Pitfalls of Exergy Analysis
-
Petr Vágner
,
Michal Pavelka
Abstract
The well-known Gouy–Stodola theorem states that a device produces maximum useful power when working reversibly, that is with no entropy production inside the device. This statement then leads to a method of thermodynamic optimization based on entropy production minimization. Exergy destruction (difference between exergy of fuel and exhausts) is also given by entropy production inside the device. Therefore, assessing efficiency of a device by exergy analysis is also based on the Gouy–Stodola theorem. However, assumptions that had led to the Gouy–Stodola theorem are not satisfied in several optimization scenarios, e.g. non-isothermal steady-state fuel cells, where both entropy production minimization and exergy analysis should be used with caution. We demonstrate, using non-equilibrium thermodynamics, a few cases where entropy production minimization and exergy analysis should not be applied.
Funding statement: The result was developed within the CENTEM project, reg. no. CZ.1.05/2.1.00/03.0088, cofunded by the ERDF as part of the Ministry of Education, Youth and Sports OP RDI programme and, in the follow-up sustainability stage, supported through CENTEM PLUS (LO1402) by financial means from the Ministry of Education, Youth and Sports under the National Sustainability Programme I. The work was supported by Czech Science Foundation (project no. 14-18938S). The study was supported by the Charles University, project GA UK No 70515.
Acknowledgements
We are grateful to Miroslav Grmela, who supported this research. We are also grateful to Václav Klika for encouraging us and discussing the results.
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© 2017 Walter de Gruyter GmbH, Berlin/Boston
Articles in the same Issue
- Frontmatter
- Research Articles
- Energy Transport across the Thin Films Pair with Presence of Minute Vacuum Gap at Interface
- Extra Mass Flux in Fluid Mechanics
- Extended Reversible and Irreversible Thermodynamics: A Hamiltonian Approach with Application to Heat Waves
- Maximum Work of Free-Piston Stirling Engine Generators
- Thermodynamic Optimization of an Electric Circuit as a Non-steady Energy Converter
- Pitfalls of Exergy Analysis
Articles in the same Issue
- Frontmatter
- Research Articles
- Energy Transport across the Thin Films Pair with Presence of Minute Vacuum Gap at Interface
- Extra Mass Flux in Fluid Mechanics
- Extended Reversible and Irreversible Thermodynamics: A Hamiltonian Approach with Application to Heat Waves
- Maximum Work of Free-Piston Stirling Engine Generators
- Thermodynamic Optimization of an Electric Circuit as a Non-steady Energy Converter
- Pitfalls of Exergy Analysis
