Limitations of the PRM method

Due to the asymmetric nature of the Panagiotopoulos-Reid mixing rule, you may get slightly different results for a system that has more than one instance of the same pure component compared to an identical system that has only one instance of that pure component. For example, if you add two ethanol components, ethanol-1 and ethanol-2, to a compositional Fluid Type and you split the total ethanol compositional fraction between them, AVEVA Thermodynamic Data Manager may not calculate the same property values as a similar compositional Fluid Type that includes only a single ethanol component. The variations between two such Fluid Types is very small, but we recommend that you use the PRM method only for compositional Fluid Types that have a single instance of each pure component.

If your Fluid Type contains a large number of petro components (>150), you should use this method with caution. This situation is similar to splitting a single component into a large number of similar components and has the same limitations as Fluid Types that include more than one instance of a pure component. We recommend that you do not use the Peng-Robinson Modified Panagiotopoulos-Reid (PRM) method for compositional Fluid Types that contain a large number of petro components.

The predicted liquid-phase densities are not very accurate. We recommend that you do not use the PRM method to predict liquid-phase densities.