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 cm3. 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.