10–1C Why is excessive moisture in steam undesirable in steam turbines? What is the highest moisture content allowed?
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10–2C Why is the Carnot cycle not a realistic model for steam power plants?
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10–3E
Water enters the boiler of a steady-flow Carnot engine as a saturated
liquid at 180 psia and leaves with a quality of 0.90. Steam leaves the
turbine at a pressure of 14.7 psia. Show the cycle on a T-s diagram
relative to the saturation lines, and determine (a) the thermal
efficiency, (b) the quality at the end of the isothermal heat-rejection
process, and (c) the net work output. Answers: (a) 19.3 percent, (b)
0.153, (c) 148 Btu/lbm
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10–4
A steady-flow Carnot cycle uses water as the working fluid. Water
changes from saturated liquid to saturated vapor as heat is transferred
to it from a source at 250°C. Heat rejection takes place at a pressure
of 20 kPa. Show the cycle on a T-s diagram relative to the saturation
lines, and determine (a) the thermal efficiency, (b) the amount of heat
rejected, in kJ/kg, and (c) the net work output.
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10–5 Repeat Prob. 10–4 for a heat rejection pressure of 10 kPa.
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10–6
Consider a steady-flow Carnot cycle with water as the working fluid.
The maximum and minimum temperatures in the cycle are 350 and 60°C. The
quality of water is 0.891 at the beginning of the heat-rejection process
and 0.1 at the end. Show the cycle on a T-s diagram relative to the
saturation lines, and determine (a) the thermal efficiency, (b) the
pressure at the turbine inlet, and (c) the net work output. Answers: (a)
0.465, (b) 1.40 MPa, (c) 1623 kJ/kg The Simple Rankine Cycle
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10–7C What four processes make up the simple ideal Rankine cycle?
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10–8C
Consider a simple ideal Rankine cycle with fixed turbine inlet
conditions. What is the effect of lowering the condenser pressure on
Pump work input: (a) increases, (b) decreases, (c) remains the same
Turbine work (a) increases, (b) decreases, output: (c) remains the same
Heat supplied: (a) increases, (b) decreases, (c) remains the same
Heat rejected: (a) increases, (b) decreases, (c) remains the same
Cycle efficiency: (a) increases, (b) decreases, (c) remains the same
Moisture content (a) increases, (b) decreases, at turbine exit: (c)
remains the same
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10–9C
Consider a simple ideal Rankine cycle with fixed turbine inlet
temperature and condenser pressure. What is the effect of increasing the
boiler pressure on
Pump work input: (a) increases, (b) decreases, (c) remains the same
Turbine work (a) increases, (b) decreases, output: (c) remains the same
Heat supplied: (a) increases, (b) decreases, (c) remains the same
Heat rejected: (a) increases, (b) decreases, (c) remains the same
Cycle efficiency: (a) increases, (b) decreases, (c) remains the same
Moisture content (a) increases, (b) decreases, at turbine exit: (c)
remains the same
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10–10C
Consider a simple ideal Rankine cycle with fixed boiler and condenser
pressures. What is the effect of superheating the steam to a higher
temperature on
Pump work input: (a) increases, (b) decreases, (c) remains the same
Turbine work (a) increases, (b) decreases, output: (c) remains the same
Heat supplied: (a) increases, (b) decreases, (c) remains the same
Heat rejected: (a) increases, (b) decreases, (c) remains the same
Cycle efficiency: (a) increases, (b) decreases, (c) remains the same
Moisture content (a) increases, (b) decreases, at turbine exit: (c)
remains the same
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10–11C How do actual vapor power cycles differ from idealized ones?
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10–12C Compare the pressures at the inlet and the exit of the boiler for (a) actual and (b) ideal cycles.
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10–13C
The entropy of steam increases in actual steam turbines as a result of
irreversibilities. In an effort to control entropy increase, it is
proposed to cool the steam in the turbine by running cooling water
around the turbine casing. It is argued that this will reduce the
entropy and the enthalpy of the steam at the turbine exit and thus
increase the work output. How would you evaluate this proposal?
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10–14C Is it possible to maintain a pressure of 10 kPa in a condenser that is being cooled by river water entering at 20°C?
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10–15
A steam power plant operates on a simple ideal Rankine cycle between
the pressure limits of 3 MPa and 50 kPa. The temperature of the steam at
the turbine inlet is 300°C, and the mass flow rate of steam through the
cycle is 35 kg/s. Show the cycle on a T-s diagram with respect to
saturation lines, and determine (a) the thermal efficiency of the cycle
and (b) the net power output of the power plant.
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10–16
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 10 kPa. Show the cycle on a T-s
diagram with respect to saturation lines, and determine (a) the quality
of the steam at the turbine exit, (b) the thermal efficiency of the
cycle, and (c) the mass flow rate of the steam.
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10–17
Repeat Prob. 10–16 assuming an isentropic efficiency of 85 percent for
both the turbine and the pump. Answers: (a) 0.874, (b) 34.1 percent, (c)
194 kg/s
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10–18E
A steam power plant operates on a simple ideal Rankine cycle between
the pressure limits of 1250 and 2 psia. The mass flow rate of steam
through the cycle is 75 lbm/s. The moisture content of the steam at the
turbine exit is not to exceed 10 percent. Show the cycle on a T-s
diagram with respect to saturation lines, and determine (a) the minimum
turbine inlet temperature, (b) the rate of heat input in the boiler, and
(c) the thermal efficiency of the cycle.
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10–19E Repeat Prob. 10–18E assuming an isentropic efficiency of 85 percent for both the turbine and the pump.
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10–20
Consider a coal-fired steam power plant that produces 300 MW of
electric power. The power plant operates on a simple ideal Rankine cycle
with turbine inlet conditions of 5 MPa and 450°C and a condenser
pressure of 25 kPa. The coal has a heating value (energy released when
the fuel is burned) of 29,300 kJ/kg. Assuming that 75 percent of this
energy is transferred to the steam in the boiler and that the electric
generator has an efficiency of 96 percent, determine (a) the overall
plant efficiency (the ratio of net electric power output to the energy
input as fuel) and (b) the required rate of coal supply.
