Mapping of the Temperature–Entropy Diagrams of van der Waals Fluids

Attila R. Imre, Réka Kustán and Axel Groniewsky
Additional contact information
Attila R. Imre: Department of Energy Engineering, Faculty of Mechanical Engineering, Budapest University of Technology and Economics, Műegyetem rkp. 3, H-1111 Budapest, Hungary
Réka Kustán: Department of Thermohydraulics, Centre for Energy Research, POB. 49, H-1525 Budapest, Hungary
Axel Groniewsky: Department of Thermohydraulics, Centre for Energy Research, POB. 49, H-1525 Budapest, Hungary

Energies, 2020, vol. 13, issue 6, 1-15

Abstract: The shape of the temperature vs. specific entropy diagram of a working fluid is very important to understanding the behavior of fluid during the expansion phase of the organic Rankine cycle or similar processes. Traditional wet-dry-isentropic classifications of these materials are not sufficient; several materials remain unclassified or misclassified, while materials listed in the same class might show crucial differences. A novel classification, based on the characteristic points of the T–s diagrams was introduced recently, listing eight different classes. In this paper, we present a map of these classes for a model material, namely, the van der Waals fluid in reduced temperature (i.e., reduced molecular degree of freedom) space; the latter quantity is related to the molar isochoric specific heat. Although van der Waals fluid cannot be used to predict material properties quantitatively, the model gives a very good and proper qualitative description. Using this map, some peculiarities related to T – s diagrams of working fluids can be understood.

Keywords: adiabatic expansion; T – s diagram; working fluid classification; molecular degree of freedom (search for similar items in EconPapers)
JEL-codes: Q Q0 Q4 Q40 Q41 Q42 Q43 Q47 Q48 Q49 (search for similar items in EconPapers)
Date: 2020
References: View references in EconPapers View complete reference list from CitEc
Citations: View citations in EconPapers (4)

Downloads: (external link)
https://www.mdpi.com/1996-1073/13/6/1519/pdf (application/pdf)
https://www.mdpi.com/1996-1073/13/6/1519/ (text/html)

Related works:
This item may be available elsewhere in EconPapers: Search for items with the same title.

Export reference: BibTeX RIS (EndNote, ProCite, RefMan) HTML/Text

Persistent link: https://EconPapers.repec.org/RePEc:gam:jeners:v:13:y:2020:i:6:p:1519-:d:336055

Access Statistics for this article

Energies is currently edited by Ms. Agatha Cao

More articles in Energies from MDPI
Bibliographic data for series maintained by MDPI Indexing Manager ().