A fundamental equation of state for cis-1,3,3,3-tetrafluoropropene (R-1234ze(Z))

• A fundamental equation of state explicit in the Helmholtz energy was developed for cis-1,3,3,3-tetrafluoropropene (R-1234ze(Z)).
• The equation covers temperatures between 273 K and 430 K for pressures up to 6 MPa.
• The estimated uncertainties are 0.2% in liquid density, 0.4% in vapor densities, and 0.15% in vapor pressures.
• The equation is fully applicable to assess heat pump cycles using R-1234ze(Z).

A fundamental equation of state is presented for cis-1,3,3,3-tetrafluoropropene (R-1234ze(Z)). The equation of state is expressed explicitly in the Helmholtz energy with independent variables of temperature and density. The equation of state is based on experimental data for the critical parameters, vapor pressures, densities of the liquid and vapor phases, and sound speeds in the vapor phase. All thermodynamic properties can be derived as derivatives of the Helmholtz energy. The equation is valid for temperatures from 273 K to 430 K and for pressures up to 6 MPa. The estimated uncertainties of properties calculated from the equation are 0.15% in vapor pressures, 0.4% in vapor densities, 0.2% in liquid densities, and 0.05% in the vapor phase sound speeds. The equation exhibits reasonable extrapolation behavior in regions away from the experimental data.