Question

1. You are to do a preliminary design study for a small
demonstration steam turbine power plant.

- Steam will be provided by a small steam generator fired by
natural gas. - Your system will take in steam at 30 bar
and 400 oC.

- The steam passes through a two stage turbine. At a pressure of 10
bars, the steam leaves the first stage of the turbine and will pass
through a reheat loop in the steam generator which will boost the
temperature back up to 400 oC at this pressure. The steam will then
enter the second stage of the turbine.

- When the steam leaves the turbine, the quality should be at least
95% at the turbine exit / condenser inlet.

- The design condenser pressure is 0.70
bar.

- Heat is removed from the condenser and rejected to the
environment through a cooling tower.

a) Assuming isentropic expansion, what are the temperature,
enthalpy, and entropy of the steam when it leaves the first stage
of the turbine? (5 pts)

b) What are the enthalpy and the entropy of the steam as it leaves
the reheater and enters the second stage of the turbine? How much
heat (kJ/kg) goes into the steam in the reheat process? (10
pts)

c) Based on an isentropic expansion, what will the quality be at
the exit? Will it meet this design limit? (10 pts)

For the following parts use the design turbine power output of 2.5
kW.

d) What mass flow rate is required? (10 pts)

e) At what rate must heat be produced by natural gas burners in the
steam generator to produce the steam at the turbine inlet, and how
much heat must be produced to reheat the steam between the stages?
For a heating rate range of 950-1150 BTU/scf and a cost of $8 per
100 cubic feet, what is the fuel cost per hour to run this unit?
(10 pts)

f) What is the feed water pump power demand, and what is the BWR?
(10 pts)

Answer #1

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...

A steam turbine has inlet steam pressure p1 = 1.4 MPa
absolute. Inlet steam temperature is T1 = 400
oC. This corresponds to inlet enthalpy per unit mass of
h1 = 3121 kJ/kg. Exit pressure of the steam is p2 = 101
kPa absolute. Exit steam temperature is T2 = 100
oC. This corresponds to exit enthalpy per unit mass of
h2 = 2676 kJ/kg. Inlet speed of the steam is
V1 = 15 m/s and exit speed is V2...

Water is the working fluid in a Rankine cycle with reheat.
Superheated vapor enters the turbine at 10 MPa, 520°C, and the
condenser pressure is 6 kPa. Steam expands through the first-stage
turbine to 0.7 MPa and then is reheated to 520°C. The pump and each
turbine stage have an isentropic efficiency of 70%.
Determine for the cycle:
(a) the heat addition, in kJ per kg of steam entering the
first-stage turbine.
(b) the percent thermal efficiency.
(c) the magnitude...

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,...

A
steam power plant operates with a high pressure of 4 MPa and has a
boiler exit at 600C recieving heat from 700C reservoir. The ambient
air at 20C provides cooling to maintain the water/vapor mixture in
the condenser at 60C. All components are ideal (reversible) except
the turbine which has an efficientcy 92% of a reversible,
isentropic process. other than that the irreversibility of the
turbine, the power plant can be considered as a Rankine cycle.
Determine the following...

Consider a steam power plant which operates on the Rankine
cycle. The pressures in the boiler and the condenser are 5000 kPa
and 40 kPa, respectively. The temperatures at the inlet of the
turbine and at the inlet of the pump are 500oC and 70oC,
respectively. The isentropic efficiency of the turbine is 94
percent, pressure and pump losses are negligible. If the mass flow
rate of steam is 10 kg/s. Determine (a) the heat transfer rate in
the boiler,...

A power plant operates on a regenerative vapor power cycle with
one open feedwater heater. Steam enters the first turbine stage at
12 MPa, 560°C and expands to 1 MPa, where some of the steam is
extracted and diverted to the open feedwater heater operating at 1
MPa. The remaining steam expands through the second turbine stage
to the condenser pressure of 17 kPa. Saturated liquid exits the
open feedwater heater at 1 MPa. The net power output for the...

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 power plant using an ideal Rankine power generation
cycle operates at an efficiency of 55% with a flowrate of steam of
2 kg/s. Heat is supplied to the boiler of 2500 kJ/kg. The
pump takes in saturated liquid water at 100 kPa and has an exit
pressure of 10 MPa. Determine:
the exit temperature of the pump (oC) (3
pts)
the work of the turbine (kW) (3 pts)
the heat exhausted from the condenser (kJ/s) (3
pts)

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...

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