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10–21
Consider a solar-pond power plant that operates on a simple ideal
Rankine cycle with refrigerant-134a as the working fluid. The
refrigerant enters the turbine as a saturated vapor at 1.4 MPa and
leaves at 0.7 MPa. The mass flow rate of the refrigerant is 3 kg/s. Show
the cycle on a T-s diagram with respect to saturation lines, and
determine (a) the thermal efficiency of the cycle and (b) the power
output of this plant.
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10–22
Consider a steam power plant that operates on a simple ideal Rankine
cycle and has a net power output of 45 MW. Steam enters the turbine at 7
MPa and 500°C and is cooled in the condenser at a pressure of 10 kPa by
running cooling water from a lake through the tubes of the condenser at
a rate of 2000 kg/s. Show the cycle on a T-s diagram with respect to
saturation lines, and determine (a) the thermal efficiency of the cycle,
(b) the mass flow rate of the steam, and (c) the temperature rise of
the cooling water. Answers: (a) 38.9 percent, (b) 36 kg/s, (c) 8.4°C
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10–23
Repeat Prob. 10–22 assuming an isentropic efficiency of 87 percent for
both the turbine and the pump. Answers: (a) 33.8 percent, (b) 41.4 kg/s,
(c) 10.5°C
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10–24
The net work output and the thermal efficiency for the Carnot and the
simple ideal Rankine cycles with steam as the working fluid are to be
calculated and compared. Steam enters the turbine in both cases at 10
MPa as a saturated vapor, and the condenser pressure is 20 kPa. In the
Rankine cycle, the condenser exit state is saturated liquid and in the
Carnot cycle, the boiler inlet state is saturated liquid. Draw the T-s
diagrams for both cycles.
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10–25
A binary geothermal power plant uses geothermal water at 160°C as the
heat source. The cycle operates on the simple Rankine cycle with
isobutane as the working fluid. Heat is transferred to the cycle by a
heat exchanger in which geothermal liquid water enters at 160°C at a
rate of 555.9 kg/s and leaves at 90°C. Isobutane enters the turbine at
3.25 MPa and 147°C at a rate of 305.6 kg/s, and leaves at 79.5°C and 410
kPa. Isobutane is condensed in an air-cooled condenser and pumped to
the heat exchanger pressure. Assuming the pump to have an isentropic
efficiency of 90 percent, determine (a) the isentropic efficiency of the
turbine, (b) the net power output of the plant, and (c) the thermal
efficiency of the cycle.
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10–26
The schematic of a single-flash geothermal power plant with state
numbers is given in Fig. P10–26. Geothermal resource exists as saturated
liquid at 230°C. The geothermal liquid is withdrawn from the production
well at a rate of 230 kg/s, and is flashed to a pressure of 500 kPa by
an essentially isenthalpic flashing process where the resulting vapor is
separated from the liquid in a separator and directed to the turbine.
The steam leaves the turbine at 10 kPa with a moisture content of 10
percent and enters the condenser where it is condensed and routed to a
reinjection well along with the liquid coming off the separator.
Determine (a) the mass flow rate of steam through the turbine, (b) the
isentropic efficiency of the turbine, (c) the power output of the
turbine, and (d) the thermal efficiency of the plant (the ratio of the
turbine work output to the energy of the geothermal fluid relative to
standard ambient conditions).
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10–27
Reconsider Prob. 10–26. Now, it is proposed that the liquid water
coming out of the separator be routed through another flash chamber
maintained at 150 kPa, and the steam produced be directed to a lower
stage of the same turbine. Both streams of steam leave the turbine at
the same state of 10 kPa and 90 percent quality. Determine (a) the
temperature of steam at the outlet of the second flash chamber, (b) the
power produced by the lower stage of the turbine, and (c) the thermal
efficiency of the plant.
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10–28
Reconsider Prob. 10–26. Now, it is proposed that the liquid water
coming out of the separator be used as the heat source in a binary cycle
with isobutane as the working fluid. Geothermal liquid water leaves the
heat exchanger at 90°C while isobutane enters the turbine at 3.25 MPa
and 145°C and leaves at 80°C and 400 kPa. Isobutane is condensed in an
air-cooled condenser and then pumped to the heat exchanger pressure.
Assuming an isentropic efficiency of 90 percent for the pump, determine
(a) the mass flow rate of isobutane in the binary cycle, (b) the net
power outputs of both the flashing and the binary sections of the plant,
and (c) the thermal efficiencies of the binary cycle and the combined
plant
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10–29C
How do the following quantities change when a simple ideal Rankine
cycle is modified with reheating? Assume the mass flow rate is
maintained the same.
Pump work input: (a) increases, (b) decreases, (c) remains the same
Turbine work (a) increases, (b) decreases, output: (c) remains the same
Heat supplied: (a) increases, (b) decreases, (c) remains the same
Heat rejected: (a) increases, (b) decreases, (c) remains the same
Moisture content (a) increases, (b) decreases, at turbine exit: (c)
remains the same
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10–30C
Show the ideal Rankine cycle with three stages of reheating on a T-s
diagram. Assume the turbine inlet temperature is the same for all
stages. How does the cycle efficiency vary with the number of reheat
stages?
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10–31C
Consider a simple Rankine cycle and an ideal Rankine cycle with three
reheat stages. Both cycles operate between the same pressure limits. The
maximum temperature is 700°C in the simple cycle and 450°C in the
reheat cycle. Which cycle do you think will have a higher thermal
efficiency?
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10–32
A steam power plant operates on the ideal reheat Rankine cycle. Steam
enters the highpressure turbine at 8 MPa and 500°C and leaves at 3 MPa.
Steam is then reheated at constant pressure to 500°C before it expands
to 20 kPa in the low-pressure turbine. Determine the turbine work
output, in kJ/kg, and the thermal efficiency of the cycle. Also, show
the cycle on a T-s diagram with respect to saturation lines.
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10–33
Reconsider Prob. 10–32. Using EES (or other) software, solve this
problem by the diagram window data entry feature of EES. Include the
effects of the turbine and pump efficiencies and also show the effects
of reheat on the steam quality at the low-pressure turbine exit. Plot
the cycle on a T-s diagram with respect to the saturation lines. Discuss
the results of your parametric studies.
