**IAPWS-IF97
(Basis of ES_StableIF97)**

IAPWS-IF97 is the abbreviation of "IAPWS Industrial Formulation 1997 for the Thermodynamic Properties of Water and Steam" and IAPWS is an international non-profit association of national organization with the full name of "The International Association for the Properties of Water and Steam". Please visit IAPWS web http://www.iapws.org for details of IAPWS and IAPWS-IF97.

The following is an excerption from the IAPWS web site about IAPWS-IF97.

< Quote >

"For the special requirements of the steam power industry, IAPWS also maintains a separate formulation for industrial use. In 1997, IAPWS approved a new formulation of the thermodynamic properties of water and steam for industrial use (referred to as IAPWS-IF97), replacing the IFC-67 formulation that is familiar to many from its use in the 1967 ASME Steam Tables. An archival paper describing this formulation has been published.

IAPWS recommended a conversion period in which IAPWS-IF97 should not be used as the basis of contracts; that period ended January 1, 1999."

< Unquote >

ES_StableIF97 is based on the following documents of IAPWS.

Abbreviation |
Document |
Equations |

IAPWS-IF97 |
"Revised Release on the IAPWS Industrial Formulation 1997 for the Thermodynamic Properties of Water and Steam", authorized by IAPWS at its meeting in Lucerne, Switzerland, August 2007. |
- All Basic Equations - Backward Equations of T(p,h), T(p,s) for Region 1 and 2 - Metastable-Vapor equation for Region 2 |

IAPWS-IF97-01 |
"Supplementary Release on Backward Equations for Pressure as a Function of Enthalpy and Entropy p(h,s) to the IAPWS Industrial Formulation 1997 for the Thermodynamic Properties of Water and Steam", authorized by IAPWS at its meeting in Gaithersburg, Maryland, USA, September 2001. |
- Backward Equations of p(h,s) for Region 1 and 2 |

IAPWS-IF97-03 |
"Revised Supplementary Release on Backward Equations for the Functions T(p,h), v(p,h) and T(p,s), v(p,s) for Region 3 of the IAPWS Industrial Formulation 1997 for the Thermodynamic Properties of Water and Steam", authorized by IAPWS at its meeting in Kyoto, Japan, September 2004. |
- Backward Equations of T(p,h), v(p,h), T(p,s) and v(p,s) for Region 3 - Boundary Equations of psat(h) and psat(s) for the Saturation Line of Region 3 |

IAPWS-IF97-04 * |
"Supplementary Release on Backward Equations p(h,s) for Region 3, Equations as a Function of h and s for the Region Boundaries, and an Equation Tsat(h,s) for Region 4 of the IAPWS Industrial Formulation 1997 for the Thermodynamic Properties of Water and Steam", authorized by IAPWS at its meeting in Kyoto, Japan, September 2004. |
- Backward Equations of p(h,s), T(h,s) and v(h,s) for Region 3 - Equations for Region Boundaries Given Enthalpy and Entropy - Backward Equations of Tsat(h,s), psat(h,s), and x(h,s) for the Two-Phase Region. |

IAPWS-IF97-Vis * |
"Release on the IAPWS Formulation 2008 for the Viscosity of Ordinary Water Substance", authorized by IAPWS at its meeting in Berlin, Germany, September 2008. |
Dynamic Viscosity Given Temperature and Density |

IAPWS-IF97-ThCond * |
"Revised Release on the IAPWS Formulation 1985 for the Thermal Conductivity of Ordinary Water Substance", authorized by IAPWS at its meeting in Berlin, Germany, September 2008. |
Thermal Conductivity Given Temperature and Density |

* : The abbreviations are given by ENGSoft.

__IAPWS-IF97
Regions__

The picture below shows the region definitions of IAPWS-IF97.

Region 1 : Sub-cooled liquid below 623.15 K temperature.

Region 2 : Superheated vapor up to 1073.15 K temperature.

Region 3 : Sub-cooled liquid or superheated vapor between Region 1 and Region 2.

Region 4 : Saturated conditions

Region 5 : Superheated vapor between 1073.15 K and 2273.15 K temperature.

Regions 1, 2, and 3 have 100 MPa pressure as upper pressure limit and Region 5 has 50 MPa as upper pressure limit. ES_StalbeIF97 has same boundary limits.

__IAPWS-IF97
Constants__

IAPWS-IF97 defines reference constants of ordinary water as below.

- Specific gas constant : R = 0.461526 kJ/kg/K

- Critical point parameters : Tc = 647.096 K, Pc = 22.064 MPa, Density_c = 322 kg/m3

- Triple point parameter : Tt = 273.16 K, Pt = 611.657 Pa, Ht = 0.611783 J/kg, St = 0, Ut = 0

Critical point is the end of saturation line.

Triple point is where the specific internal energy(Ut) and the specific entropy(St) of the saturated liquid become zero.

ES_StableIF97 has its lower pressure limit as the saturation pressure at 273.15 K (= 611.213 Pa).

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