.ThermoSysPro.Properties.WaterSteam.BaseIF97

Information

Version Info and Revision history  
          

First implemented: July, 2000  
        by Hubertus Tummescheit  
        for the ThermoFluid Library with help from Jonas Eborn and Falko Jens Wagner  
          
Code reorganization, enhanced documentation, additional functions:   December, 2002  
      by Hubertus Tummescheit and moved to Modelica  
      properties library.  

Author: Hubertus Tummescheit,   
      Modelon AB  
      Ideon Science Park  
      SE-22370 Lund, Sweden  
      email: hubertus@modelon.se  
        
In September 1997, the International Association for the Properties  
        of Water and Steam (IAPWS) adopted a  
        new formulation for the thermodynamic properties of water and steam for  
        industrial use. This new industrial standard is called "IAPWS Industrial  
        Formulation for the Thermodynamic Properties of Water and Steam" (IAPWS-IF97).  
        The formulation IAPWS-IF97 replaces the previous industrial standard IFC-67.  
        Based on this new formulation, a new steam table, titled "Properties  
        of Water and Steam" by W. Wagner and A. Kruse, was published by  
        the Springer-Verlag, Berlin - New-York - Tokyo in April 1998. This  
        steam table, ref. [1] is bilingual (English /  
        German) and contains a complete description of the equations of  
        IAPWS-IF97. This reference is the authoritative source of information  
        for this implementation. A mostly identical version has been published by the International  
        Association for the Properties  
        of Water and Steam (IAPWS) with permission granted to re-publish the  
        information if credit is given to IAPWS. This document is distributed with this library as  
        IF97.pdf.  
        In addition, the equations published by IAPWS for  
        the transport properties dynamic viscosity (standards document: visc.pdf)  
        and thermal conductivity (standards document: thcond.pdf)  
        and equations for the surface tension (standards document: surf.pdf)  
        are also implemented in this library and included for reference.  
          
        The functions in BaseIF97.mo are low level functions which should  
        only be used in those exceptions when the standard user level  
        functions in Water.mo do not contain the wanted properties.  
          
Based on IAPWS-IF97, Modelica functions are available for calculating  
the most common thermophysical properties (thermodynamic and transport  
properties). The implementation requires part of the common medium  
property infrastructure of the Modelica.Thermal.Properties library in the file  
Common.mo. There are a few extensions from the version of IF97 as  
documented in IF97.pdf in order to improve performance for  
dynamic simulations. Input variables for calculating the properties are  
only implemented for a limited number of variable pairs which make sense as dynamic states: (p,h), (p,T), (p,s) and (d,T).  

1. Structure and Regions of IAPWS-IF97  
The IAPWS Industrial Formulation 1997 consists of  
a set of equations for different regions which cover the following range  
of validity:  


273,15 K < T < 1073,15 K  
p < 100 MPa  


1073,15 K < T < 2273,15 K  
p < 10 MPa  


Figure 1 shows the 5 regions into which the entire range of validity of  
IAPWS-IF97 is divided. The boundaries of the regions can be directly taken  
from Fig. 1 except for the boundary between regions 2 and 3; this boundary,  
which corresponds approximately to the isentropic line s = 5.047 kJ kg  
-1  
K-1, is defined  
by a corresponding auxiliary equation. Both regions 1 and 2 are individually  
covered by a fundamental equation for the specific Gibbs free energy g(  
p,T ), region 3 by a fundamental equation for the specific Helmholtz  
free energy f ( r,T  
), and the saturation curve, corresponding to region 4, by a saturation-pressure  
equation ps(T). The high-temperature  
region 5 is also covered by a g( p,T ) equation. These  
5 equations, shown in rectangular boxes in Fig. 1, form the so-called basic  
equations.  
        