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10–34
Consider a steam power plant that operates on a reheat Rankine cycle
and has a net power output of 80 MW. Steam enters the high-pressure
turbine at 10 MPa and 500°C and the low-pressure turbine at 1 MPa and
500°C. Steam leaves the condenser as a saturated liquid at a pressure of
10 kPa. The isentropic efficiency of the turbine is 80 percent, and
that of the pump is 95 percent. Show the cycle on a T-s diagram with
respect to saturation lines, and determine (a) the quality (or
temperature, if superheated) of the steam at the turbine exit, (b) the
thermal efficiency of the cycle, and (c) the mass flow rate of the
steam.
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10–35
Repeat Prob. 10–34 assuming both the pump and the turbine are
isentropic. Answers: (a) 0.949, (b) 41.3 percent, (c) 50.0 kg/s
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10–36E
Steam enters the high-pressure turbine of a steam power plant that
operates on the ideal reheat Rankine cycle at 800 psia and 900°F and
leaves as saturated vapor. Steam is then reheated to 800°F before it
expands to a pressure of 1 psia. Heat is transferred to the steam in the
boiler at a rate of 6 x 104 Btu/s. Steam is cooled in the condenser by
the cooling water from a nearby river, which enters the condenser at
45°F. Show the cycle on a T-s diagram with respect to saturation lines,
and determine (a) the pressure at which reheating takes place, (b) the
net power output and thermal efficiency, and (c) the minimum mass flow
rate of the cooling water required.
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10–37
A steam power plant operates on an ideal reheat Rankine cycle between
the pressure limits of 15 MPa and 10 kPa. The mass flow rate of steam
through the cycle is 12 kg/s. Steam enters both stages of the turbine at
500°C. If the moisture content of the steam at the exit of the
low-pressure turbine is not to exceed 10 percent, determine (a) the
pressure at which reheating takes place, (b) the total rate of heat
input in the boiler, and (c) the thermal efficiency of the cycle. Also,
show the cycle on a T-s diagram with respect to saturation lines.
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10–38
A steam power plant operates on the reheat Rankine cycle. Steam enters
the high-pressure turbine at 12.5 MPa and 550°C at a rate of 7.7 kg/s
and leaves at 2 MPa. Steam is then reheated at constant pressure to
450°C before it expands in the low-pressure turbine. The isentropic
efficiencies of the turbine and the pump are 85 percent and 90 percent,
respectively. Steam leaves the condenser as a saturated liquid. If the
moisture content of the steam at the exit of the turbine is not to
exceed 5 percent, determine (a) the condenser pressure, (b) the net
power output, and (c) the thermal efficiency
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10–39C
How do the following quantities change when the simple ideal Rankine
cycle is modified with regeneration? Assume the mass flow rate through
the boiler is the same.
Turbine work (a) increases, (b) decreases, output: (c) remains the same
Heat supplied: (a) increases, (b) decreases, (c) remains the same
Heat rejected: (a) increases, (b) decreases, (c) remains the same
Moisture content (a) increases, (b) decreases, at turbine exit: (c)
remains the same
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10–40C
During a regeneration process, some steam is extracted from the turbine
and is used to heat the liquid water leaving the pump. This does not
seem like a smart thing to do since the extracted steam could produce
some more work in the turbine. How do you justify this action?
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10–41C How do open feedwater heaters differ from closed feedwater heaters?
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10–42C
Consider a simple ideal Rankine cycle and an ideal regenerative Rankine
cycle with one open feedwater heater. The two cycles are very much
alike, except the feedwater in the regenerative cycle is heated by
extracting some steam just before it enters the turbine. How would you
compare the efficiencies of these two cycles?
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10–43C
Devise an ideal regenerative Rankine cycle that has the same thermal
efficiency as the Carnot cycle. Show the cycle on a T-s diagram.
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10–44
A steam power plant operates on an ideal regenerative Rankine cycle.
Steam enters the turbine at 6 MPa and 450°C and is condensed in the
condenser at 20 kPa. Steam is extracted from the turbine at 0.4 MPa to
heat the feedwater in an open feedwater heater. Water leaves the
feedwater heater as a saturated liquid. Show the cycle on a T-s diagram,
and determine (a) the net work output per kilogram of steam flowing
through the boiler and (b) the thermal efficiency of the cycle. Answers:
(a) 1017 kJ/kg, (b) 37.8 percent
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10–45
Repeat Prob. 10–44 by replacing the open feedwater heater with a closed
feedwater heater. Assume that the feedwater leaves the heater at the
condensation temperature of the extracted steam and that the extracted
steam leaves the heater as a saturated liquid and is pumped to the line
carrying the feedwater.
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10–46
A steam power plant operates on an ideal regenerative Rankine cycle
with two open feedwater heaters. Steam enters the turbine at 10 MPa and
600°C and exhausts to the condenser at 5 kPa. Steam is extracted from
the turbine at 0.6 and 0.2 MPa. Water leaves both feedwater heaters as a
saturated liquid. The mass flow rate of steam through the boiler is 22
kg/s. Show the cycle on a T-s diagram, and determine (a) the net power
output of the power plant and (b) the thermal efficiency of the cycle.
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10–47
Consider an ideal steam regenerative Rankine cycle with two feedwater
heaters, one closed and one open. Steam enters the turbine at 12.5 MPa
and 550°C and exhausts to the condenser at 10 kPa. Steam is extracted
from the turbine at 0.8 MPa for the closed feedwater heater and at 0.3
MPa for the open one. The feedwater is heated to the condensation
temperature of the extracted steam in the closed feedwater heater. The
extracted steam leaves the closed feedwater heater as a saturated
liquid, which is subsequently throttled to the open feedwater heater.
Show the cycle on a T-s diagram with respect to saturation lines, and
determine (a) the mass flow rate of steam through the boiler for a net
power output of 250 MW and (b) the thermal efficiency of the cycle.
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10–48
Reconsider Prob. 10–47. Using EES (or other) software, investigate the
effects of turbine and pump efficiencies as they are varied from 70
percent to 100 percent on the mass flow rate and thermal efficiency.
Plot the mass flow rate and the thermal efficiency as a function of
turbine efficiency for pump efficiencies of 70, 85, and 100 percent, and
discuss the results. Also plot the T-s diagram for turbine and pump
efficiencies of 85 percent.
