Ideal gas relations for the description of the real gas isentropic changes

Kouremenos, DA; Kakatsios, XK

dc.contributor.author	Kouremenos, DA	en
dc.contributor.author	Kakatsios, XK	en
dc.date.accessioned	2014-03-01T01:06:25Z
dc.date.available	2014-03-01T01:06:25Z
dc.date.issued	1985	en
dc.identifier.issn	0015-7899	en
dc.identifier.uri	https://dspace.lib.ntua.gr/xmlui/handle/123456789/9370
dc.subject	Cross Sectional Area	en
dc.subject.classification	Engineering, Multidisciplinary	en
dc.subject.classification	Engineering, Mechanical	en
dc.subject.other	AIR	en
dc.subject.other	AMMONIA	en
dc.subject.other	HYDROGEN	en
dc.subject.other	REFRIGERANTS - Freons	en
dc.subject.other	IDEAL GAS RELATIONS	en
dc.subject.other	ISENTROPIC CHANGES	en
dc.subject.other	R12 REFRIGERANT	en
dc.subject.other	R22 REFRIGERANT	en
dc.subject.other	GASES	en
dc.title	Ideal gas relations for the description of the real gas isentropic changes	en
heal.type	journalArticle	en
heal.identifier.primary	10.1007/BF02561318	en
heal.identifier.secondary	http://dx.doi.org/10.1007/BF02561318	en
heal.language	English	en
heal.publicationDate	1985	en
heal.abstract	Using the best available relations describing the thermal and caloric behaviour of the media H2O, air, NH3 and of the refrigerants R12 and R22, numerous isentropic expansions starting at different initial points, have been computed. The results obtained were approximated by explicit relations having mathematical forms similar to those of the ideal gas but with different constants and exponents. The obtained accuracy is remarkable, being for the most cases better than 0.5% and in any case better than 3%. In this way the isentropic change, of the above mentioned media, can be computed by simple explicit relations having as independent variable the Mach number. Considering all the above media, the following general rules can be traced. The specific volume, reduced by the corresponding value of the stagnation point, up to a Mach number of less than 0.7, follows a parabolic law common to all gases considered. The reduced pressure, in the transonic region 0.7≦M≦1.3, has a nearly linear decrease, having a slope, common to all media, and equal to about -0.605. The reduced nozzle cross-sectional area, for M≦1,2 has a common form given by the relation F*/F=-0.034+M(2.04-M). The values of the constants and exponents used in the relations cannot be derived from the kid =Cp/Cv values since they are all the three different isentropic exponents kp,v, kT,v and kp,T involved and further since the true sound velocity α is given by the relation α=(zkp,v RT)1/2 and is not approximated by the ideal gas sound velocity αid=(kid RT)1/2. © 1985 VDI-Verlag GmbH.	en
heal.publisher	Springer-Verlag	en
heal.journalName	Forschung im Ingenieurwesen	en
dc.identifier.doi	10.1007/BF02561318	en
dc.identifier.isi	ISI:A1985AXD2100001	en
dc.identifier.volume	51	en
dc.identifier.issue	6	en
dc.identifier.spage	169	en
dc.identifier.epage	174	en