Recent trends in the development of Helmholtz energy equations of state and their application to 3,3,3-trifluoroprop-1-ene (R-1243zf)

Recent trends in the development of Helmholtz energy equations of state are briefly reviewed. Optimization procedures have been improved over the last two decades, and now nonlinear least-square fitting is effectively used in the optimization. This fitting technique makes it possible to develop a reliable equation of state for fluids with limited experimental data. The fitting is demonstrated for 3,3,3-trifluoroprop-1-ene (R-1243zf; CAS number 677-21-4). Experimental data for the critical parameters, vapor pressures, and liquid and vapor densities, including those at the saturation state, are available for this refrigerant. The fitting results in an equation with 17 terms. The equation of state is valid for temperatures from 234 to 376K and for pressures up to 35 MPa. Comparisons to experimental data and verification of extrapolation behavior show that the equation of state has potential for most technical applications.