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REVERSIBLE CYCLES. The Carnot Cycle. Power cycles. What is W cycle ?. Example - A consequence of K-P. Assumptions: Reversible power cycle. Reservoir at a constant temperature, T H. Example - A consequence of K-P. Example - A consequence of K-P. Analysis
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REVERSIBLE CYCLES The Carnot Cycle
What is Wcycle? Example - A consequence of K-P
Assumptions: Reversible power cycle. Reservoir at a constant temperature, TH. Example - A consequence of K-P
Example - A consequence of K-P • Analysis • According to K-P statement, Wcycle< 0. • As the cycle is reversible, it is possible to return both the system and surroundings to their initial states.
Example - A consequence of K-P • Conclusion • Thus there would be no net change in the condition of the reservoir or the elevations of the mass used to store energy in the surroundings. This is be true if and only if WCycle = 0.
Reversible cyclic heat engine A reversible power cycle is one comprising a sequence of reversible processes.
Surroundings Local Surroundings System Energetic inter- actions with the local surroundings, i.e., heat and work. The generalization of the cyclic heat engine...
What is the best performance that one expect from a cyclic heat engine operating between two thermal reservoirs? Performance of power cycles
Is there a specific design that will give us the “best possible” cyclic engine? Performance of power cycles
Performance of power cycles and the Second Law • The Second Law mandates two thermal reservoirs. • The Second Law mandates a temperature difference in order to operate the cycle. • Applies to work producing and work consuming cycles.
First Law efficiency for work producing cycles. Performance of power cycles
Performance of power cycles • Coefficient of performance for working consuming cycles.
The Carnot cycle… A fully reversible power cycle
A reversible, constant temperature (isothermal), heat addition from a high temperature reservoir. An reversible, adiabatic expansion. Processes of the Carnot cycle...
A reversible, constant temperature (isothermal) heat rejection to a low temperature reservoir. An reversible, adiabatic compression to the original state. Processes of the Carnot cycle...
Reversible heat addition at TH = Const. p Reversible work transfer, Q = 0 Reversible work transfer, Q = 0 Reversible heat Rejection at TC = Const. V The Carnot Cycle
The Carnot Cycle is a fully reversible cycle. Each process is itself reversible. The Carnot cycle
The Carnot cycle • Can be either a work producing cycle or a work consuming cycle. • Can be operated in either direction.
The Carnot cycle • Represents an idealization of most power cycles (work producing and work consuming). • Because of its reversibility and generality.
Carnot cycle Reversible isothermal process Reversible adiabatic process Reversible cycle Key concepts and terms