ENTC 489: Announcements

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ENTC 489 Announcements

• Homework assignment No. 4
• Assigned Problems from Introduction to Thermal
  and Fluids Engineering (Kaminski and Jensen)
• 8.20, 8.24, 8.29, 8.32
• Due Thursday, October 8th before 1050 am
• For more information, go to
• http//etidweb.tamu.edu/classes/entc489/502/Index.
  htm
• Thermodynamics
• Review of Rankine Cycles
• Review Ideal and Actual
• New Reheat, Regenerative, and others

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ENTC 489 Announcements

• Exam I
• Tentatively 20 or 22 Oct 2009
• After HW 5
• Fluid systems
• Power (Rankine) Cycles
• Review Ideal and Actual
• New
• Reheat
• Regenerative
• Cogeneration
• Brayton Cycle (Review)
• Combined Cycle (Brayton Rankine)

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Orientation Meeting October 8th, 730Pm Thompson
122 FREE FOOD
Come to meet people in your major, get involved
in your nationally-recognized engineering
society, learn about professional life after
college, and get a free meal during these hard
times! ?
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Ideal Regenerative Rankine Cycle

• Ideal Rankine Cycle concern
• Lower than ideal average temperature in the
  boiler
• Solution Use a regenerator or feedwater heater
  (FWH) to raise water temperature before boiler
• Two types of Feedwater Heaters
• Open FWH
• Closed FWH

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(No Transcript)
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Regenerative Rankine Cycle(Open FWH)
Advantages Simple, inexpensive, and with good
heat transfer characteristics Disadvantage A
second pump is required for both streams
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Regenerative Rankine Cycle(Closed FWH)
Advantages Each pump handles a fraction of the
total flow Disadvantages More complex (need
heat exchanger inside FWH), and more expensive
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Combined Open and Closed FWH (Regenerative) Cycle
Trap Enthalpy remains constant across it use
to throttle to lower pressure
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Equations for Regenerative Rankine Cycle (Open
FWH)
Note h3 hf at FWH pressure
Use first Law of Thermodynamics for open system
(mixing chamber FWH) to find (y)
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Regenerative Cycle Example

• A steam power plant operates on the ideal
  regenerative Rankine cycle with one open
  feedwater heater (FWH). Steam enters the turbine
  at 15 MPa and 600 C, and is condensed at a
  pressure of 10 kPa. Some (y) steam leaves the
  turbine at a pressure of 1.2 MPa, and enters the
  FWH. Determine (y), and, the thermal efficiency
  of the cycle.

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Cogeneration

• Production of more than one useful form of energy
  (process heat and electric power) from the same
  energy source

With cogeneration
No cogeneration
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Cogeneration

• Utilization factor eu

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Gas Turbines Turbofan
http//education.rolls-royce.com/how-a-gas-turbine
-works/
http//www.green-energy-news.com/arch/nrgs2008/200
80093.html
http//www.b-domke.de/AviationImages/Rarebird/Imag
es/0809.jpg
http//www.flightglobal.com/assets/getasset.aspx?I
temID18032
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Gas Turbines Brayton Cycle
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Gas Turbines Brayton Cycle
Working fluid Air (ideal gas)
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Brayton Cycle
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Brayton Cycle

• Open system

Using Isentropic Relations
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Brayton Cycle How to find hs

• Working fluid Air (use air table)
• T1 ? h1 Pr1
• T3 ? h3 Pr3
• Use rp and Pr1 to find T2 and h2
• Use rp and Pr3 to find T4 and h4

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Example

• A stationary power plant has a pressure ratio of
  8. The gas temperature entering the compressor
  is 300 K, and 1300 K at the turbine inlet.
  Determine the gas temperature at the exits of the
  compressor and turbine, the back work ratio, and
  the thermal efficiency.

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Turbine

• Isentropic efficiency

Energy loss due to irreversibilities
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Compressors

• Isentropic efficiency

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Example

• Assuming a compressor efficiency of 80, and a
  turbine efficiency of 85, determine the back
  work ratio, thermal efficiency, and the turbine
  exit temperature of the previous example