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Nova Odesa, Ukraine

Chernyak Y.,DuPont Company | Zhelezny V.P.,State Academy of Refrigeration | Yokozeki A.,DuPont Company
International Journal of Thermophysics | Year: 2014

PVT measurements of 1,1,1,2-tetrafluoroethane (C2H2F4, HFC-134a) and its blend with octofluoropropane (C3F8, FC-218) have been performed in the gas phase near the dew curve. The experimental data were obtained by variable-volume and vibrating tube methods. Discrepancies in the behavior of isotherms from their classical behavior were experimentally observed. It was found that the phase transition does not go to completion at a single point of the thermodynamic surface but extends over a limited range of conditions. Obtained results are in accordance with a concept of adsorption of the vapor sample on the surface of the experimental cell. An increase in adsorption under the conditions close to condensation is caused by capillary condensation of the sample at the walls of the cell that initiates an early phase transition. The ranges of diffuse phase transitions were determined for 1,1,1,2-tetrafluoroethane as well as for its mixture with octofluoropropane at different thermodynamic parameters. The influence of selective adsorption on the change in the conditions of phase transition of the 1,1,1,2-tetrafluoroethane/octofluoropropane mixture was also experimentally studied. © 1999, Plenum Publishing Corporation.

Zhelezny V.P.,State Academy of Refrigeration | Bysko E.G.,State Academy of Refrigeration
International Journal of Thermophysics | Year: 2014

The use of scaling principles for the prediction of surface tension was studied. The temperature dependences of the capillary constant, density difference on the saturation line, and surface tension were investigated. New relations containing only a few constants were proposed, which made it possible to calculate the capillary constant and surface tension. On the basis of theoretical and experimental studies, equations have been determined for the calculation of the surface tension of poorly studied refrigerants over wide regions of the state parameters. Relations are also proposed that may be used for calculating the surface tension of binary mixtures at specified compositions of the liquid phase. An equation of the surface tension for reduced isotherms was proposed. Results of investigations of the surface tension of binary mixtures, R116/23, R22/14, R134a/152a, and R22/142b, are presented. © 1999, Plenum Publishing Corporation.

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