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Exergy Efficiency of Closed and Unsteady-Flow Systems
Yunus A Çengel1, Mehmet Kanoğlu2
1Department of Mechanical Engineering, University of Nevada, Reno, NV 89557, USA.
Entropy (Basel, Switzerland)
|September 27, 2025
Summary
This study develops general exergy efficiency relations for closed and unsteady-flow systems, advancing thermodynamic analysis beyond steady-state applications. It also questions the practicality of "exergy loss" and discusses definition limitations.
Area of Science:
- Thermodynamics
- Energy Systems Analysis
Background:
- Exergy efficiency quantifies thermodynamic perfection, measuring proximity to reversible operation.
- Common exergy efficiency definitions are primarily for steady-flow systems.
- Existing definitions require broad interpretation for closed and unsteady-flow systems.
Purpose of the Study:
- Develop general exergy efficiency relations for closed and unsteady-flow systems.
- Demonstrate the application of these new relations.
- Critically evaluate the term 'exergy loss' and definition limitations.
Main Methods:
- Formulation of generalized exergy efficiency equations.
- Application of these equations to specific case studies.
- Theoretical discussion on exergy loss and efficiency definitions.
Main Results:
- Established exergy efficiency relations applicable to both closed and unsteady-flow systems.
- Demonstrated practical utility through example applications.
- Identified limitations and questioned the practical use of 'exergy loss'.
Conclusions:
- The developed relations extend exergy analysis to transient and non-flow systems.
- The study highlights the need for careful consideration of exergy loss and definition scope.
- Provides a more comprehensive framework for thermodynamic performance evaluation.
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