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10–49
A steam power plant operates on an ideal reheat– regenerative Rankine
cycle and has a net power output of 80 MW. Steam enters the
high-pressure turbine at 10 MPa and 550°C and leaves at 0.8 MPa. Some
steam is extracted at this pressure to heat the feedwater in an open
feedwater heater. The rest of the steam is reheated to 500°C and is
expanded in the low-pressure turbine to the condenser pressure of 10
kPa. Show the cycle on a T-s diagram with respect to saturation lines,
and determine (a) the mass flow rate of steam through the boiler and (b)
the thermal efficiency of the cycle. Answers: (a) 54.5 kg/s, (b) 44.4
percent
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10–50
Repeat Prob. 10–49, but replace the open feedwater heater with a closed
feedwater heater. Assume that the feed water leaves the heater at the
condensation temperature of the extracted steam and that the extracted
steam leaves the heater as a saturated liquid and is pumped to the line
carrying the feedwater.
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10–51E
A steam power plant operates on an ideal reheat–regenerative Rankine
cycle with one reheater and two open feedwater heaters. Steam enters the
high-pressure turbine at 1500 psia and 1100°F and leaves the
low-pressure turbine at 1 psia. Steam is extracted from the turbine at
250 and 40 psia, and it is reheated to 1000°F at a pressure of 140 psia.
Water leaves both feedwater heaters as a saturated liquid. Heat is
transferred to the steam in the boiler at a rate of 4 105 Btu/s. Show
the cycle on a T-s diagram with respect to saturation lines, and
determine (a) the mass flow rate of steam through the boiler, (b) the
net power output of the plant, and (c) the thermal efficiency of the
cycle.
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10–52
A steam power plant operates on the reheatregenerative Rankine cycle
with a closed feedwater heater. Steam enters the turbine at 12.5 MPa and
550°C at a rate of 24 kg/s and is condensed in the condenser at a
pressure of 20 kPa. Steam is reheated at 5 MPa to 550°C. Some steam is
extracted from the low-pressure turbine at 1.0 MPa, is completely
condensed in the closed feedwater heater, and pumped to 12.5 MPa before
it mixes with the feedwater at the same pressure. Assuming an isentropic
efficiency of 88 percent for both the turbine and the pump, determine
(a) the temperature of the steam at the inlet of the closed feedwater
heater, (b) the mass flow rate of the steam extracted from the turbine
for the closed feedwater heater, (c) the net power output, and (d) the
thermal efficiency.
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10–53C How can the second-law efficiency of a simple ideal Rankine cycle be improved?
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10–54
Determine the exergy destruction associated with each of the processes
of the Rankine cycle described in Prob. 10–15, assuming a source
temperature of 1500 K and a sink temperature of 290 K.
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10–55
Determine the exergy destruction associated with each of the processes
of the Rankine cycle described in Prob. 10–16, assuming a source
temperature of 1500 K and a sink temperature of 290 K.
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10–56
Determine the exergy destruction associated with the heat rejection
process in Prob. 10–22. Assume a source temperature of 1500 K and a sink
temperature of 290 K. Also, determine the exergy of the steam at the
boiler exit. Take P0 = 100 kPa.
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10–57
Determine the exergy destruction associated with each of the processes
of the reheat Rankine cycle described in Prob. 10–32. Assume a source
temperature of 1800 K and a sink temperature of 300 K.
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10–58
Reconsider Prob. 10–57. Using EES (or other) software, solve this
problem by the diagram window data entry feature of EES. Include the
effects of the turbine and pump efficiencies to evaluate the
irreversibilities associated with each of the processes. Plot the cycle
on a T-s diagram with respect to the saturation lines. Discuss the
results of your parametric studies.
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10–59
Determine the exergy destruction associated with the heat addition
process and the expansion process in Prob. 10–34. Assume a source
temperature of 1600 K and a sink temperature of 285 K. Also, determine
the exergy of the steam at the boiler exit. Take P0 = 100 kPa. Answers:
1289 kJ/kg, 247.9 kJ/kg, 1495 kJ/kg
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10–60
Determine the exergy destruction associated with the regenerative cycle
described in Prob. 10–44. Assume a source temperature of 1500 K and a
sink temperature of 290 K.
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10–61
Determine the exergy destruction associated with the reheating and
regeneration processes described in Prob. 10–49. Assume a source
temperature of 1800 K and a sink temperature of 290 K.
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10–62
The schematic of a single-flash geothermal power plant with state
numbers is given in Fig. P10–62. Geothermal resource exists as saturated
liquid at 230°C. The geothermal liquid is withdrawn from the production
well at a rate of 230 kg/s and is flashed to a pressure of 500 kPa by
an essentially isenthalpic flashing process where the resulting vapor is
separated from the liquid in a separator and is directed to the
turbine. The steam leaves the turbine at 10 kPa with a moisture content
of 5 percent and enters the condenser where it is condensed; it is
routed to a reinjection well along with the liquid coming off the
separator. Determine (a) the power output of the turbine and the thermal
efficiency of the plant, (b) the exergy of the geothermal liquid at the
exit of the flash chamber, and the exergy destructions and the
second-law (exergetic) efficiencies for (c) the flash chamber, (d) the
turbine, and (e) the entire plant.
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10–63C
How is the utilization factor Pu for cogeneration plants defined? Could
Pu be unity for a cogeneration plant that does not produce any power?
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10–64C
Consider a cogeneration plant for which the utilization factor is 1. Is
the irreversibility associated with this cycle necessarily zero?
Explain.
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10–65C
Consider a cogeneration plant for which the utilization factor is 0.5.
Can the exergy destruction associated with this plant be zero? If yes,
under what conditions?
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10–66C What is the difference between cogeneration and regeneration?
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10–67
Steam enters the turbine of a cogeneration plant at 7 MPa and 500°C.
One-fourth of the steam is extracted from the turbine at 600-kPa
pressure for process heating. The remaining steam continues to expand to
10 kPa. The extracted steam is then condensed and mixed with feedwater
at constant pressure and the mixture is pumped to the boiler pressure of
7 MPa. The mass flow rate of steam through the boiler is 30 kg/s.
Disregarding any pressure drops and heat losses in the piping, and
assuming the turbine and the pump to be isentropic, determine the net
power produced and the utilization factor of the plant.
