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

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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 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

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