The Influence of Adsorption on PVT Measurements in the Gaseous Phase
Source: International Journal of Thermophysics, Volume 20, Number 6, November 1999 , pp. 1711-1719(9)
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.
Document Type: Research Article
Affiliations: 1: E. I. du Pont de Nemours & Company, Inc., Wilmington, Delaware 19898, U.S.A. Present address: Chemical Engineering Department, North Carolina State University, Box 7905, Raleigh, North Carolina 27695, U.S.A. 2: State Academy of Refrigeration, Odessa 270100, Ukraine 3: E. I. du Pont de Nemours & Company, Inc., Wilmington, Delaware 19898, U.S.A.
Publication date: 1999-11-01