The IAPWS industrial formulation 1997 for the thermodynamic properties of water and steam

In 1997, the International Association for the Properties of Water and Stea m (IAPWS) adopted a new formulation for the thermodynamic proper-ties of wa ter and steam for industrial use. This new formulation, called IAPWS Indust rial Formulation 1997 for the Thermodynamic Properties of Water and Steam ( IAPWS-IF97), replaces the previous industrial formulation, IFC-67, that had formed the basis for power-plant calculations and other applications in en ergy engineering since the late 1960's. IAPWS-IF97 improves significantly b oth the accuracy and the speed of the calculation of the thermodynamic prop erties compared with IFC-67. The differences between IAPWS-IF97 and IFC-67 will require many users, particularly boiler and turbine manufacturers, to modify design and application codes. This paper summarizes the need and the requirements for such a new industrial formulation and gives the entire nu merical information about the individual equations of IAPWS-IF97. Moreover, the scientific basis for the development of the equations is summarized an d the achieved quality of IAPWS-IF97 is presented regarding the three crite rions accuracy, consistency along region boundaries, and computation speed. For comparison, corresponding results for the previous standard IFC-67 are also presented.