| For
the description of the reference equation of state GERG-2008
for natural gases and other mixtures, see
this page,
where also the difference between the equations of state GERG-2004
and GERG-2008 is explained.
For the reference
equation of state GERG-2008 for natural gases and other 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 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:
| ρ |
Density |
| v |
Volume |
| Z |
Compressibility factor |
| h |
Enthalpy |
| s |
Entropy |
| cp |
Isobaric heat capacity |
| cv |
Isochoric heat capacity |
| w |
Speed of sound |
| κ |
Isentropic exponent, κ = −
(v/p) (∂p/∂v)s |
| μ |
Joule-Thomson coefficient; μ
= (∂T/∂p)h |
| δT |
isothermal throttling coefficient; δT
= (∂h/∂p)T |
| u |
Internal energy |
| g |
Gibbs free energy, g
= h − Ts |
| a |
Helmholtz free energy, a
= u − Ts |
| (∂p/∂T)ρ |
Partial derivative of pressure with
respect to temperature at constant density |
| (∂p/∂ρ)T |
Partial derivative of pressure with respect
to density at constant temperature |
| (∂ρ/∂T)p |
Partial derivative of density with respect
to temperature at constant pressure |
| (∂p/∂v)T |
Partial derivative of pressure with respect
to volume at constant temperature |
| (∂v/∂T)p |
Partial derivative of volume with respect
to temperature at constant pressure |
| (∂s/∂p)T |
Partial derivative of entropy with respect to pressure
at constant temperature |
| fi |
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 |
| β |
Molar vapour fraction, β = nvap/ntot |
| βm |
Mass vapour fraction, βm =
mvap/mtot |
| βv |
Volume vapour fraction, βv =
vvap/vtot |
| M |
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 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
wagner@thermo.rub.de
|
