Software for the Reference Equation of State GERG-2008 for Natural Gases and Other Mixtures


Information about the several Windows operating systems and Excel versions are given at the end of this software description.

For the description of the reference equation of state GERG-2008 for natural gases and other mixtures see this page.

For the reference equation of state GERG-2008 for natural gases and similar mixtures, software is available that allows the calculation of more than 20 thermodynamic properties of binary mixtures, natural gases and other multi-component mixtures. These mixtures can be composed of any of the 21 components listed in the following table. The software enables to calculate thermodynamic properties in the homogeneous gas, liquid and supercritical regions, and allows to perform vapour-liquid equilibrium (VLE) calculations. The VLE calculation options comprise flash, phase envelope, dew point and bubble point calculations for any binary and multi-component mixture defined above.


Components covered by the GERG-2008 equation of state.


The software package contains a dynamic link library (DLL) and a Microsoft Excel Add-In. With the Add-In file, the property functions exported by the DLL can be added to the standard function volume of Microsoft Excel. This allows for a very simple use of the DLL from within Microsoft Excel. Furthermore, all of the exported property functions and subroutines of the DLL can be called from user-specific programs written in Fortran, C and Visual Basic. A corresponding import library file provides the information that is required for this purpose.

There are two software versions available:

• A “classical” version, where the pressure p, temperature T and total composition x (mole fractions) are the input quantities.

• An advanced version, where in addition to pressure, temperature and total composition (p,T,x ), the following combinations of input quantities can be used:

- pressure, total enthalpy and total composition (p,h,x )
- pressure, total entropy and total composition (p,s, x )
- temperature, total volume and total composition (T,v,x )
- total internal energy, total volume and total composition (u,v,x ).

The routines developed for these additional calculation options are based on special algorithms that use modern numerical procedures. They enable fast and stable property calculations. The input variables (p,h,x ) and (p,s,x ) are of particular interest for compressor and flow calculations.

For given values of the input quantities (p,T,x ) in the classical version, or (p,T,x ), (p,h,x ), (p,s,x ), (T,v,x ) and (u,v,x ) in the advanced version, the following thermodynamic properties of binary and multi-component mixtures can be calculated with the help of the DLL:






Compressibility factor






Isobaric heat capacity


Isochoric heat capacity


Speed of sound


Isentropic exponent, κ = − (v/p) (∂p/∂v)s


Joule-Thomson coefficient; μ = (∂T/∂p)h


isothermal throttling coefficient; δT = (∂h/∂p)T


Internal energy


Gibbs free energy, g = hTs


Helmholtz free energy, a = uTs


Partial derivative of pressure with respect to temperature at constant density


Partial derivative of pressure with respect to density at constant temperature


Partial derivative of density with respect to temperature at constant pressure


Partial derivative of pressure with respect to volume at constant temperature


Partial derivative of volume with respect to temperature at constant pressure


Partial derivative of entropy with respect to pressure at constant temperature


Fugacity of component i

ln φi

Logarithm of the fugacity coefficient of component i, φi =fi/(xi p)

ln Ki

Logarithm of the K-factor of component i, Ki = yi/xi


Molar vapour fraction, β = n vap/n tot


Mass vapour fraction, βm = m vap/m tot


Volume vapour fraction, βv = v vap/v tot


Molar mass


All these properties can be calulated as molar or specific values.

Examples of calculations executed with the software are shown as screenshots on this page.


The DLL and the die Excel-Files .xla, .xlam, .xls, xlsm are configurated in such away that they can be used under the several Windows operating systems [Windows 2000 to XP (32 Bit) Windows 7 and 8 (32 Bit/64 Bit)] and under the several Excel versions [2003 to 2013 (32 Bit)].

The GERG-2008 software is now available as a 64-Bit version, which can be, under the 64-Bit operating systems of Windows XP to Windows 2010 and the supplied 64-bit Excel Add-ins, incorporated into the 64-Bit versions of Excel 2010-2016. Using the supplied LIB file, the software can also be integrated into other 64-Bit applications (e.g. Matlab).

.Net DLLs are also available.

The software for GERG-2008 is not free of charge.


Contact :

Prof. em. Dr.-Ing. W. Wagner
Tel. +49 (0)234 32-29033
Fax +49 (0)234 32-14945
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