Clausius-Clapeyron equation and saturation vapour pressure: Simple theory reconciled with practice

Koutsoyiannis, D

dc.contributor.author	Koutsoyiannis, D	en
dc.date.accessioned	2014-03-01T02:08:22Z
dc.date.available	2014-03-01T02:08:22Z
dc.date.issued	2012	en
dc.identifier.issn	01430807	en
dc.identifier.uri	https://dspace.lib.ntua.gr/xmlui/handle/123456789/29649
dc.subject.other	Clausius-Clapeyron equations	en
dc.subject.other	Closed solutions	en
dc.subject.other	Entropy maximization	en
dc.subject.other	Latent heat of vaporization	en
dc.subject.other	Thermophysics	en
dc.subject.other	Vapour pressures	en
dc.subject.other	Climatology	en
dc.subject.other	Entropy	en
dc.title	Clausius-Clapeyron equation and saturation vapour pressure: Simple theory reconciled with practice	en
heal.type	journalArticle	en
heal.identifier.primary	10.1088/0143-0807/33/2/295	en
heal.identifier.secondary	http://dx.doi.org/10.1088/0143-0807/33/2/295	en
heal.publicationDate	2012	en
heal.abstract	While the Clausius-Clapeyron equation is very important as it determines the saturation vapour pressure, in practice it is replaced by empirical, typically Magnus-type, equations which are more accurate. It is shown that the reduced accuracy reflects an inconsistent assumption that the latent heat of vaporization is constant. Not only is this assumption unnecessary and excessive, but it is also contradictory to entropy maximization. There is an additional erroneous assumption for the derivation of the Clausius-Clapeyron equation, related to the equality of chemical potentials of the two phases, which does not affect the final result but puts into question the logical coherence of the equation's derivation. Removing these assumptions and using a pure entropy maximization framework we obtain a simple closed solution which is both theoretically consistent and accurate. Our discussion and derivation are relevant to students and specialists in statistical thermophysics and in geophysical sciences, and our results are ready for practical application in physics as well as in such disciplines as hydrology, meteorology and climatology. © 2012 IOP Publishing Ltd.	en
heal.journalName	European Journal of Physics	en
dc.identifier.doi	10.1088/0143-0807/33/2/295	en
dc.identifier.volume	33	en
dc.identifier.issue	2	en
dc.identifier.spage	295	en
dc.identifier.epage	305	en