2300_les15 - V. The Second Law of Thermodynamics E. The...

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1 lesson 15 V. The Second Law of Thermodynamics E. The Carnot Cycle 1. The reversible heat engine (a piston cylinder device) that operates on a cycle between heat reservoirs at T H and T L , as shown below on a P-v diagram, is the Carnot cycle . 2. Because the cycle is reversible, the Carnot cycle, operating between T H and T L , is the most efficient cycle possible. We want to know how much heat, Q L , must be rejected by the engine . 3. If the Carnot heat engine is operated in reverse, we call it a Carnot refrigeration cycle . •1-2 rev., isothermal expansion •2-3 rev., adiabatic expansion •3-4 rev., isothermal compression •4-1 rev., adiabatic compression T H = constant T L = constant Q H Q L 1 2 3 4 W net,out = shaded area Q 41 =0 Q 23 =0 P v H L in out th Q Q 1 Q Q 1 = = η lesson 15 V. The Second Law of Thermodynamics F. The Carnot Principles 1. “The efficiency of an irreversible heat engine is always less than the efficiency of a reversible one operating between the same two reservoirs.” (p. 302) 2. “The efficiencies of all reversible heat engines operating between the same two reservoirs are the same.” (p. 302)
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2300_les15 - V. The Second Law of Thermodynamics E. The...

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