Maximum efficiency of low-dissipation heat pumps at given heating load

Area of Science:

• Thermodynamics
• Heat Transfer
• Energy Systems Engineering

Background:

• Heat pumps are crucial for efficient heating and cooling.
• Understanding their maximum efficiency is key to energy conservation.
• Finite-time thermodynamics offers a framework for analyzing real-world cycles.

Purpose of the Study:

• To derive an analytical expression for the maximum efficiency of heat pumps operating on a finite-time reverse Carnot cycle.
• To establish upper and lower bounds for this maximum efficiency.
• To explore approximations and special cases for heat pump performance.

Main Methods:

• Derivation of an analytical expression for maximum efficiency under the low-dissipation assumption.
• Analysis of the finite-time reverse Carnot cycle for heat pumps.
• Comparison with results for endoreversible heat pumps.

Main Results:

• An analytical expression for maximum efficiency at fixed power was derived.
• Simple formulas for tight upper and lower bounds on maximum efficiency were obtained.
• A special parameter regime where low-dissipation and endoreversible heat pumps perform identically was identified.

Conclusions:

• The derived expressions provide valuable insights into heat pump performance limits.
• Results offer practical approximations for optimizing heat pump operation.
• Understanding maximum efficiency at given power aids in identifying practical operating regimes.