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Combined Bigte

This document contains 4 problems related to combined cycle power plants and Rankine cycle steam plants. The first problem involves determining the mass flow rate of steam, net power output, and thermal efficiency given information about the gas turbine and heat exchanger conditions. The second problem involves determining the mass flow rate ratio of air to steam, required heat input, and thermal efficiency given additional information about the steam cycle. The third problem involves determining the compressor work, turbine work, and thermal efficiency of an ideal gas turbine cycle with multiple compression and expansion stages. The fourth problem involves determining the maximum water mass flow rate and air exit temperature given constraints on a Rankine cycle steam plant operating with exhaust from a gas turbine.

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Jayvee Cabrera Retuerma
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126 views1 page

Combined Bigte

This document contains 4 problems related to combined cycle power plants and Rankine cycle steam plants. The first problem involves determining the mass flow rate of steam, net power output, and thermal efficiency given information about the gas turbine and heat exchanger conditions. The second problem involves determining the mass flow rate ratio of air to steam, required heat input, and thermal efficiency given additional information about the steam cycle. The third problem involves determining the compressor work, turbine work, and thermal efficiency of an ideal gas turbine cycle with multiple compression and expansion stages. The fourth problem involves determining the maximum water mass flow rate and air exit temperature given constraints on a Rankine cycle steam plant operating with exhaust from a gas turbine.

Uploaded by

Jayvee Cabrera Retuerma
Copyright
© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
Available Formats
Download as DOCX, PDF, TXT or read online on Scribd
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1.

The gas-turbine portion of a combined gas-steam power plant has a pressure ratio
of 16. Air enters the compressor at 300 K at a rate of 14 kg/s and is heated to
1500 K in the combustion chamber. The combustion gases leaving the gas turbine
are used to heat the steam to 400 C at 10 MPa in a heat exchanger. The combustion
gases leave the heat exchanger at 420 K. The steam leaving the turbine is
condensed at 15 kPa. Assuming all the compression and expansion processes to be
isentropic, determine (a) the mass flow rate of the steam (b) the net power
output, and (c) the thermal efficiency of the combined cycle. For air, assume
constant specific heats at room temperature. [1.275 kg/s, 7819 kW, 66.4 percent]
2. Consider a combined gas-steam power plant that has a net power output of 280 MW.
The pressure ratio of the gas turbine cycle is 11. Air enters the compressor at
300 K and the turbine at 1100 K. The combustion gases leaving the gas turbine
are used to heat the steam at 5 MPa to 350 C in a heat exchanger. The combustion
gases leave the heat exchanger at 420 K. An open feedwater heater incorporated
with the steam cycle operates at a pressure of 0.8 MPa. The condenser pressure
is 10 kPa. Assuming isentropic efficiencies of 100 percent for the pump, 82
percent for the compressor, and 86 percent for the gas and steam turbines,
determine (a) the mass flow rate ratio of air to steam, (b) the required rate
of heat input in the combustion chamber, and (c) the thermal efficiency of the
combined cycle.
3. Consider an ideal gas-turbine cycle with two stages of compression and two stages
of expansion. The pressure ratio across each compressor stage and each turbine
stage is 8:1. The pressure at the entrance to the first compressor is 14 lbf/in2,
the temperature entering each compressor is 70 F, and the temperature entering
each turbine is 2000 F. An ideal regenerator is also incorporated into the cycle.
Determine the compressor work, the turbine work, and the thermal efficiency of
the cycle.
4. A Rankine steam power plant should operate with a high pressure of 3 MPa and a
low pressure of 10 kPa, and the boiler exit temperature should be 500 C. The
available high temperature source is the exhaust of 175 kg/s air at 600 C from
a gas turbine. If the boiler operates as a counterflowing heat exchanger where
the temperature difference at the pinch point is 20 C, find the maximum water
mass flow rate possible and the air exit temperature.

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