Figure 1: Regions and equations of IAPWS-IF97  
In addition to these basic equations, so-called backward  
equations are provided for regions 1, 2, and 4 in form of  
T ( p,h ) and T (  
p,s ) for regions 1 and 2, and Ts ( p ) for region 4. These  
backward equations, marked in grey in Fig. 1, were developed in such a  
way that they are numerically very consistent with the corresponding  
basic equation. Thus, properties as functions of  p,h  
and of  p,s for regions 1 and 2, and of  
p for region 4 can be calculated without any iteration. As a  
result of this special concept for the development of the new  
industrial standard IAPWS-IF97, the most important properties can be  
calculated extremely quickly. All modelica functions are optimized  
with regard to short computing times.  
The complete description of the individual equations of the new industrial  
formulation IAPWS-IF97 is given in IF97.pdf. Comprehensive information on  
IAPWS-IF97 (requirements, concept, accuracy, consistency along region boundaries,  
and the increase of computing speed in comparison with IFC-67, etc.) can  
be taken from IF97.pdf or [2].  
[1]Wagner, W., Kruse, A. Properties of Water  
and Steam / Zustandsgrößen von Wasser und Wasserdampf / IAPWS-IF97.  
Springer-Verlag, Berlin, 1998.  
[2] Wagner, W., Cooper, J. R., Dittmann, A., Kijima,  
J., Kretzschmar, H.-J., Kruse, A., Mare� R., Oguchi, K., Sato, H., Stöcker,  
I., �fner, O., Takaishi, Y., Tanishita, I., Trübenbach, J., and Willkommen,  
Th. The IAPWS Industrial Formulation 1997 for the Thermodynamic Properties  
of Water and Steam. ASME Journal of Engineering for Gas Turbines and Power 122 (2000), 150 - 182.  


2. Calculable Properties        





Common name  

Abbreviation   

Unit  



 1  

Pressure  
p  

Pa  



 2  

Temperature  
T  

K  



 3  

Density  
d  

kg/m3  



 4  

Specific volume  
v  

m3/kg  



 5  

Specific enthalpy  
h  

J/kg  



 6  

Specific entropy  
s  

J/(kg K)  



 7  

Specific internal energy  

u  

J/kg  



 8  

Specific isobaric heat capacity  
cp  

J/(kg K)  



 9  

Specific isochoric heat capacity  
cv  

J/(kg K)  



10  

Isentropic exponent, kappa=       -(v/p)  
(dp/dv)s   
kappa (     k)  

1  



11  

Speed of sound  

a  

m/s  



12  

Dryness fraction  

x  

kg/kg  



13  

Specific Helmholtz free energy,     f = u - Ts  
f  

J/kg  



14  

Specific Gibbs free energy,     g = h - Ts  
g  

J/kg  



15  

Isenthalpic exponent,  theta     = -(v/p)(dp/dv)h  
theta (q)  

1  



16  

Isobaric volume expansion coefficient,     alpha = v-1       (dv/dT)p  

alpha  (a)  

1/K  



17  

Isochoric pressure coefficient,     beta = p-1 (dp/dT)v   
beta (b)  

1/K  



18  

Isothermal compressibility,     gamma  = -v        -1(dv/dp)T   
gamma (g)  

1/Pa  


   
19  

Dynamic viscosity  
eta (h)  

Pa s  



20  

Kinematic viscosity  
nu (n)  

m2/s  


   
21  

Thermal conductivity  
lambda (l)  

W/(m K)  



22   

Surface tension  
sigma (s)  

N/m  




The properties 1-11 are calculated by default with the functions for dynamic  
        simulation, 2 of these variables are the dynamic states and are the inputs  
        to calculate all other properties. In addition to these properties  
        of general interest, the entries to the thermodynamic Jacobian matrix which render  
        the mass- and energy balances explicit in the input variables to the property calculation are also calculated.  
        For an explanatory example using pressure and specific enthalpy as states, see the Examples sub-package.  
The high-level calls to steam properties are grouped into records comprising both the properties of general interest  
        and the entries to the thermodynamic Jacobian. If additional properties are  
        needed the low level functions in BaseIF97 provide more choice.  

Additional functions  

Function boundaryvals_p computes the temperature and the specific enthalpy and  
        entropy on both phase boundaries as a function of p  
Function boundaryderivs_p is the Modelica derivative function of boundaryvals_p  
Function extraDerivs_ph computes all entries to Bridgmans tables for all  
        one-phase regions of IF97 using inputs (p,h). All 336 directional derivatives of the  
        thermodynamic surface can be computed as a ratio of two entries in the return data, see package Common  
        for details.  
Function extraDerivs_pT computes all entries to Bridgmans tables for all  
        one-phase regions of IF97 using inputs (p,T).  


## Copyright © EDF 2002 - 2025

## ThermoSysPro Version 4.2

    

Contents

Name	Description
IterationData	constants for iterations internal to some functions
data	constant IF97 data and region limits
critical	critical point data
triple	triple point data
Regions	functions to find the current region for given pairs of input variables
Basic	Base functions as described in IAWPS/IF97
Transport	transport properties for water according to IAPWS/IF97
Isentropic	functions for calculating the isentropic enthalpy from pressure p and specific entropy s
Inverses	efficient inverses for selected pairs of variables
TwoPhase	steam properties in the two-phase rgion and on the phase boundaries