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10–68E
A large food-processing plant requires 2 lbm/s of saturated or slightly
superheated steam at 80 psia, which is extracted from the turbine of a
cogeneration plant. The boiler generates steam at 1000 psia and 1000°F
at a rate of 5 lbm/s,and the condenser pressure is 2 psia. Steam leaves
the process heater as a saturated liquid. It is then mixed with the
feedwater at the same pressure and this mixture is pumped to the boiler
pressure. Assuming both the pumps and the turbine have isentropic
efficiencies of 86 percent, determine (a) the rate of heat transfer to
the boiler and (b) the power output of the cogeneration plant.
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10–69
Steam is generated in the boiler of a cogeneration plant at 10 MPa and
450°C at a steady rate of 5 kg/s. In normal operation, steam expands in a
turbine to a pressure of 0.5 MPa and is then routed to the process
heater, where it supplies the process heat. Steam leaves the process
heater as a saturated liquid and is pumped to the boiler pressure. In
this mode, no steam passes through the condenser, which operates at 20
kPa. (a) Determine the power produced and the rate at which process heat
is supplied in this mode. (b) Determine the power produced and the rate
of process heat supplied if only 60 percent of the steam is routed to
the process heater and the remainder is expanded to the condenser
pressure.
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10–70
Consider a cogeneration power plant modified with regeneration. Steam
enters the turbine at 6 MPa and 450°C and expands to a pressure of 0.4
MPa. At this pressure, 60 percent of the steam is extracted from the
turbine, and the remainder expands to 10 kPa. Part of the extracted
steam is used to heat the feedwater in an open feedwater heater. The
rest of the extracted steam is used for process heating and leaves the
process heater as a saturated liquid at 0.4 MPa. It is subsequently
mixed with the feedwater leaving the feedwater heater, and the mixture
is pumped to the boiler pressure.
Assuming the turbines and the pumps to be isentropic, show the cycle on a
T-s diagram with respect to saturation lines, and determine the mass
flow rate of steam through the boiler for a net power output of 15 MW.
Get 10.70 exercise solution

10–71
Reconsider Prob. 10–70. Using EES (or other) software, investigate the
effect of the extraction pressure for removing steam from the turbine to
be used for the process heater and open feedwater heater on the
required mass flow rate. Plot the mass flow rate through the boiler as a
function of the extraction pressure, and discuss the results.
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10–72E
Steam is generated in the boiler of a cogeneration plant at 600 psia
and 800°F at a rate of 18 lbm/s. The plant is to produce power while
meeting the process steam requirements for a certain industrial
application. One-third of the steam leaving the boiler is throttled to a
pressure of 120 psia and is routed to the process heater. The rest of
the steam is expanded in an isentropic turbine to a pressure of 120 psia
and is also routed to the process heater. Steam leaves the process
heater at 240°F. Neglecting the pump work, determine (a) the net power
produced, (b) the rate of process heat supply, and (c) the utilization
factor of this plant.
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10–73
A cogeneration plant is to generate power and 8600 kJ/s of process
heat. Consider an ideal cogeneration steam plant. Steam enters the
turbine from the boiler at 7 MPa and 500°C. One-fourth of the steam is
extracted from the turbine at 600-kPa pressure for process heating. The
remainder of the steam continues to expand and exhausts to the condenser
at 10 kPa. The steam extracted for the process heater is condensed in
the heater and mixed with the feedwater at 600 kPa. The mixture is
pumped to the boiler pressure of 7 MPa. Show the cycle on a T-s diagram
with respect to saturation lines, and determine (a) the mass flow rate
of steam that must be supplied by the boiler, (b) the net power produced
by the plant, and (c) the utilization factor.
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10–74C In combined gas–steam cycles, what is the energy source for the steam?
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10–75C Why is the combined gas–steam cycle more efficient than either of the cycles operated alone?
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10–76
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.
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10–77
Consider a combined gas–steam power plant that has a net power output
of 450 MW. The pressure ratio of the gas-turbine cycle is 14. Air enters
the compressor at 300 K and the turbine at 1400 K. The combustion gases
leaving the gas turbine are used to heat the steam at 8 MPa to 400°C in
a heat exchanger. The combustion gases leave the heat exchanger at 460
K. An open feedwater heater incorporated with the steam cycle operates
at a pressure of 0.6 MPa. The condenser pressure is 20 kPa. Assuming all
the compression and expansion processes to be isentropic, 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.
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10–78
Reconsider Prob. 10–77. Using EES (or other) software, study the
effects of the gas cycle pressure ratio as it is varied from 10 to 20 on
the ratio of gas flow rate to steam flow rate and cycle thermal
efficiency. Plot your results as functions of gas cycle pressure ratio,
and discuss the results.
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10–79
Repeat Prob. 10–77 assuming isentropic efficiencies of 100 percent for
the pump, 82 percent for the compressor, and 86 percent for the gas and
steam turbines.
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10–80
Reconsider Prob. 10–79. Using EES (or other) software, study the
effects of the gas cycle pressure ratio as it is varied from 10 to 20 on
the ratio of gas flow rate to steam flow rate and cycle thermal
efficiency. Plot your results as functions of gas cycle pressure ratio,
and discuss the results.
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10–81
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°C at a rate of 10 kg/s and the gas turbine at 950°C.
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 heat exchanger at 200°C. Steam leaves the
high-pressure turbine at 1.0 MPa and is reheated to 400°C in the heat
exchanger before it expands in the lowpressure turbine. Assuming 80
percent isentropic efficiency for all pumps and turbine, determine (a)
the moisture content at the exit of the low-pressure turbine, (b) the
steam temperature at the inlet of the high-pressure turbine, (c) the net
power output and the thermal efficiency of the combined plant.
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10–82C What is a binary power cycle? What is its purpose?
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10–83C
By writing an energy balance on the heat exchanger of a binary vapor
power cycle, obtain a relation for the ratio of mass flow rates of two
fluids in terms of their enthalpies.
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10–84C Why is steam not an ideal working fluid for vapor power cycles?
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10–85C Why is mercury a suitable working fluid for the topping portion of a binary vapor cycle but not for the bottoming cycle?
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10–86C What is the difference between the binary vapor power cycle and the combined gas–steam power cycle?
