Objective 02: The Carnot Cycle Flashcards
Who and when was the engine cycle that remains the model for upper limit of efficiency of heat engines proposed?
Sadi Carnot in 1824
How does the Carnot Cycle explain the operation of an ideal engine?
- All heat supplied to the engine must be at the highest temperature of the cycle
- All heat rejected must be at the lowest temperature of the cycle
- The expansion of the Working Fluid must take place without any heat transfer to or from the surroundings and without any internal loss of energy
What is the benefit of a Carnot Engine Cycle?
It produces the maximum work output of any cycle working between the same temperature limits
What are the 4 steps of the Carnot Cycle?
- Isothermal Heat Addition
- Adiabatic Expansion
- Isothermal Heat Rejection
- Adiabatic Re-Compression
What is the total supplied heat in a Carnot Cycle equal to?
The sum of the heat that is converted to work and the heat that is rejected.
Why is the Carnot Cycle more efficient than other cycles?
It suffers no losses due to radiation, conduction, or friction
What characterizes the heat addition and heat rejection in a Carnot Cycle?
Isothermal
How is the ideal efficiency of thermodynamic cycles represented?
The ratio of the net mechanical work extracted from the cycle and the heat supplied
What is the thermal efficiency of Gas Cycles that use air often also called?
Air Standard Efficiency
Why are actual values always somewhat lower than the ideal efficiency?
Friction and other heat losses results in increase in entropy so compression and expansion processes are not necessarily isentropic
Is the Carnot Cycle impractical to implement?
Yes
If the Carnot Cycle is impractical to implement, what is its value?
It conceptually has the highest possible efficiency and therefore valuable as a means of comparison
