Vapor–liquid equilibria of novel chemicals and their mixtures as R-22 alternatives

Abstract

Vapor–liquid equilibrium (VLE) vapor pressures are reported for binary mixtures; octafluoromethylethylether+1,1-difluoroethane (RE218/R152a), trifluoromethylpentafluorosulfur(VI)+1,1-difluoroethane (CF 3SF 5/R152a), hexafluorodimethylthioether+1,1,1,2-tetrafluoroethane (CF 3SCF 3/R134a), and pentafluorodimethylether+1,1,1-trifluorodimethylether (RE125/RE143a). The mixtures; (RE218/R152a), (CF 3SF 5/R152a), and (CF 3SCF 3/R134a) form minimum boiling azeotropes with the normal boiling points; 237.9 K (−35.3°C), 239.7 K (−33.5°C), and 243.0 K (−30.2°C), respectively, and gas–liquid critical temperatures of 353.3 K (80.1°C), 365.7 K (92.5°C) and 368.2 K (95.0°C), respectively. The azeotropic mixtures have sufficiently low boiling points to serve as alternatives for the refrigerant R-22 (CHF 2Cl). The mole fractions of the perfluorinated component of these mixtures at the azeotropic compositions are 0.49, 0.41, and 0.46, respectively. The estimated critical mixing temperatures for liquid–liquid phase separation are 236 K (−37°C), 221 K (−52°C), and 341 K (−68°C), respectively, and are well below the corresponding boiling points. The ether mixtures, (RE125/RE143a), exhibit nearly ideal mixing behavior which contrasts the VLE behavior of mixtures of perfluorinated ether, RE218, with RE143a [I. Kul, D.D. DesMarteau, A.L. Beyerlein, ASHRAE Trans. 106 (1) (1999)]. In addition to binary mixtures, VLE data are reported on four ternary mixtures; RE125(33%)/R134a(33%)/R161(34%), RE125(33%)/RE143a(33%)/R161(34%), RE218(33%)/RE143a(33%)/R161(33%), and RE218(40%)/RE143a(40%)/R161(20%) with boiling points 240.6 K (−32.6°C), 241.6 K (−31.6°C), 236.7 K (−36.5°C), and 238.6 K (−34.6°C), respectively. The boiling points of the ternary mixtures are sufficiently low for a R-22 alternative.