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10–87
Show that the thermal efficiency of a combined gas–steam power plant
hcc can be expressed as hcc = hg + hs - hghs
where hg = Wg/Qin and hs = Ws/Qg,out are the thermal efficiencies of the
gas and steam cycles, respectively. Using this relation, determine the
thermal efficiency of a combined power cycle that consists of a topping
gas-turbine cycle with an efficiency of 40 percent and a bottoming
steam-turbine cycle with an efficiency of 30 percent.
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10–88
It can be shown that the thermal efficiency of a combined gas–steam
power plant hcc can be expressed in terms of the thermal efficiencies of
the gas- and the steam-turbine cycles as
hcc = hg + hs - hghs
Prove that the value of hcc is greater than either of hg or hs. That is,
the combined cycle is more efficient than either of the gas-turbine or
steam-turbine cycles alone.
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10–89
Consider a steam power plant operating on the ideal Rankine cycle with
reheat between the pressure limits of 25 MPa and 10 kPa with a maximum
cycle temperature of 600°C and a moisture content of 8 percent at the
turbine exit. For a reheat temperature of 600°C, determine the reheat
pressures of the cycle for the cases of (a) single and (b) double
reheat.
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10–90E
The Stillwater geothermal power plant in Nevada, which started full
commercial operation in 1986, is designed to operate with seven
identical units. Each of these seven units consists of a pair of power
cycles, labeled Level I and Level II, operating on the simple Rankine
cycle using an organic fluid as the working fluid. The heat source for
the plant is geothermal water (brine) entering the vaporizer (boiler) of
Level I of each unit at 325°F at a rate of 384,286 lbm/h and delivering
22.79 MBtu/h (“M” stands for “million”). The organic fluid that enters
the vaporizer at 202.2°F at a rate of 157,895 lbm/h leaves it at 282.4°F
and 225.8 psia as saturated vapor. This saturated vapor expands in the
turbine to 95.8°F and 19.0 psia and produces 1271 kW of electric power.
About 200 kW of this power is used by the pumps, the auxiliaries, and
the six fans of the condenser. Subsequently, the organic working fluid
is condensed in an air-cooled condenser by air that enters the condenser
at 55°F at a rate of 4,195,100 lbm/h and leaves at 84.5°F. The working
fluid is pumped and then preheated in a preheater to 202.2°F by
absorbing 11.14 MBtu/h of heat from the geothermal water (coming from
the vaporizer of Level II) entering the preheater at 211.8°F and leaving
at 154.0°F. Taking the average specific heat of the geothermal water to
be 1.03 Btu/lbm · °F, determine (a) the exit temperature of the
geothermal water from the vaporizer, (b) the rate of heat rejection from
the working fluid to the air in the condenser, (c) the mass flow rate
of the geothermal water at the preheater, and (d) the thermal efficiency
of the Level I cycle of this geothermal power plant.
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10–91
Steam enters the turbine of a steam power plant that operates on a
simple ideal Rankine cycle at a pressure of 6 MPa, and it leaves as a
saturated vapor at 7.5 kPa. Heat is transferred to the steam in the
boiler at a rate of 40,000 kJ/s. Steam is cooled in the condenser by the
cooling water from a nearby river, which enters the condenser at 15°C.
Show the cycle on a T-s diagram with respect to saturation lines, and
determine (a) the turbine inlet temperature, (b) the net power output
and thermal efficiency, and (c) the minimum mass flow rate of the
cooling water required.
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10–92
A steam power plant operates on an ideal Rankine cycle with two stages
of reheat and has a net power output of 120 MW. Steam enters all three
stages of the turbine at 500°C. The maximum pressure in the cycle is 15
MPa, and the minimum pressure is 5 kPa. Steam is reheated at 5 MPa the
first time and at 1 MPa the second time. Show the cycle on a T-s diagram
with respect to saturation lines, and determine (a) the thermal
efficiency of the cycle and (b) the mass flow rate of the steam.
Answers: (a) 45.5 percent, (b) 64.4 kg/s
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10–93
Consider a steam power plant that operates on a regenerative Rankine
cycle and has a net power output of 150 MW. Steam enters the turbine at
10 MPa and 500°C and the condenser at 10 kPa. The isentropic efficiency
of the turbine is 80 percent, and that of the pumps is 95 percent. Steam
is extracted from the turbine at 0.5 MPa to heat the feedwater in an
open feedwater heater. Water leaves the feedwater heater as a saturated
liquid. Show the cycle on a T-s diagram, and determine (a) the mass flow
rate of steam through the boiler and (b) the thermal efficiency of the
cycle. Also, determine the exergy destruction associated with the
regeneration process. Assume a source temperature of 1300 K and a sink
temperature of 303 K.
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10–94 Repeat Prob. 10–93 assuming both the pump and the turbine are isentropic.
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10–95
Consider an ideal reheat–regenerative Rankine cycle with one open
feedwater heater. The boiler pressure is 10 MPa, the condenser pressure
is 15 kPa, the reheater pressure is 1 MPa, and the feedwater pressure is
0.6 MPa. Steam enters both the high- and low-pressure turbines at
500°C. Show the cycle on a T-s diagram with respect to saturation lines,
and determine (a) the fraction of steam extracted for regeneration and
(b) the thermal efficiency of the cycle
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10–96 Repeat Prob. 10–95 assuming an isentropic efficiency of 84 percent for the turbines and 100 percent for the pumps.
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10–97
A steam power plant operates on an ideal reheat– regenerative Rankine
cycle with one reheater and two feedwater heaters, one open and one
closed. Steam enters the high-pressure turbine at 15 MPa and 600°C and
the lowpressure turbine at 1 MPa and 500°C. The condenser pressure is 5
kPa. Steam is extracted from the turbine at 0.6 MPa for the closed
feedwater heater and at 0.2 MPa for the open feedwater heater. In the
closed feedwater heater, the feedwater is heated to the condensation
temperature of the extracted steam. The extracted steam leaves the
closed feedwater heater as a saturated liquid, which is subsequently
throttled to the open feedwater heater. Show the cycle on a T-s diagram
with respect to saturation lines. Determine (a) the fraction of steam
extracted from the turbine for the open feedwater heater, (b) the
thermal efficiency of the cycle, and (c) the net power output for a mass
flow rate of 42 kg/s through the boiler.
