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Exergy
In thermodynamics, exergy, symbol Ξ or B, is the maximum work done by a system during a transformation which brings it into equilibrium with a reservoir. [1] Exergy, by convention, is positive when putting the system into equilibrium with the reservoir results in doing work on the surroundings. Synonyms include “available energy”, “available work”, among others. [2] The term exergy is used predominately in ecology, economics, and branches of mechanical engineering; often presented as a simplified or verbalized version of the free energy alternative as used in the chemical-physical sciences.
Etymology
The term exergy was coined by Slovene mechanical engineer Zoran Rant in 1956, to denote “technical working capacity” or “technical available energy”; soon thereafter becoming very popular. [3] The concept of exergy or maximal work, however, as introduced by Rant, is a redressing of earlier works, in particular: American engineer Willard Gibbs (“available energy of the body and medium”, 1873), German physicist Hermann Helmholtz (“free energy”, 1882), and French physicist Louis Gouy (“possibility of obtaining work”, 1889), among other variants. [4]
Gouy-Stodola theorem
A folk theorem attributed independently to Gouy, in 1889, and Slovak mechanical engineer Aurel Stodola, in 1910, called the Gouy-Stodola theorem or the “Law of Gouy and Stodola”, states that the entropy production is the exergy loss divided by the temperature of the surroundings; thus minimizing loss of exergy is equivalent to minimizing entropy production. In equation form, this theorem reads:
where Blost denotes the potential work or exergy lost by the system in a transformation process, To denotes the temperature of the system’s surroundings, and Sgen is the entropy generated in the transformation. [2]
References
1. Perrot, Pierre. (1998). A to Z of Thermodynamics, Oxford: Oxford University Press.
2. Baumgärtner, Stefan, faber, Malte M., and Schiller, Johannes. (2006). Joint Production and Responsibility in Ecological Economics, (section: Engineering Thermodynamics: The Exergy Concept, pgs. 54-55). Edward Elgar Publishing.
3. (a) Rant, Zoran. (1956). "Exergie, ein neues Wort fur "Technische Arbeitsfahigkeit" (Exergy, a new word for "technical available work")". Forschung auf dem Gebiete des Ingenieurwesens, 22: 36–37.
(b) On Exergetics, Economics and Desalination – by Goran Wall and Mei Gong.
(c) Wall, Goran. (1986). “Exergy: a Useful Concept”, PhD thesis, Chalmers University of Technology, Goteborg.
4. (a) Gibbs, J. Willard. (1873). "A Method of Geometrical Representation of the Thermodynamic Properties of Substances by Means of Surfaces" (pgs. 49-50), Transactions of the Connecticut Academy, II. pp.382-404, Dec.
(b) Gouy, Louis G. (1889), "Sur L'Energie Utilizable" (On Utilizable Energy), Journal de Physique 8, 501.
5. Stodola, A. (1910), Steam and Gas Turbines, McGraw-Hill.
Further reading
● Demirel, Y. (2004). “Exergy use in Bioenergetics”, (Abstract), International Journal of Exergy, Vol. 1, No. 1, (pgs. 128-46).
● Wall, Goran. (1995). “Exergy and Morals: Second Law Analysis of Energy Systems: Towards the 21st Century, eds. E. Sciubba and M.J. Moran, July 5-7, Rome: Esagrafica-Roma., pgs. 21-29.
● Wall, Goran. (1997). “Energy, Society and Morals”, Journal of Human Values, Vol. 3, No. 2, (pgs. 193-206).
● Sato, Norio. (2004). Chemical Energy and Exergy: An Introduction to Chemical Thermodynamics for Engineers, (pg. 99). Elsevier.
Etymology
The term exergy was coined by Slovene mechanical engineer Zoran Rant in 1956, to denote “technical working capacity” or “technical available energy”; soon thereafter becoming very popular. [3] The concept of exergy or maximal work, however, as introduced by Rant, is a redressing of earlier works, in particular: American engineer Willard Gibbs (“available energy of the body and medium”, 1873), German physicist Hermann Helmholtz (“free energy”, 1882), and French physicist Louis Gouy (“possibility of obtaining work”, 1889), among other variants. [4]
Gouy-Stodola theorem
A folk theorem attributed independently to Gouy, in 1889, and Slovak mechanical engineer Aurel Stodola, in 1910, called the Gouy-Stodola theorem or the “Law of Gouy and Stodola”, states that the entropy production is the exergy loss divided by the temperature of the surroundings; thus minimizing loss of exergy is equivalent to minimizing entropy production. In equation form, this theorem reads:
Blost = ToSgen
where Blost denotes the potential work or exergy lost by the system in a transformation process, To denotes the temperature of the system’s surroundings, and Sgen is the entropy generated in the transformation. [2]
References
1. Perrot, Pierre. (1998). A to Z of Thermodynamics, Oxford: Oxford University Press.
2. Baumgärtner, Stefan, faber, Malte M., and Schiller, Johannes. (2006). Joint Production and Responsibility in Ecological Economics, (section: Engineering Thermodynamics: The Exergy Concept, pgs. 54-55). Edward Elgar Publishing.
3. (a) Rant, Zoran. (1956). "Exergie, ein neues Wort fur "Technische Arbeitsfahigkeit" (Exergy, a new word for "technical available work")". Forschung auf dem Gebiete des Ingenieurwesens, 22: 36–37.
(b) On Exergetics, Economics and Desalination – by Goran Wall and Mei Gong.
(c) Wall, Goran. (1986). “Exergy: a Useful Concept”, PhD thesis, Chalmers University of Technology, Goteborg.
4. (a) Gibbs, J. Willard. (1873). "A Method of Geometrical Representation of the Thermodynamic Properties of Substances by Means of Surfaces" (pgs. 49-50), Transactions of the Connecticut Academy, II. pp.382-404, Dec.
(b) Gouy, Louis G. (1889), "Sur L'Energie Utilizable" (On Utilizable Energy), Journal de Physique 8, 501.
5. Stodola, A. (1910), Steam and Gas Turbines, McGraw-Hill.
Further reading
● Demirel, Y. (2004). “Exergy use in Bioenergetics”, (Abstract), International Journal of Exergy, Vol. 1, No. 1, (pgs. 128-46).
● Wall, Goran. (1995). “Exergy and Morals: Second Law Analysis of Energy Systems: Towards the 21st Century, eds. E. Sciubba and M.J. Moran, July 5-7, Rome: Esagrafica-Roma., pgs. 21-29.
● Wall, Goran. (1997). “Energy, Society and Morals”, Journal of Human Values, Vol. 3, No. 2, (pgs. 193-206).
● Sato, Norio. (2004). Chemical Energy and Exergy: An Introduction to Chemical Thermodynamics for Engineers, (pg. 99). Elsevier.
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