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ENGR 224 – Thermodynamics

Final Exam – Outline Spring 2011


Chapter 9 – Power Systems

• Vapor Power Cycle: The Rankine Cycle
o Closed cycle: working fluid is recycledo Water is usually the working fluid
o Evaporator and condenser used for isobaric heat transfer steps
o Minimizes cavitation in the pump and provides for the possibility ofsuperheating the turbine feed to increase turbine effluent quality.
o Ideal Rankine Cycle
▪ Pump and turbine are isentropic
▪ Condenser effluent is a saturatedliquid
▪ Turbine feed is a saturated vapor
o Improvements
▪ Superheat: improves turbine effluent quality and increases (th
▪ Supercritical:increases (th, high T & P requires expensive materials
▪ Reheat: decreases (th unless used with regeneration, but increases turbine effluent quality
▪ Regeneration: Preheatboiler feed using HP turbine effluent
• Increases (th
• Great in combination with reheat
• Open and closed feedwater heaters are used▪ Binary: Two Rankine Cycles with different working fluids
• Big increase in (th
• Can reach high temperatures and efficiencies withoutusing high pressures
▪ Cogeneration
• Use some or al of the HP turbine effluent in another process.
• Saturated liquid is returned from theother process.

• Gas Power Cycles: The Brayton Cycle
o Air-Standard Assumptions
▪ Air is the working fluid and it behaves as an ideal gas
▪ Modeled as aclosed cycle
• A 2nd HEX is used to restore the working fluid to its initial state and close the system
▪ Internal combustion replaced by external combustion and...