Acombined-cycle power plant employs a gas-turbine system with a thermal efficiency of 38% and 200 mwt of combustion-produced heat. the gas-turbine discharge is directed into a heat recovery steam generator (hrsg). find: (i) the thermal efficiency and (ii) the net output power of the combined cycle plant for two cases: [12 pts] (a) no heat augmentation in the hrsg with a resulting steam-power cycle thermal efficiency of 20%, and (b) hrsg heat supplementation of 50 mwt, which raises the steam cycle thermal efficiency to 27%.

a) The thermal efficiency is 50.4% and the net output power is 100.8 MW.

b) The thermal efficiency is 49.2% and the net output power is 123 MW.

Explanation:

a) To find out the thermal efficiency, we must calculate how much of the thermal energy is converted to mechanic work:

We know that the gas turbine delivers 38% of the 200 MWt in power to the generator. The remaining 62% of the heat is left in the escape gas, of which the HRSG is able to recover another 20%:

Knowing the efficiency and the thermal power delivered, we calculate the output power:

b)Now, we calculate how much power is recovered, knowing that we add 50 MWt to the original 62% in the HSRG:

Finally, we calculate the efficiency, knowing that total thermal power added is 250 MWt (200 MWt in the gas turbine plus 50 MWt in the HRSG)

1

explanation:

answer:

a

explanation: