A Fundamental Equation of State for 1,1,1,3,3-Pentafluoropropane (R-245fa)

Abstract

A new fundamental equation of state explicit in the Helmholtz energy is presented for 1,1,1,3,3-pentafluoropropane (R-245fa), based on recent experimental data for vapor pressures, densities, and sound speeds. The functional form uses Gaussian bell-shaped terms, according to recent trends in the development of accurate equations of state. The independent variables of the equation of state are temperature and density. The equation is valid for temperatures between the triple point (170.0 K) and 440 K, and for pressures up to 200 MPa. Estimated uncertainties in this range are 0.1% for vapor pressures, 0.1% for saturated liquid densities, 0.1% for liquid densities below 70 MPa, 0.2% for densities at higher pressures, 0.3% for vapor densities, 0.3% for liquid sound speeds, and 0.1% for vapor sound speeds. The uncertainties in the critical region are higher for all properties except vapor pressures. The equation shows reasonable extrapolation behavior at extremely low and high temperatures, and at high pressures.