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Questions and Answers
What is the primary working fluid in the Rankine cycle used in steam power plants?
How does increasing burner operating pressure affect the Brayton cycle?
Which of the following is a component commonly used to improve the basic Brayton cycle?
What does the term 'back work ratio' refer to in the context of the Rankine cycle?
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What significant energy loss was noted from power plants in the U.S. in 1997?
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What percentage of waste heat is produced by a combined cycle power plant?
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Which type of power plant is specifically designed to utilize waste heat for heating applications?
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What is the main advantage of combined heat and power (CHP) systems?
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How much electricity output does a basic coal-fired power plant produce compared to a combined heat and power (CHP) system?
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What is the efficiency of the Rankine cycle in a steam power plant as indicated in the content?
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Why is it important for heat transfer applications to be co-located with the power source in CHP systems?
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Which of the following statements best describes the term 'cogeneration'?
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What is a key feature of heat exchangers used in CHP systems?
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Study Notes
Rankine Cycle
- The Rankine cycle is used in steam power plants.
- The working fluid is water or steam.
- The boiler/steam heater is a critical component, transferring heat from the energy carrier to the working fluid.
Brayton Cycle
- The Brayton cycle is used in gas turbine power plants.
- Air is the working fluid.
- Cycle efficiency increases with higher burner operating pressure.
- Compressor work is a significantly higher fraction of turbine work compared to a Rankine cycle.
Improving the Brayton Cycle
- Multi-stage compression with intercooling
- Multi-stage expansion with reheat
- A regenerator (counterflow heat exchanger)
- With infinite intercooling/reheat, the Brayton cycle approaches isothermal heat addition and removal.
Combined Cycle Power Plants
- Combined cycle plants recover the waste heat from the Brayton cycle using a Rankine cycle.
- This helps increase overall efficiency.
- In 1997, over 20% of the total US energy use was wasted in thermal losses from power plants - equivalent to the energy needs of the entire transportation sector.
- Combined cycle plants achieve higher efficiency than traditional steam power plants alone.
Combined Heat and Power (CHP)
- Also known as cogeneration plants.
- CHP plants utilize the heat produced during power generation as a desired product.
- CHP applications range from industrial power plants to internal combustion engines and fuel cells.
- The heat source must be co-located with the power source due to significant heat loss over long distances.
- CHP can achieve significant energy savings compared to independent heat and power generation.
Comparing CHP with Independent Generation
- CHP using natural gas or steam turbines can achieve energy savings of 31% compared to independent generation.
- CHP uses heat exchangers with high efficiencies (80-90%).
- CHP offers on-site electricity generation and waste heat recovery for heating, cooling, air conditioning, and process applications.
- CHP provides power and heat from a single fuel source.
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Description
Test your knowledge on critical concepts related to the Rankine and Brayton cycles and their applications in power plants. This quiz also explores methods for improving cycle efficiency and the advantages of combined cycle power plants. Perfect for students of thermodynamics and energy systems.
