Hidden Heat Reservoirs and Violations of the 2nd Law of Thermodynamics

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SUMMARY

The discussion centers on the implications of the 2nd Law of Thermodynamics, specifically the Clausius and Kelvin-Plank statements. A scenario is presented where two thermodynamic systems interact with the same heat reservoirs, leading to a potential violation of the Kelvin-Plank statement when boundaries are redefined. The concept of hidden internal energy sources, such as heat reservoirs within a system, is introduced as a critical factor in understanding these violations. The conversation emphasizes the importance of system boundaries in thermodynamic analysis.

PREREQUISITES
  • Understanding of the 2nd Law of Thermodynamics
  • Familiarity with Clausius and Kelvin-Plank statements
  • Knowledge of thermodynamic system boundaries
  • Concept of internal energy sources in thermodynamics
NEXT STEPS
  • Study the implications of the Clausius statement on thermodynamic systems
  • Research the Kelvin-Plank statement and its applications in real-world scenarios
  • Explore the concept of hidden heat reservoirs in thermodynamic systems
  • Examine case studies involving violations of the 2nd Law of Thermodynamics
USEFUL FOR

Students of thermodynamics, physicists, and engineers interested in advanced thermodynamic principles and their applications in system design.

cmcpeek
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I have a quick question concerning the 2nd law of thermodynamics. So my textbook uses an illustration to explain how the violation of the Clausius statement of the 2nd law implies a violation of the Kelvin-Plank. But while looking over the diagram I stated thinking about a certain situation. In the diagram two systems are shown communicating thermally with the same reservoirs. The on on the left is in violation of the Clausius statement while the one on the right is thermodynamicaly sound as its own system. But when you draw the boundary line around the two cycles and the cold reservoir, it violates the Kelvin-Plank statement, which is perfectly okay. However, what if a system boundary were drawn around the cycle to the right and the cold reservoir, making a system consisting of those two entities. It would seem that the system would be communication thermally with only one reservoir (the hot one) yet generate a net output of work, which violates the Kelvin-Plank statement. Any insight would be appreciated.
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I cannot see but it sounds like you have a system with a hidden internal energy source: the heat reservoir inside the box.
It still counts.
 

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