Triple point measurements for alternative refrigerants

Triple point data are important in the refrigerating industry, defining the lowest temperature limit at which a refrigerant may circulate in a fluid state. For several refrigerants, triple point data present in the literature are extremely scarce or inaccurate. A recently developed Solid–Liquid Equilibria (SLE) apparatus was used to measure the triple point temperature of 16 of the most widely applied alternative refrigerants, namely three methane derivatives (fluoromethane, R41; difluoromethane, R32; trifluoromethane, R23), four ethane derivatives (pentafluoroethane, R125; 1,1,1,2-tetrafluoroethane, R134a; 1,1,1-trifluoroethane, R143a; 1,1-difluoroethane, R152a), five propane derivatives [1,1,1,2,3,3,3-heptafluoropropane, R227ea; 1,1,2,3,3,3-hexafluoropropane, R236ea; 1,1,1,3,3-Pentafluoropropane, R245fa; 1,1,2,2,3-pentafluoropropane, R245ca; 1,1,1,3,3,3-hexafluoropropane, R236fa), and four hydrofluoro-olefines (2,3,3,3-tetrafluoroprop-1-ene, R1234yf; trans-1,3,3,3 tetrafluoropropene, R1234ze(E); 3,3,3-trifluoropropene, R1243zf; 1,2,3,3,3-pentafluoropropene, 1225ye(Z)]. The experimental setup, that was recently adopted for the SLE estimation of binary systems containing carbon dioxide (J Therm Anal Calorim 105:489–493, 2011), comprises a measuring cell and a system for drawing the liquid nitrogen directly from its insulated tank with the aid of compressed air: the carrier fluid circulating in the circuit is thus the refrigerant itself. The measurements were performed both in the heating and in the cooling mode. In order to confirm the functional efficiency and fine adjustment of the apparatus, the already available triple point literature data for carbon dioxide, dimethyl ether, and nitrous oxide were also compared with the ones measured by the present setup, confirming the validity of the setup. The measured triple point data for the refrigerants revealed generally good agreement with the literature, excepting a few fluids that revealed some discrepancies.