Question

Consider a combined gas-steam power cycle. The topping cycle is a simple Brayton cycle that has a pressure ratio of 7. Air enters the compressor at 15 ºC at a rate of 10 kg/s and the gas turbine at 950 ºC. The bottoming cycle is a reheat Rankine cycle between the pressure limits of 6 MPa and 10 kPa. Steam is heated in a heat exchanger at a rate of 1.15 kg/s by the exhaust gases leaving the gas turbine, and the exhaust gases leave the same exchanger at 200 ºC. Steam leaves the high-pressure turbine at 1 MPa and is reheated to 400 ºC in the heat exchanger before it expands in the low-pressure turbine. Assuming 80 percent isentropic efficiency for all pumps and turbines,

1) determine the enthalpy of air at the compressor outlet .

2)determine the enthalpy of air at the Turbine outlet

3)determine the enthalpy of steam-water mixture at the low pressure turbine outlet

4)determine the moisture content at the exist of the low-pressure turbine.

5) determine the steam temperature at the inlet of the high-pressure. (hint: trial and error)

6)determine the net power output of the combined plant

7) determine the thermal efficiency of the combined plant.

Answer #1

Note -I have solved first four Parts of this question

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A gas turbine power plant operates on a Brayton cycles has a
pressure ratio of 7. Air enters the
compressor at 300 K. The energy in the form of heat is transferred
to the air in the amount of 950
kJ/kg. Using a variable specific heat for air and assuming the
compressor isentropic efficiency is
83 percent and turbine isentropic efficiency is 85 percent.
Determine the followings:
(i) The highest temperature in the cycle
(ii) The net work output, in...

A steam power plant runs on a reheat Rankine cycle. Steam enters
both the high and low pressure turbines at 500oC. The maximum and
minimum pressures of the cycle are 10 MPa and 10 kPa, respectively.
Steam leaves the condenser as a saturated liquid. The moisture
content of the steam at the exit of the low-pressure turbine is 4%
if the actual expansion process is adiabatic; 8.5% if the ideal
expansion process is isentropic. The isentropic efficiencies of the
high-pressure...

QUESTION 5
A steam power plant is designed to operate on a reheat Rankine
cycle to produce 115 MW
of a net power output. Due to metallurgical limitation, the
high-pressure turbine is limited to
operate at maximum pressure and temperature of 15 MPa and 650°C,
respectively. The lowpressure
turbine is to operate at maximum pressure and temperature of 3.5
MPa, and
500°C, respectively. Both high and low pressure turbines have
maximum isentropic
efficiency of 87 percent. The maximum reheat pressure...

A steam power plant is designed to operate on a reheat Rankine
cycle to produce 115 MW of a
net power output. Due to metallurgical limitation, the
high-pressure turbine is limited to operate
at maximum pressure and temperature of 15 MPa and 650°C,
respectively. The low-pressure
turbine is to operate at maximum pressure and temperature of 3.5
MPa, and 500°C,
respectively. Both high and low pressure turbines have maximum
isentropic efficiency of 87
percent. The maximum reheat pressure is limited...

In a steam power plant which has a net power output of 45 MW,
steam is supplied at 10 MPa and 500°C. The steam is reheated after
passing through high pressure turbine to its original temperature
at a pressure of 1 MPa. Then the steam expanded to condenser
pressure. The condenser pressure is 5 kPa. Show the cycle on a T-s
diagram with respect to saturation lines, and determine; (i) the
thermal efficiency of the cycle; and (ii) the mass...

the ideal air standard Brayton cycle consists of the following
processes:
1-2 isentropic compression through a pressur ratio rp
=p2/p1
2-3 heat addition at constant pressure untill the pressure is
p3
3-4 isentropic expansion to the initial pressure
4-1 heat rejection at constnt pressure
A- show that the cycle efficiency for this cycle is
B-Air enters compressor of a gas turbine at 100kpa and
250c.for a pressure ratio of 5 and a maximum temp of
8500c , determine the thermal...

Consider a cogeneration power plant that is modified with reheat
and that produces 3 MW of power and supplies 7 MW of process heat.
Steam enters the high pressure turbine at 8 MPa and 500 C and
expands to a pressure of 1 MPa. At this pressure, part of the steam
is extracted from the turbine and routed to the process heater,
while the remainder is reheated to 500 C and expanded in the low
pressure turbine to the condenser...

Consider a 210-MW steam power plant that operates on a simple
ideal Rankine cycle. Steam enters the turbine at 10 MPa and 500°C
and is cooled in the condenser at a pressure of 7.5 kPa.
a.)Determine the quality of the steam at the turbine exit. Use
steam tables.
b.)Determine the thermal efficiency of the cycle.
c.)Determine the mass flow rate of the steam

A steam power cycle can be characterized by the pressures
between which it operates. The turbine
provides the work out with a high pressure inlet and low pressure
outlet. The pump does the opposite,
namely increase the pressure from a low value to a high value. For
a power plant operating between 7
MPa and 15 kPa, determine the ratio of the work delivered by the
turbine to the work consumed by the
pump. Assume the cycle is completely reversible...

A steam power plant of 15 MW operates on the simple ideal
Rankine cycle such that the water leaves the condenser as a
saturated liquid at a pressure of 15 kPa. The pressure of the water
leaving the pump is 5.0 MPa, and the temperature of the steam
entering the turbine is 650 ºC. (a) Show the sketch and cycle on a
T-s diagram. Determine (b) the thermal efficiency of the cycle and
(c) the mass flow rate in kg/s....

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