Isentropic exponents of real gases and application for the air at temperatures from 150 K to 450 K

Kouremenos, DA; Antonopoulos, KA

dc.contributor.author	Kouremenos, DA	en
dc.contributor.author	Antonopoulos, KA	en
dc.date.accessioned	2014-03-01T01:06:54Z
dc.date.available	2014-03-01T01:06:54Z
dc.date.issued	1987	en
dc.identifier.issn	0001-5970	en
dc.identifier.uri	https://dspace.lib.ntua.gr/xmlui/handle/123456789/9662
dc.subject	Fluid Mechanics	en
dc.subject	Heat Transfer	en
dc.subject	High Pressure	en
dc.subject	Internal Combustion Engine	en
dc.subject	Low Temperature	en
dc.subject	Thermodynamics	en
dc.subject.classification	Mechanics	en
dc.subject.other	FLUID MECHANICS	en
dc.subject.other	BLOWBY RATE CALCULATION	en
dc.subject.other	IDEAL GAS ISENTROPIC CHANGE EQUATIONS	en
dc.subject.other	REAL GAS ISENTROPIC EXPONENTS	en
dc.subject.other	GASES	en
dc.title	Isentropic exponents of real gases and application for the air at temperatures from 150 K to 450 K	en
heal.type	journalArticle	en
heal.identifier.primary	10.1007/BF01176874	en
heal.identifier.secondary	http://dx.doi.org/10.1007/BF01176874	en
heal.language	English	en
heal.publicationDate	1987	en
heal.abstract	Three real gas isentropic exponents kTv, krv, kpT are introduced, which when used in place of the classical isentropic exponent k=cp/c in the ideal gas isentropic change equations, the latter may describe very accurately the isentropic change of real gases. The usual practice of employing exponent k may lead to considerably incorrect results even when the value of k corresponds to the correct local value of cp/cv of the real gas under examination. The numerical values of the new exponents are calculated in the case of real air for temperatures from 150 K to 450 K and pressures from 1 bar to 1000 bar. It is seen that at low temperatures and high pressures the values of the new exponents differ considerably from the values of the classical exponent k. Therefore, the error resulting by approximating, as is usually the case, the behaviour of real gases by the ideal gas isentropic change equations in a stepwise fashion with exponent k instead of the new exponents, is considerable. It follows that exponent k, which appears in various relations in thermodynamics, fluid mechanics, gasdynamics, heat transfer etc., should be suitably replaced by combinations of the three exponents. Related numerical examples, made in the case of real air, showed that the use of k leads (in the temperature and pressure ranges examined) to a 5% error in the calculation of blowby rate in internal combustion enginers, high pressure compressors or steam turbines and to a 50% error in the calculation of the isentropic expansion or compression. © 1986 Springer-Verlag.	en
heal.publisher	Springer-Verlag	en
heal.journalName	Acta Mechanica	en
dc.identifier.doi	10.1007/BF01176874	en
dc.identifier.isi	ISI:A1987G832500007	en
dc.identifier.volume	65	en
dc.identifier.issue	1-4	en
dc.identifier.spage	81	en
dc.identifier.epage	99	en