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Research On Thermophysical Properties Of Trifluoroiodomethane And Difluoromethane

Posted on:1999-11-29Degree:DoctorType:Dissertation
Country:ChinaCandidate:Y Y DuanFull Text:PDF
GTID:1101360062475819Subject:Engineering Thermal Physics
Abstract/Summary:PDF Full Text Request
According to the revisions of the Montreal Protocol, CFCs and HCFCs will be phased out. Trifluoroiodomethane (CF3I) is considered as a promising refrigerant, especially as an important component of mixtures, to replace CFC-12, while the available data of its thermophysical properties are very limited. Difluoromethane (CH2F2, H7FC-32) is considered as the most important alternative to HCFC-22, by mixing with other HFCs. The research on thermophysical properties of CF3I and HFC- 32, including accurate experiments of thermophysical properties and theoretical analyses, are introduced in this dissertation. The pressure measurement and control system in PVT measurement apparatus was improved. The vapor pressure of CF3I was measured with temperature ranging from below the normal boiling point to the critical point, and a vapor pressure equation of CF3I was developed, then the normal boiling point and Pitzer factor of CF3I were determined. The principle of Burnettllsochoric method for PVT measurement was discussed and a new data process method derived from thermodynamic theory was put forward. The gaseous PVT properties of CF3I were measured, and on the basis of the experiment, a gaseous equation of state for CF3I was developed. A new apparatus for critical parameters and saturated-density measurement was developed. The vapor-liquid uexisLeitce iuive of CF3I was measured by a visual observation of the meniscus. Not only the level where the meniscus disappeared but also the intensity of the critical opalescence were considered for the determination of the critical temperature and the critical density of CF3I. The correlation of saturated- density in critical region was developed and the exponent of the power law, /3, was determined. The correlations of saturated vapor and liquid densities and enthalpy- vaporization for CF3I were also developed. A new measurement method of capillary viscometer for saturated liquid viscosity measurement was developed. The methods of determining viscometer parameters and calibrating viscometer constants were discussed. The saturated liquid viscosity of CF3I was measured and was correlated as a function of temperature. A transient hot-wire instrument with two hot-wires for measuring thermal conductivity of fluids was improved so that it could be used in the whole range of gaseous phase. A new data acquisition system was also developed. The thermal conductivity of N2 was measured to test the precision of the instrument. The conductivity of gaseous CF3I was measured, and the experimental data were correlated as a function of temperature and density. The values of thermal conductivities of dilute gas and saturated vapor were obtained by extrapolation. The speed of sound measurement apparatus was improved to extend the measuring range and minimize the error in ideal-gas heat capacity determination. Based on the theory of acoustics and thermodynamics, the corrected formulas for diffraction and guided mode dispersion, Kirchhoff-Helmholtz absorption and classical absorption dispersion and vibrational relaxation dispersion, were derived. The speeds of sound of gaseous HFC-32 and CF3I were measured, and then the ideal-gas heat capacities and second acoustic virial coefficients were calculated. The correlations of second virial coefficient for IEJFC-32 and for CF3I were obtained by a semi-empirical method using the square-well potential for the intermolecular force and were compared with results based on PVT measurements.
Keywords/Search Tags:Thermodynamic properties, Transport properties, Refrigerant alternatives, Trifluoroiodomethane, Difiuoromethane
PDF Full Text Request
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