Specifics of using NIST REFPROP program for calculating thermophysical properties of water in critical point

Any heat transfer or thermodynamics calculations as well as many other calculations require a solid knowledge of various physical/thermophysical/thermodynamics properties of various fluids (liquids, vapours, and gases) within a wide range of pressures and temperatures from lower ones and up to critical and supercritical ones. For tens of years, the NIST REFPROP program is used for these calculations, which can be possibly considered as the best one in the world. Time from time this program is updated with new fluids, or/and a wider range of pressures and temperatures, or/and with improved equations/correlations. Just two years ago, i.e., in 2018, the latest version was released – Ver. 10.0. This version includes 147 pure fluids, 5 pseudo-pure fluids (e.g., air, etc.), and mixtures with up to 20 components. The most complicated properties calculations are in the critical point, where all thermophysical properties are subjected to very significant variations, i.e., almost vertical drops or rises or have peaking functions. In the previous version(s) of the NIST REFPROP 9.1 and higher, three basic thermophysical properties such as specific heat, thermal conductivity, and volumetric expansivity have infinite peak values in the critical point, which was a theoretical approach. Therefore, the objective of the current paper is to check if these deficiencies have been fixed, because in nuclear engineering as well as other areas only a conservative approach can be used, i.e., all peak values should be the minimum possible ones. (author)