Thermodynamic properties of 3,3,3-trifluoropropene (R1243zf): equation of state and standard reference data

The article discusses the potential use of 3,3,3-trifluoropropene (R1243zf), a new refrigerant with zero ozone-depleting potential and a very low (0.29) global warming potential. In recent years, reliable experimental information has been obtained on the thermodynamic properties (density, pressure, isochoric heat capacity, and speed of sound) of R1243zf both in the single-phase region and on the liquid-vapor saturation line. Using the values of these thermodynamic quantities obtained over a wide range of state parameters, a series of equations of state for this refrigerant have been developed. In contrast to the known equations of state, a unified fundamental equation of state is proposed in this study. The unified fundamental equation of state for R1243zf is developed within the framework of a large-scale theory of critical phenomena and the similarity relation, which makes it possible to obtain reliable data on the equilibrium properties of liquid and gas not only in the regular part of the thermodynamic surface, but also in the asymptotic neighborhood of the critical point. A unified fundamental equation of state was used to calculate the standard reference data, including information on the density, pressure, enthalpy, entropy, speed of sound, isobaric and isochoric heat capacity of 3,3,3-trifl uoropropene in the range of state parameters of 169–420 K and up to 40 MPa. To estimate the uncertainty of the standard reference data, two methods based on the calculation of various statistical characteristics were used. The expanded uncertainties of the following equilibrium properties of R1243zf were obtained: density (0.25 %); pressure (0.35 %); specific heat capacity (1.2 %); speed of sound (0.37 %); saturated vapor and liquid density (0.55 and 0.40 %, respectively). The calculated estimates of the statistical characteristics indicate that the unified fundamental equation of state adequately conveys the equilibrium properties of the refrigerant R1243zf in the above-mentioned range of state parameters. The results of the study can be used in the design of air conditioning and refrigeration systems.