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Faculty of Engineering Technology, Universiti Malaysia Perlis (UniMAP)
PDT 277 – APPLIED THERMODYNAMICS
Prepared by:
Mohd Al-Hafiz Mohd Nawi, Eng.D.
Department of Mechanical Engineering Technology,
Faculty of Engineering Technology (FE-Tech),
Universiti Malaysia Perlis (UniMAP) Perlis.
Chapter 7:
Vapor & Combined Power Cycles
(Answer)
Lecturer Info
DEPARTMENT OF MECHANICAL ENGINEERING TECHNOLOGY,FACULTY OF ENGINEERING TECHNOLOGY,
UNIVERSITI MALAYSIA PERLIS (UniMAP)
Exercise
PDT277 – APPLIED THERMODYNAMICS UNIT 7 – VAPOR & COMBINED POWER CYCLES
[1] Why is the Carnot cycle not a realistic model for steam power
plants?
Answer
The Carnot cycle is not a realistic model for steam power plantsbecause (1) limiting the heat transfer processes to two-phase
systems to maintain isothermal conditions severely limits the
maximum temperature that can be used in the cycle, (2) the
turbine will have to handle steam with a high moisture content
which causes erosion, and (3) it is not practical to design a
compressor that will handle two phases.
[2] How do actual vapor power cycles differ from idealized ones?
Answer
The actual vapor power cycles differ from the idealized ones inthat the actual cycles involve friction and pressure drops in various
components and the piping, and heat loss to the surrounding
medium from these components and piping.
Lecturer Info
DEPARTMENT OF MECHANICAL ENGINEERING TECHNOLOGY,FACULTY OF ENGINEERING TECHNOLOGY,
UNIVERSITI MALAYSIA PERLIS (UniMAP)
Exercise
PDT277 – APPLIED THERMODYNAMICS UNIT 7 – VAPOR & COMBINED POWER CYCLES
[3] Is it possible to maintain a pressure of 10 kPa in a condenser that isbeing cooled by river water entering at 20 °C?
Answer
Yes, because the saturation temperature of steam at 10 kPa is
45.81°C, which is much higher than the temperature of the cooling
water.
Lecturer Info
DEPARTMENT OF MECHANICAL ENGINEERING TECHNOLOGY,FACULTY OF ENGINEERING TECHNOLOGY,
UNIVERSITI MALAYSIA PERLIS (UniMAP)
Exercise
PDT277 – APPLIED THERMODYNAMICS UNIT 7 – VAPOR & COMBINED POWER CYCLES
[4] A steady-flow Carnot cycle uses water as the working fluid. Water
changes from saturated liquid to saturated vapor as heat istransferred 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, and (c) the net work
output.
Lecturer Info
DEPARTMENT OF MECHANICAL ENGINEERING TECHNOLOGY,FACULTY OF ENGINEERING TECHNOLOGY,
UNIVERSITI MALAYSIA PERLIS (UniMAP)
Exercise
PDT277 – APPLIED THERMODYNAMICS UNIT 7 – VAPOR & COMBINED POWER CYCLES
[5] Consider a steady-flow Carnot cycle with water as the working
fluid. The maximum and minimum temperatures in the cycle are350 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.
Lecturer Info
DEPARTMENT OF MECHANICAL ENGINEERING TECHNOLOGY,FACULTY OF ENGINEERING TECHNOLOGY,
UNIVERSITI MALAYSIA PERLIS (UniMAP)
Exercise
PDT277 – APPLIED THERMODYNAMICS UNIT 7 – VAPOR & COMBINED POWER CYCLES
[6] A steam power plant operates on a simple ideal Rankine cycle
between the pressure limits of 3 MPa and 50 kPa. The temperatureof 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.
Lecturer Info
DEPARTMENT OF MECHANICAL ENGINEERING TECHNOLOGY,FACULTY OF ENGINEERING TECHNOLOGY,
UNIVERSITI MALAYSIA PERLIS (UniMAP)
Exercise
PDT277 – APPLIED THERMODYNAMICS UNIT 7 – VAPOR & COMBINED POWER CYCLES
[6] A steam power plant operates on a simple ideal Rankine cycle
between the pressure limits of 3 MPa and 50 kPa. The temperatureof 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.
