GERG-2008 equation of state

Important: The GERG-2008 equation of state (EOS) in AVEVA Process Simulation is currently in an experimental state.

According to Kunz and Wagner[1], the GERG-2008 EOS is an extension of the GERG-2004 EOS. The GERG-2008 EOS and GERG-2004 EOS are wide-range EOSs. Wide-range EOSs are based on multi-fluid approximations and are explicit in the Helmholtz free energy. A wide-range EOS uses other EOSs in their fundamental equation forms to calculate the thermodynamic properties and behavior for each component in the mixture. It also uses correlation equations to account for the residual mixture behavior. This model allows the GERG-2008 EOS to accurately describe the thermodynamic properties of natural gas mixtures for the entire fluid region (the homogeneous gas, liquid, and supercritical fluid phases and the vapor-liquid equilibrium states) over wide ranges of temperature, pressure, and composition. For a pure component, the GERG-2008 EOS defaults to the fundamental equation form of the EOS used for that component.

Currently, you can use the GERG-2008 EOS as a thermodynamic method override to calculate only the following thermodynamic properties:

• Liquid enthalpy

• Vapor enthalpy

• Liquid density

You can use the GERG-2008 EOS as a thermodynamic method override only when you use one of the following EOSs as the system thermodynamic method:

• Peng-Robinson (PR)

• Peng-Robinson Modified Panagiotopoulos-Reid (PRM)

• Predictive Soave-Redlich-Kwong (PSRK)

• Soave-Redlich-Kwong (SRK)

• Soave-Redlich-Kwong Huron-Vidal (SRKH)

• Soave-Redlich-Kwong Modified Panagiotopoulos-Reid (SRKM)

As a thermodynamic method override, the GERG-2008 EOS does not affect the vapor-liquid equilibrium calculations for a fluid. See Effects of specifying thermodynamic method overrides for more information.