Transcript Thermodynamics I

Brayton cycle analysis
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Collect solutions
Energy report
Due 4/16; 15% of grade
 Select one of the following energy
generation processes
• Nuclear power
• Solar power
• Wind power
• Fuel cell
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Energy report
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Prepare a report supporting your choice as
the most promising energy source for the
future.
Rankine cycle
1 → 2 isentropic expansion; turbine
 2 → 3 constant pressure heat rejection;
condenser
 3 → 4 isentropic compression; feed water
pump
 4 → 1 constant pressure heat addition; steam
generator
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Cycle analysis
Each process a control volume: use h & s
as needed
 Limited information on compressed liquid
 Net work of cycle
 Thermal efficiency
 bwr
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Cycle improvements
Higher pressure
 Lower pressure
 Superheat
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Rankine Cycle
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Water is the working fluid in an ideal Rankine
cycle. Pressure & temperature at the turbine
inlet are 1600psi & 1100oF. Condenser
pressure is 1psi. Mass flow of steam is 1.4x106
lbm/hr. Cooling water experiences a
temperature increase from 60oF to 80oF.
Find the net power of the cycle (Btu/hr), the
thermal efficiency (%), and the mass flow rate of
the cooling water (lbm/hr).
Mollier diagram
h vs s
 Isentropic turbine operation
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Isentropic efficiency
Rankine cycle
 Into turbine: 10MPa & 580oC
 Condenser: 6kPa
 Isentropic efficiencies
• Turbine – 85%
• Pump – 82%
 Find thermal efficiency
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Innovators
Steam engine efficiency – William Rankine
 Steam engine rotary motion – James Watt
 Steam turbine – Charles Parsons
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Reheat
Rankine cycle: ideal
 Add reheat station
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amics 6E / Fig08_07
16 | 17 | 18 | 19 | 20 | 21 | 22 | 23 | 24 | 25 | 26 | 27 | 28 | 29 | 30 | 31 | 32 | 33
Regeneration
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Open feed water heater
Closed feed water heater
Indirect heating
 More complex
 More expensive
 Lower heat transfer rate
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Closed feed water heater
Feed forward
 Feed back - trap
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