Lecturer Info
DEPARTMENT OF MECHANICAL ENGINEERING TECHNOLOGY,FACULTY OF ENGINEERING TECHNOLOGY,
UNIVERSITI MALAYSIA PERLIS (UniMAP)
Exercise
PDT277 – APPLIED THERMODYNAMICS UNIT 7 – VAPOR & COMBINED POWER CYCLES
[7] Refrigerant-134a is used as the working fluid in a simple ideal
Rankine cycle which operates the boiler at 2000 kPa and thecondenser at 24 °C. The mixture at the exit of the turbine has a
quality of 93 percent. Determine the turbine inlet temperature, the
cycle thermal efficiency, and the back-work ratio of this cycle.
Lecturer Info
DEPARTMENT OF MECHANICAL ENGINEERING TECHNOLOGY,FACULTY OF ENGINEERING TECHNOLOGY,
UNIVERSITI MALAYSIA PERLIS (UniMAP)
Exercise
PDT277 – APPLIED THERMODYNAMICS UNIT 7 – VAPOR & COMBINED POWER CYCLES
[7] Refrigerant-134a is used as the working fluid in a simple ideal
Rankine cycle which operates the boiler at 2000 kPa and thecondenser at 24 °C. The mixture at the exit of the turbine has a
quality of 93 percent. Determine the turbine inlet temperature, the
cycle thermal efficiency, and the back-work ratio of this cycle.
Lecturer Info
DEPARTMENT OF MECHANICAL ENGINEERING TECHNOLOGY,FACULTY OF ENGINEERING TECHNOLOGY,
UNIVERSITI MALAYSIA PERLIS (UniMAP)
Exercise
PDT277 – APPLIED THERMODYNAMICS UNIT 7 – VAPOR & COMBINED POWER CYCLES
[8] A simple ideal Rankine cycle as in figure below which uses wateras the working fluid operates its condenser at 40 °C and its boiler
at 300 °C. Calculate the work produced by the turbine, the heat
supplied in the boiler, and the thermal efficiency of this cycle
when the steam enters the turbine without any superheating.
Lecturer Info
DEPARTMENT OF MECHANICAL ENGINEERING TECHNOLOGY,FACULTY OF ENGINEERING TECHNOLOGY,
UNIVERSITI MALAYSIA PERLIS (UniMAP)
Exercise
PDT277 – APPLIED THERMODYNAMICS UNIT 7 – VAPOR & COMBINED POWER CYCLES
[8] A simple ideal Rankine cycle as in figure below which uses wateras the working fluid operates its condenser at 40 °C and its boiler
at 300 °C. Calculate the work produced by the turbine, the heat
supplied in the boiler, and the thermal efficiency of this cycle
when the steam enters the turbine without any superheating.
Lecturer Info
DEPARTMENT OF MECHANICAL ENGINEERING TECHNOLOGY,FACULTY OF ENGINEERING TECHNOLOGY,
UNIVERSITI MALAYSIA PERLIS (UniMAP)
Exercise
PDT277 – APPLIED THERMODYNAMICS UNIT 7 – VAPOR & COMBINED POWER CYCLES
[8] A simple ideal Rankine cycle as in figure below which uses wateras the working fluid operates its condenser at 40 °C and its boiler
at 300 °C. Calculate the work produced by the turbine, the heat
supplied in the boiler, and the thermal efficiency of this cycle
when the steam enters the turbine without any superheating.
Lecturer Info
DEPARTMENT OF MECHANICAL ENGINEERING TECHNOLOGY,FACULTY OF ENGINEERING TECHNOLOGY,
UNIVERSITI MALAYSIA PERLIS (UniMAP)
Exercise
PDT277 – APPLIED THERMODYNAMICS UNIT 7 – VAPOR & COMBINED POWER CYCLES
[9] 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.
Lecturer Info
DEPARTMENT OF MECHANICAL ENGINEERING TECHNOLOGY,FACULTY OF ENGINEERING TECHNOLOGY,
UNIVERSITI MALAYSIA PERLIS (UniMAP)
Exercise
PDT277 – APPLIED THERMODYNAMICS UNIT 7 – VAPOR & COMBINED POWER CYCLES
[9] 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.