IAPWS-IF97
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| IAPWS-IF97 | |
|---|---|
| Name | IAPWS-IF97 |
| Caption | International Association for the Properties of Water and Steam formulation for industrial use |
| Developer | International Association for the Properties of Water and Steam |
| First released | 1997 |
| Latest version | 1997 (revised 2007) |
| Type | Thermodynamic property standard |
IAPWS-IF97 IAPWS-IF97 is the industrial standard for the thermodynamic properties of water and steam, promulgated by the International Association for the Properties of Water and Steam, used globally in power generation, chemical processing, and thermal engineering. It provides a consistent set of region-dependent equations and auxiliary relations enabling calculation of properties such as enthalpy, entropy, internal energy, specific volume, and saturation conditions for engineering design and legal metrology.
Overview
IAPWS-IF97 was adopted by the International Association for the Properties of Water and Steam and is referenced by standards bodies including ISO, ASME, IEC, IEEE, and DIN for steam tables and software implementations. It replaced earlier formulations such as the IAPWS-IF67 and harmonizes with thermodynamic work by contributors at institutions like NIST, PTB, NPL, VTT Technical Research Centre of Finland and industrial research groups at General Electric, Siemens, Mitsubishi Heavy Industries and Alstom. The formulation underpins commercial products and research tools produced by vendors like ANSYS, Siemens PLM Software, MathWorks, Wärtsilä, and academic codes developed at MIT, ETH Zurich, TU Delft, Imperial College London, and University of Cambridge.
Formulation and Regions
IAPWS-IF97 divides the thermodynamic surface into distinct regions: Region 1 (liquid water), Region 2 (vapor/low-density fluid), Region 3 (high-density/critical region), Region 4 (saturation curve), and Region 5 (high-temperature steam). The regional partitioning follows experimental and theoretical work affiliated with laboratories such as Argonne National Laboratory, Oak Ridge National Laboratory, Lawrence Livermore National Laboratory, and universities including University of Tokyo, Tsinghua University, University of California, Berkeley, and University of Manchester. The region boundaries reference critical parameters studied by researchers at Royal Society, Max Planck Society, and national metrology institutes like BNM-LNE and MEP China.
Equations and Backward/Forward Relations
Core expressions of IAPWS-IF97 include explicit forward equations for specific Gibbs free energy and pressure-dependent formulations together with backward relations for temperature as a function of pressure and enthalpy or entropy. These relations build on methods developed in thermodynamics by figures and institutions associated with Ludwig Boltzmann’s legacy, contemporary numerical analysis from John von Neumann schools, and applied mathematics groups at Courant Institute, Cambridge Mathematical Laboratory, Max Planck Institute for Mathematics in the Sciences, and INRIA. Backward equations (e.g., T(p,h), T(p,s)) are implemented using iterative root-finding algorithms inspired by work at Los Alamos National Laboratory and mathematical methods from SIAM-affiliated researchers. Auxiliary formulations include virial coefficients and saturation models informed by studies at Cavendish Laboratory, ETH Zurich, Columbia University, and Princeton University.
Implementation and Computational Methods
Software implementations appear in libraries and packages from Wolfram Research, MathWorks, Python Software Foundation-based projects, and open-source projects hosted by institutions like University of Oxford and University of Cambridge. Computational strategies incorporate polynomial fits, spline interpolation, and rational function approximations with coefficients derived by committees including experts from IAPWS, ASME PTC, IEC TC 27, ISO TC 112, and national standards organizations like BSI, AFNOR, and JISC. Numerical stability and speed-up techniques build on numerical linear algebra from LAPACK and optimization routines influenced by Fletcher–Reeves and Davidon–Fletcher–Powell methods, and make use of CPU and GPU acceleration architectures developed by Intel, NVIDIA, and ARM Limited. Test suites and validation harnesses are maintained by research groups at ETH Zurich, TU Wien, KTH Royal Institute of Technology, and industrial labs at Doosan Heavy Industries and Toshiba.
Applications and Industry Use
IAPWS-IF97 is critical for the design and operation of thermal power plants such as those by Siemens Energy, General Electric Power, Mitsubishi Heavy Industries, and Doosan; for steam turbine performance modeling used by companies like Alstom; and for process simulation in petrochemical complexes operated by Shell, BP, ExxonMobil, and TotalEnergies. It informs control systems developed by vendors like ABB, Schneider Electric, and Honeywell and is used in research at institutions including Lawrence Berkeley National Laboratory, Fraunhofer Society, CEA, and RMIT University. Regulatory and certification processes by agencies such as EPA, DOE, Ofgem, and grid operators in regions like European Union, United States, Japan, and China reference IAPWS-IF97 for performance claims.
Validation, Accuracy, and Limitations
Validation campaigns compare IAPWS-IF97 predictions with experimental datasets from synchrotron measurements at facilities like DESY, cryogenic and high-pressure work at CERN and Brookhaven National Laboratory, and high-precision calorimetry at NIST, PTB, and IRMM. Typical uncertainties are small in Regions 1 and 2 but increase in Region 3 near the critical point; limitations arise for supercritical mixtures, non-equilibrium steam-water flows, and multi-component systems such as mixtures encountered in Chevron and BASF processes. Extensions and complementary models (e.g., IAPWS formulations for humid air, transport properties, and dielectric constants) are handled by separate IAPWS releases and related committees involving IUPAC and IEC working groups.
History and Development of IAPWS-IF97
The development of IAPWS-IF97 was coordinated by the International Association for the Properties of Water and Steam following international meetings that involved delegations from United Nations Economic Commission for Europe, national metrology institutes, and industry representatives from Siemens, General Electric, and Alstom. The formulation consolidated decades of research by institutions such as NIST, CNR institutes in Italy, CSIR in South Africa, and academic contributors from MIT, Caltech, University of Tokyo, and University of Sydney. Revisions and technical updates have been reviewed in conferences sponsored by ASME, IIR (International Institute of Refrigeration), IChemE, and journals associated with Royal Society of Chemistry and Elsevier-published periodicals.