A recirculation apparatus for vapor-liquid equilibrium measurements of refrigerants. Binary mixtures of R600a, R134a and R236fa

An apparatus for the measurement of vapor-liquid equilibria (P-T-x-y) data of refrigerant systems was designed, built and tested. The recirculation method was used and the vapor phase was forced through the liquid phase by a magnetic pump. The thermodynamic equilibrium was reached in a visual cell with an internal volume of 50 cm(3). The compositions of the phases were analyzed by a gas chromatograph connected on-line with either FID or TCD detectors. The operating temperature and pressure in the apparatus, as tested before delivery to the laboratory [R. Stryjek, personal communication], range from 240 to 350 K and from 0.1 to 10 MPa, respectively. The estimated accuracy of the measured data was +/-0.01 K for temperature, +/-0.8 kPa for pressure and 0.001 in mole fraction for liquid and vapor compositions. Vapor-liquid equilibria data were obtained for the following systems: 1,1,1,2-tetrafluorethane + isobutane (R134a + R600a) at 293.66 and 303.68 K; 1,1,1,2-tetrafluorethane + 1,1,1,3,3,3-hexafluoropropane (R134a + R236fa) at 283.62 and 303.68 K; and isobutane + 1,1,1,3,3,3-hexafluoropropane (R600a + R236fa) at 303.68 K. The thermodynamic consistency of the experimental results was tested.