Improved and Always Improving: Reference Formulations for Thermophysical Properties of Water

This Review presents the state of knowledge of the thermophysical properties of water in all its phases and the reference formulations that provide standardized, recommended values of these properties for science and industry. The main focus is the standard formulations adopted by the International Association for the Properties of Water and Steam (IAPWS), but some properties are covered for which IAPWS has not yet adopted recommendations. It is emphasized that, despite many advances over the last 100 years, there is room for further improvement, and current weaknesses and opportunities for advancing knowledge are discussed. Particular attention is given to the formulation for thermodynamic properties of fluid water known as IAPWS-95, which is planned to be replaced in the coming years. Additional topics include properties of heavy water and seawater and the growing ability of molecular modeling to provide properties at conditions where experimental measurements are difficult or inaccurate.(c) 2023 by the U.S. Secretary of Commerce on behalf of the United States.