ChemE 260 Isobaric and Isochoric Processes, Thermodynamic Cycles

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ChemE 260 Isobaric and Isochoric
Processes,Thermodynamic Cycles

• Dr. William Baratuci
• Senior Lecturer
• Chemical Engineering Department
• University of Washington
• TCD 4 E FCB 4 Supplements (2)

April 12, 2005
2
Isobaric Processes

• P constant
• 1st Law
• closed system, integral form
• Assume ?Epot 0 and ?Ekin 0
• IF boundary work is theonly form of work
• Definition of boundary work
• 1st Law becomes

Baratuci ChemE 260 April 12, 2005
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Isochoric Processes

• V constant
• 1st Law
• closed system, integral form
• Assume ?Epot 0 and ?Ekin 0
• IF boundary work is theonly form of work
• Definition of boundary work
• 1st Law becomes

Baratuci ChemE 260 April 12, 2005
4
Cycle Types and Characterization

• Three types of cycles
• Power Cycles or Heat Engines
• Refrigeration Cycles
• Heat Pump Cycles
• How to Categorize Systems that Undergo Cycles
• Open vs. Closed Cycles
• Closed Cycles use a working fluid that never
  leaves the system
• Open Cycles take in fresh fluid and reject the
  used fluid when the cycle is complete.
  Usually the fluid is air.
• Gas vs. Vapor Cycles
• Vapor Cycles take advantage of a phase change in
  the fluid
• Gas Cycles the fluid always remains in the gas
  phase. The fluid is usually air or an air-fuel
  mixture (as in an internal combustion engine).

Baratuci ChemE 260 April 12, 2005
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Power Cycles

• 1st Law
• Tie-fighter Diagrams
• No sign convention !All quantities are positive.
• 1st Law
• Thermal Efficiency

Baratuci ChemE 260 April 12, 2005
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Refrigeration Cycles

• 1st Law
• Tie-fighter Diagram
• No sign convention !All quantities are positive.
• 1st Law
• Coefficient of Performance

Baratuci ChemE 260 April 12, 2005
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Heat Pump Cycles

• 1st Law
• Tie-fighter Diagram
• No sign convention !All quantities are positive.
• 1st Law
• Coefficient of Performance

Baratuci ChemE 260 April 12, 2005
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Next Class

• Problem Session
• After that
• Chapter 5 1st Law of Thermodynamics for Open
  Systems
• After that
• Review for Test 1
• After that
• Test 1

Baratuci ChemE 260 April 12, 2005