Efficiency of heat pump and refrigerator

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SUMMARY

The discussion centers on the efficiency formulas for heat pumps and refrigerators, specifically e <= Tmax/(Tmax-Tmin) for heat pumps and e <= Tmin/(Tmax-Tmin) for refrigerators. Participants express confusion regarding the implications of efficiencies exceeding 1, clarifying that this is possible due to the nature of heat transfer rather than direct energy conversion. The conversation distinguishes between the Coefficient of Performance (COP) of heat pumps and the efficiency of heat engines, emphasizing that they are not equivalent concepts.

PREREQUISITES
  • Understanding of thermodynamic principles, specifically heat transfer.
  • Familiarity with the concepts of Coefficient of Performance (COP).
  • Knowledge of temperature scales and their application in thermodynamic formulas.
  • Basic comprehension of heat engines and refrigeration cycles.
NEXT STEPS
  • Research the Coefficient of Performance (COP) in detail, including its applications in HVAC systems.
  • Study the principles of thermodynamics, focusing on the laws governing heat engines and refrigeration cycles.
  • Explore real-world applications of heat pumps and refrigerators to understand their efficiencies in practical scenarios.
  • Investigate the differences between thermal efficiency and mechanical efficiency in energy systems.
USEFUL FOR

Engineers, HVAC professionals, and students studying thermodynamics who seek to deepen their understanding of heat pump and refrigerator efficiencies.

anizet
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I know the formulas for efficiencies e of heat pump (it is e<=Tmax/(Tmax-Tmin)) and refrigerator (e<=Tmin/(Tmax-Tmin)), where Tmax and Tmin are temperatures of warmer and colder (respectively) involved containers. These formulas make me puzzled, as efficiencies seem to be possibly bigger than 1. Is that correct? If yes, what does it mean?
 
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anizet said:
I know the formulas for efficiencies e of heat pump (it is e<=Tmax/(Tmax-Tmin)) and refrigerator (e<=Tmin/(Tmax-Tmin)), where Tmax and Tmin are temperatures of warmer and colder (respectively) involved containers. These formulas make me puzzled, as efficiencies seem to be possibly bigger than 1. Is that correct? If yes, what does it mean?

The http://en.wikipedia.org/wiki/Coefficient_of_performance" of a heat engine with COP. They are not the same thing.

CS
 
Last edited by a moderator:
In a typical heat engine, you have a certain amount of thermal energy that is converted to mechanical energy. In a heat pump or refrigeration cycle, the working fluid is being circulated to move heat between a hot and cold well. There is no direct corellation between the energy required to circulate the working fluid and the energy it is carrying with it when you move it.
 

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