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10–98
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 pressure of 15 kPa. The condensate from the condenser is
pumped to 1 MPa and is mixed with the extracted steam, which leaves the
process heater as a compressed liquid at 120°C. The mixture is then
pumped to the boiler pressure. Assuming the turbine to be isentropic,
show the cycle on a T-s diagram with respect to saturation lines, and
disregarding pump work, determine (a) the rate of heat input in the
boiler and (b) the fraction of steam extracted for process heating.
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10–99
The gas-turbine cycle of a combined gas–steam power plant has a
pressure ratio of 8. Air enters the compressor at 290 K and the turbine
at 1400 K. The combustion gases leaving the gas turbine are used to heat
the steam at 15 MPa to 450°C in a heat exchanger. The combustion gases
leave the heat exchanger at 247°C. Steam expands in a highpressure
turbine to a pressure of 3 MPa and is reheated in the combustion chamber
to 500°C before it expands in a lowpressure turbine to 10 kPa. The mass
flow rate of steam is 30 kg/s. Assuming all the compression and
expansion processes to be isentropic, determine (a) the mass flow rate
of air in the gas-turbine cycle, (b) the rate of total heat input, and
(c) the thermal efficiency of the combined cycle.
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10–100
Repeat Prob. 10–99 assuming isentropic efficiencies of 100 percent for
the pump, 80 percent for the compressor, and 85 percent for the gas and
steam turbines.
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10–101
Starting with Eq. 10–20, show that the exergy destruction associated
with a simple ideal Rankine cycle can be expressed as i = qin(hth,Carnot
- hth), where hth is efficiency of the Rankine cycle and hth,Carnot is
the efficiency of the Carnot cycle operating between the same
temperature limits.
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10–102
Steam is to be supplied from a boiler to a highpressure turbine whose
isentropic efficiency is 75 percent at conditions to be determined. The
steam is to leave the high-pressure turbine as a saturated vapor at 1.4
MPa, and the turbine is to produce 1 MW of power. Steam at the turbine
exit is extracted at a rate of 1000 kg/min and routed to a process
heater while the rest of the steam is supplied to a low-pressure turbine
whose isentropic efficiency is 60 percent. The low-pressure turbine
allows the steam to expand to 10 kPa pressure and produces 0.8 MW of
power. Determine the temperature, pressure, and the flow rate of steam
at the inlet of the high-pressure turbine.
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10–103
A textile plant requires 4 kg/s of saturated steam at 2 MPa, which is
extracted from the turbine of a cogeneration plant. Steam enters the
turbine at 8 MPa and 500°C at a rate of 11 kg/s and leaves at 20 kPa.
The extracted steam leaves the process heater as a saturated liquid and
mixes with the feedwater at constant pressure. The mixture is pumped to
the boiler pressure. Assuming an isentropic efficiency of 88 percent for
both the turbine and the pumps, determine (a) the rate of process heat
supply, (b) the net power output, and (c) the utilization factor of the
plant.
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10–104
Using EES (or other) software, investigate the effect of the condenser
pressure on the performance of a simple ideal Rankine cycle. Turbine
inlet conditions of steam are maintained constant at 5 MPa and 500°C
while the condenser pressure is varied from 5 to 100 kPa. Determine the
thermal efficiency of the cycle and plot it against the condenser
pressure, and discuss the results.
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10–105
Using EES (or other) software, investigate the effect of the boiler
pressure on the performance of a simple ideal Rankine cycle. Steam
enters the turbine at 500°C and exits at 10 kPa. The boiler pressure is
varied from 0.5 to 20 MPa. Determine the thermal efficiency of the cycle
and plot it against the boiler pressure, and discuss the results.
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10–106
Using EES (or other) software, investigate the effect of superheating
the steam on the performance of a simple ideal Rankine cycle. Steam
enters the turbine at 3 MPa and exits at 10 kPa. The turbine inlet
temperature is varied from 250 to 1100°C. Determine the thermal
efficiency of the cycle and plot it against the turbine inlet
temperature, and discuss the results.
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10–107
Using EES (or other) software, investigate the effect of reheat
pressure on the performance of an ideal Rankine cycle. The maximum and
minimum pressures in the cycle are 15 MPa and 10 kPa, respectively, and
steam enters both stages of the turbine at 500°C. The reheat pressure is
varied from 12.5 to 0.5 MPa. Determine the thermal efficiency of the
cycle and plot it against the reheat pressure, and discuss the results.
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10–108
Using EES (or other) software, investigate the effect of number of
reheat stages on the performance of an ideal Rankine cycle. The maximum
and minimum pressures in the cycle are 15 MPa and 10 kPa, respectively,
and steam enters all stages of the turbine at 500°C. For each case,
maintain roughly the same pressure ratio across each turbine stage.
Determine the thermal efficiency of the cycle and plot it against the
number of reheat stages 1, 2, 4, and 8, and discuss the results.
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10–109
Using EES (or other) software, investigate the effect of extraction
pressure on the performance of an ideal regenerative Rankine cycle with
one open feedwater heater. Steam enters the turbine at 15 MPa and 600°C
and the condenser at 10 kPa. Determine the thermal efficiency of the
cycle, and plot it against extraction pressures of 12.5, 10, 7, 5, 2, 1,
0.5, 0.1, and 0.05 MPa, and discuss the results.
