GENERAL RESEARCH Experimental and Predicted Solubilities of HFC134a (1,1,1,2-Tetrafluoroethane) in Polyethers Enriqueta R. Lo ´ pez, † Ana M. Mainar, ‡ Josefa Garcı ´a, †,§ Jose ´ S. Urieta, ‡ and Josefa Ferna ´ ndez* ,† Group of Applied Thermodynamics and Surfaces (GATHERS), Aragon Institute for Engineering Research (I3A), Facultad de Ciencias, Universidad de Zaragoza, 50009 Zaragoza, Spain, Laboratorio de Propiedades Termofı ´sicas, Departamento de Fı ´sica Aplicada, Facultad de Fı ´sica, Universidad de Santiago, 15782 Santiago de Compostela, Spain, and Departamento de Fı ´sica Aplicada, Facultad de Ciencias, Universidad de Vigo, 36200 Vigo, Spain Experimental solubilities were determined for 1,1,1,2-tetrafluoroethane (HFC134a) in triethylene glycol dimethyl ether and in tetraethylene glycol dimethyl ether at 101.33 kPa refrigerant partial pressure in the low-temperature range (258.15-298.15 K). The experimental device was adapted from an apparatus commonly used to measure slightly soluble gases. Because HFC134a was highly soluble in the two polyglycols, the mole fraction of the refrigerant was calculated by the φ-γ method and the symmetrical criteria for the components. The solubilities of the refrigerant in the two solvents were very similar. The thermodynamic quantities related to the solution process were also obtained from the solubility data. The isobaric solubilities predicted by the original and Dortmund UNIFAC versions were compared with the experimental values to test the interaction parameters of Kleiber (Fluid Phase Equilib. 1995, 107, 161) and Kleiber and Axmann (Comput. Chem. Eng. 1998, 23, 63). Introduction The restrictions imposed on the use of chlorofluoro- carbons as working fluids in heat pumps and refrigera- tion systems have stimulated the search for alternative refrigerants, such as 1,1,1,2-tetrafluoroethane (HFC134a) and other hydrofluorocarbons (HFCs), methanol, and 2,2,2-trifluoroethanol. 1-3 In this context, one of the most important tasks is to find compressor lubricants com- patible with the alternative refrigerants. 4,5 This requires information about thermophysical properties of the refrigerant, lubricant and mixtures such as density, viscosity, vapor pressure, miscibility, heat of mixing, heat capacity or thermal conductivity; and solubility of the refrigerant in the lubricant. However, it has been found that the mutual miscibili- ties of conventional lubricating oils [i.e., mineral oil, poly(R-olefin), alkylbenzene, etc.] and HFC refrigerants are quite poor, thus leading to poor performances of the refrigerating devices. To avoid this, poly(alkylene glycol) (PAG), polyol ester (POE), and other new lubricants have been developed for commercial applications with HFCs and blends of HFCs with other refrigerants. 4 In recent years, experiments have been carried out using PAG-type compounds as compressor lubricants with HFC134a. 6 Some useful PAGs are poly(ethylene glycol) dimethyl ethers, CH 3 O-[(CH 2 ) 2 O] n -CH 3 , because they are thermally and chemically stable, with much higher boiling points than alternative refrigerants proposed for absorption cycles. Moreover, dimethyl ether functional groups have an advantageous strong affinity for the small polar molecules of refrigerants. Tseregounis and Riley 6 have measured the solubility of HFC134a in several glycol-type compounds (glycols and glycol derivatives), concluding that the PAG tetra- ethylene glycol dimethyl ether (TEGDME, n ) 4) shows a higher ability to dissolve HFC134a. According to these authors, this fact is the result of eliminating the free OH group from glycol compounds. Moreover, water is less soluble in the ether than in the original glycol. Recently, Coronas et al. 7 measured the vapor-liquid equilibrium (VLE) of HFC134a + triethylene glycol dimethyl ether (TrEGDME, n ) 3) in a temperature range of 283.15-353.15 K using a static method. No data have been published for HFC134a + TrEGDME or TEGDME at temperatures below 283.15 K, even though these working conditions are remark- ably important in many applications, such as absorption systems. 8 In this paper, we report the solubilities of the refrig- erant 1,1,1,2-tetrafluoroethane (HFC134a) in triethyl- ene glycol dimethyl ether and tetraethylene glycol dimethyl ether at 101.33 kPa partial pressure of gas and a range of temperatures (258.15-298.15 K). Because these solubilities are rather large, we modified and tested an existing Ben-Naim-type apparatus, 9 previ- ously used to measure slightly soluble gases in pure and mixed organic solvents. We also calculated several * To whom correspondence should be addressed. tel.: +34 981 563 100 (ext. 14046). Fax: +34 981 520 676. E-mail: fajferna@usc.es. † Universidad de Santiago de Compostela. ‡ Universidad de Zaragoza. § Universidad de Vigo. 1523 Ind. Eng. Chem. Res. 2004, 43, 1523-1529 10.1021/ie030623w CCC: $27.50 © 2004 American Chemical Society Published on Web 02/14/2004