Prediction of the volumetric and thermodynamic properties of some refrigerants using GMA equation of statePrévision des propriétés volumétriques et thermodynamiques de certains frigorigènes à l'aide d'une équation d'état Goharshadi-Morsali-Abbaspour (GMA)
Introduction
Halogenated hydrocarbons are the generic base of most refrigerants. They are known to be greenhouse gases; some of them are even suspected to have an ozone depleting potential (ODP). There are different kinds of halocarbon refrigerants such as chlorofluorocarbons (CFCs), hydrochlorofluorocarbons (HCFCs), and hydrofluorocarbons (HFCs).
Prior to the 1980s, the principal classes of chemicals used as refrigerants in the refrigeration industry were CFCs and HCFCs. CFCs consist of molecules containing only atoms of chlorine, fluorine, and carbon. HCFCs consist of molecules containing atoms of hydrogen in addition to atoms of chlorine, fluorine, and carbon. In addition to their use as refrigerants, many of the CFCs and HCFCs were used as blowing agents, fire extinguishing agents, cleaning solvents and extensively as industrial and consumer product aerosol propellants. CFCs and HCFCs were identified as effective and energy efficient refrigerants. These chemicals have many unusual properties, for example, non-flammability, low toxicity, and material compatibility that have led to their common widespread use around the world, especially as refrigerants in air conditioning and refrigerating systems [1], [2], [3].
Based on growing evidence of ozone depletion, over 100 countries adopted the Montreal Protocol (MP) of 1987, which effectively prohibited CFCs use or production after January 1, 1996. The amount of CFCs actually produced by developed countries is decreasing rapidly [4]. As a result of the limitations, which the Montreal Protocol placed on CFCs, industries worldwide turned to HCFCs as substitutes for CFCs. While HCFCs have a lower ozone depleting potential than CFCs, they still damage the ozone layer and have themselves become subject to scheduled phase out by 2030.
HFCs consist of molecules containing only atoms of hydrogen, fluorine, and carbon and were known at the time of the Montreal Protocol to have effectively zero ODP. Following the Montreal Protocol, many participants in the refrigerant manufacturing industry therefore looked towards HFCs as replacements for CFCs across a range of applications and HFCs are among the best fluids for the refrigeration industry [5]. HFCs have almost zero ODP, since they do not contain chlorine.
The purpose of this work is to report the results of simultaneous calculations of volumetric and thermodynamic properties such as isobaric expansion coefficient, α, isothermal compressibility, β, and vapor–liquid equilibrium (VLE) prediction for some HCFC and HFC refrigerants using GMA EoS [6]. A wide comparison with experimental data was made. The accuracy of the equation of state for density has been determined by the statistical parameters, namely, the absolute average deviation (AAD), the average percent deviation (bias), the root mean square deviation (RMSD), and the standard deviation (SD).
Section snippets
Theoretical basis
A general equation of state for liquids has been recently derived by Goharshadi et al. [6], “GMA EoS”, which has been found to be valid for polar, nonpolar, and hydrogen-bonded fluids. The equation of state is based on the average potential energy and that iswhere Z, Vm, and ρ are compressibility factor, molar volume, and density, respectively. The intercept and the slope of this equation both depend on temperature via the equations:and
Results
The various refrigerants studied are listed in Table 1, together with their IUPAC and ASHRAE (American Society of Heating, Refrigerating, and Air-Conditioning Engineers) names, formula, and critical temperatures. Table 2 shows the pressure and temperature ranges of the data for HCFC and HFC compounds studied. Fig. 1, Fig. 2 show isotherms of (2Z−1)Vm3 versus density for 1,1-dichloro-2,2,2-trifluoroethane and 1,1,1-trifluoroethane, respectively, for a typical temperature. As the figures show the
Conclusions
The volumetric properties and vapor–liquid equilibrium (VLE) prediction for some HCFC and HFC refrigerants have been performed using GMA EoS over a wide ranges of temperature and pressure. A wide comparison with experimental data was made. The generally excellent agreement indicates that the liquid phase thermodynamic properties of these compounds can be calculated using GMA EoS with a high degree of certainty.
The accuracy of the equation of state in the prediction of density has also been
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2013, Journal of Molecular LiquidsCitation Excerpt :The new proposed equation was named group contribution method-GMA equation (GCM-GMA equation). The GMA equation states that for most of the normal dense fluids in the range of T < TC and ρ > ρC, the isotherms of (2Z − 1)Vm3 versus ρ are linear [24,28,29]. This equation has been also applied to liquid mixtures [30–32].