working fluid is air. The air enters the first and the second stages of the compressor at 300 K and 350 K, respectively, and the first and the second stages of the turbine at 1400 K and 1300 K, respectively. Assuming both the compressor and the turbine have an isentropic efficiency of 80 percent and the regenerator has an effectiveness of 75 percent and using variable specific heats, determine
(a) the back work ratio and the net work output
(b) the thermal efficiency
(c) the secondlaw efficiency of the cycle. Also determine
(d) the exergies at the exits of the combustion chamber (state 6) and the regenerator(state 10) (See Fig. 9-43 in the text). (a) 0.523, 317 kJ/kg, (b) 0.553, (c) 0.704, (d) 931 kJ/kg, 129 kJ/kg