PVT Properties of Water in the Critical Region

A new set of experimental PVT; property and vapor pressure data is reported for the range of temperatures 643-673 K, of pressures 20-40 MPa and of densities 108-618 kg/m3. The experimental uncertainties in the present study are estimated to be +0.04% for density, ± 4 mK for temperature, + 5kPa for pressure in the PVT measurements and +3kPa for vapor pressure data measured. Some detailed comparison of the measured results have been made not only with those reported by the previous investigators, but also with the equations of state proposed recently. The compared results have shown that the present measurements were in good agreement with an available single set of extensive measurements by Rivkin et at. for the densities below 500kg/m3, whereas the latter reported for higher densities above 500kg/m3 seemed less reliable because the present results agreed more satisfactorily with another sets of reliable data by Kell et al. and also by Alexandrov et al. Based upon the present measured vapor pressure data as well as those reported previously, an analytical vapor pressure correlation has been developed for the entire temperature range between the triple point and the critical point. At the same time, a nonanalytical scaled equation of state formulated by Hanafusa based upon the present measured results has been discussed in detail and the critical parameters of water have been recommended with evaluated uncertainties.