Irreversibility in energy processes: non-dimensional quantification and balance


The concept of thermodynamic efficiency (ratio of real cycle efficiency by Carnot efficiency) is well-known. The concept of numbers of entropy-production and of exergy-loss proposed by A. Bejan are also known, but rarely used. The present study firstly evidences that these two last numbers are actually identical, thus being a common number of irreversibility, independent of the method used for obtaining it. The study also evidences a non-dimensional irreversibility balance that applies to any energy conversion process. This balance correlates the thermodynamic efficiency of a whole process (which in most cases equals the exergetic efficiency) and the numbers of irreversibility of the different components or sub-processes involved in this process. Moreover, the basic additivity of entropy-productions and exergy-losses is maintained in this balance. This balance applies to the basic cycles (heat-engines, refrigerators, heat-pumps and heat-transformers), either workor heat-powered. It also applies to more complex cycles (heat-powered cycles consuming electricity, four-temperature heat-powered cycles, cogeneration processes), thus giving a robust framework for analyzing these cycles

Full Text

Duke Authors

Cited Authors

  • Pons, M; Bejan, A

Published Date

  • 2004

Published In

  • J. Non-Equilib. Thermodyn. (Germany)

Volume / Issue

  • 29 / 2

Start / End Page

  • 157 - 175

Digital Object Identifier (DOI)

  • 10.1515/JNETDY.2004.010