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10–110
Using EES (or other) software, investigate the effect of the number of
regeneration stages on the performance of an ideal regenerative Rankine
cycle. Steam enters the turbine at 15 MPa and 600°C and the condenser at
5 kPa. For each case, maintain about the same temperature difference
between any two regeneration stages. Determine the thermal efficiency of
the cycle, and plot it against the number of regeneration stages for 1,
2, 3, 4, 5, 6, 8, and 10 regeneration stages. Fundamentals of
Engineering (FE) Exam Problems
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10–111
Consider a steady-flow Carnot cycle with water as the working fluid
executed under the saturation dome between the pressure limits of 8 MPa
and 20 kPa. Water changes from saturated liquid to saturated vapor
during the heat addition process. The net work output of this cycle is
(a) 494 kJ/kg (b) 975 kJ/kg (c) 596 kJ/kg (d) 845 kJ/kg (e) 1148 kJ/kg
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10–112
A simple ideal Rankine cycle operates between the pressure limits of 10
kPa and 3 MPa, with a turbine inlet temperature of 600°C. Disregarding
the pump work, the cycle efficiency is (a) 24 percent (b) 37 percent (c)
52 percent (d) 63 percent (e) 71 percent
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10–113
A simple ideal Rankine cycle operates between the pressure limits of 10
kPa and 5 MPa, with a turbine inlet temperature of 600°C. The mass
fraction of steam that condenses at the turbine exit is (a) 6 percent
(b) 9 percent (c) 12 percent (d) 15 percent (e) 18 percent
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10–114
A steam power plant operates on the simple ideal Rankine cycle between
the pressure limits of 10 kPa and 10 MPa, with a turbine inlet
temperature of 600°C. The rate of heat transfer in the boiler is 800
kJ/s. Disregarding the pump work, the power output of this plant is (a)
243 kW (b) 284 kW (c) 508 kW (d) 335 kW (e) 800 kW
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10–115
Consider a combined gas-steam power plant. Water for the steam cycle is
heated in a well-insulated heat exchanger by the exhaust gases that
enter at 800 K at a rate of 60 kg/s and leave at 400 K. Water enters the
heat exchanger at 200°C and 8 MPa and leaves at 350°C and 8 MPa. If the
exhaust gases are treated as air with constant specific heats at room
temperature, the mass flow rate of water through the heat exchanger
becomes (a) 11 kg/s (b) 24 kg/s (c) 46 kg/s (d) 53 kg/s (e) 60 kg/s
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10–116
An ideal reheat Rankine cycle operates between the pressure limits of
10 kPa and 8 MPa, with reheat occurring at 4 MPa. The temperature of
steam at the inlets of both turbines is 500°C, and the enthalpy of steam
is 3185 kJ/kg at the exit of the high-pressure turbine, and 2247 kJ/kg
at the exit of the low-pressure turbine. Disregarding the pump work, the
cycle efficiency is (a) 29 percent (b) 32 percent (c) 36 percent (d) 41
percent (e) 49 percent
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10–117
Pressurized feedwater in a steam power plant is to be heated in an
ideal open feedwater heater that operates at a pressure of 0.5 MPa with
steam extracted from the turbine. If the enthalpy of feedwater is 252
kJ/kg and the enthalpy of extracted steam is 2665 kJ/kg, the mass
fraction of steam extracted from the turbine is (a) 4 percent (b) 10
percent (c) 16 percent (d) 27 percent (e) 12 percent
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10–118
Consider a steam power plant that operates on the regenerative Rankine
cycle with one open feedwater heater. The enthalpy of the steam is 3374
kJ/kg at the turbine inlet, 2797 kJ/kg at the location of bleeding, and
2346 kJ/kg at the turbine exit. The net power output of the plant is 120
MW, and the fraction of steam bled off the turbine for regeneration is
0.172. If the pump work is negligible, the mass flow rate of steam at
the turbine inlet is (a) 117 kg/s (b) 126 kg/s (c) 219 kg/s (d) 268 kg/s
(e) 679 kg/s
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10–119
Consider a simple ideal Rankine cycle. If the condenser pressure is
lowered while keeping turbine inlet state the same, (a) the turbine work
output will decrease. (b) the amount of heat rejected will decrease.
(c) the cycle efficiency will decrease. (d) the moisture content at
turbine exit will decrease. (e) the pump work input will decrease.
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10–120
Consider a simple ideal Rankine cycle with fixed boiler and condenser
pressures. If the steam is superheated to a higher temperature, (a) the
turbine work output will decrease. (b) the amount of heat rejected will
decrease. (c) the cycle efficiency will decrease. (d) the moisture
content at turbine exit will decrease. (e) the amount of heat input will
decrease.
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10–121
Consider a simple ideal Rankine cycle with fixed boiler and condenser
pressures. If the cycle is modified with reheating, (a) the turbine work
output will decrease. (b) the amount of heat rejected will decrease.
(c) the pump work input will decrease. (d) the moisture content at
turbine exit will decrease. (e) the amount of heat input will decrease.
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10–122
Consider a simple ideal Rankine cycle with fixed boiler and condenser
pressures. If the cycle is modified with regeneration that involves one
open feedwater heater (select the correct statement per unit mass of
steam flowing through the boiler), (a) the turbine work output will
decrease. (b) the amount of heat rejected will increase. (c) the cycle
thermal efficiency will decrease. (d) the quality of steam at turbine
exit will decrease. (e) the amount of heat input will increase.
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10–123
Consider a cogeneration power plant modified with regeneration. Steam
enters the turbine at 6 MPa and 450°C at a rate of 20 kg/s and expands
to a pressure of 0.4 MPa. At this pressure, 60 percent of the steam is
extracted from the turbine, and the remainder expands to a pressure of
10 kPa. Part of the extracted steam is used to heat feedwater in an open
feedwater heater. The rest of the extracted steam is used for process
heating and leaves the process heater as a saturated liquid at 0.4 MPa.
It is subsequently mixed with the feedwater leaving the feedwater
heater, and the mixture is pumped to the boiler pressure. The steam in
the condenser
is cooled and condensed by the cooling water from a nearby river, which
enters the adiabatic condenser at a rate of 463 kg/s. 1. The total power
output of the turbine is (a) 17.0 MW (b) 8.4 MW (c) 12.2 MW (d) 20.0 MW
(e) 3.4 MW 2. The temperature rise of the cooling water from the river
in the condenser is (a) 8.0°C (b) 5.2°C (c) 9.6°C (d) 12.9°C (e) 16.2°C
3. The mass flow rate of steam through the process heater is (a) 1.6
kg/s (b) 3.8 kg/s (c) 5.2 kg/s (d) 7.6 kg/s (e) 10.4 kg/s 4. The rate of
heat supply from the process heater per unit mass of steam passing
through it is (a) 246 kJ/kg (b) 893 kJ/kg (c) 1344 kJ/kg (d) 1891 kJ/kg
(e) 2060 kJ/kg 5. The rate of heat transfer to the steam in the boiler
is (a) 26.0 MJ/s (b) 53.8 MJ/s (c) 39.5 MJ/s (d) 62.8 MJ/s (e) 125.4
MJ/s
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