Simple editing mode
In simple editing mode, pre-defined model sets are available. All that is required for a standard-configuration of a Property Package is selection of compounds and a model set. This will select the VLE equilibrium server, a standard set of properties, and corresponding property calculation methods. Any more advanced modifications to the package set up can be done using the items in the Configure menu. Changing advanced options will cause the model set to change to Custom. Re-selecting a model set once in Custom configuration mode, will overwrite any existing property and model selections.
Before selecting a model set, it is best to first add the desired compounds. This will prevent any warnings or errors from being shown that would not be shown in case the compounds had already been selected. Vice versa, when presence of particular compounds cause issues with the selected model set, these warnings will only be at model selection if the compounds have already been added.
The pre-defined model sets can be divided into two groups: EOS (Equation of State) based models, and Activity based models.
All models will use default calculation routines for the following properties: ideal gas enthalpy, surface tension, viscosity, thermal conductivity, heat capacity, Gibbs free energy and molecular weight. For all model sets, the COSTALD liquid density model is selected by default.
EOS based model sets
For EOS based model sets, vapor and liquid phase will use the same equation of state. The following properties are based on the equation of state: compressibility factor, fugacity, enthalpy, entropy and vapor density. The following model sets are available:
- Peng Robinson: uses the Peng Robinson Equation of State for the vapor and liquid phase.
- Soave Redlich Kwong: uses the Soave Redlich Kwong Equation of State for the vapor and liquid phase.
Activity based model sets
All activity based model sets will use the ideal gas model for the vapor phase fugacity, density, enthalpy and entropy. A compound-based default model will be selected for heat of vaporization. Fugacity for the liquid phase will be defined by the DECHEMA model (which does not include the saturated vapor fugacity or Poynting correction). The liquid excess entropy and enthalpy are based on the activity coefficient. The following models are available for the liquid activity:
- Wilson: uses the Wilson model for liquid phase activity
- NRTL: uses the NRTL model for liquid phase activity
- UNIFAC VLE: uses the UNIFAC VLE model for liquid phase activity
- UNIQUAC: uses the UNIQUAC model for liquid phase activity
- Chemical Theory (Prausnitz): uses the UNIQUAC-Q' model for liquid phase activity; the liquid fugacities and enthalpies follow the Prausnitz formulation based on a liquid reference fugacity. The vapor phase uses the Hayden O'Connel equation of state with the Chemical Theory model. This model describes non-idealities resulting dimerization in the vapor phase, such as for carboxylic acids.