PRM — Peng-Robinson Modified Panagiotopolous-Reid method

The Peng-Robinson Modified Panagiotopoulos-Reid (PRM) method is a modified version of the Peng-Robinson equation of state. See PR — Peng-Robinson equation of state for more information.

First, we use the Panagiotopoulos-Reid modification by using an asymmetric mixing rule that contains two adjustable interaction parameters, kij and kji. This significantly improves the accuracy of predictions for mixtures of polar and nonpolar components. Second, we use a SimSci modification of the mixing rule and introduce two more adjustable parameters, cij and cji. This improves the prediction for polar-nonpolar systems where the non-ideality is large or strongly asymmetric.

The thermodynamic data banks in AVEVA Thermodynamic Data Manager supply these parameters for many binary systems of chemicals to this modified mixing rule.

We also use an improved α correlation developed by SimSci, which provides more accurate vapor pressure predictions than the original PR formulation for a wide variety of components.

In addition to fugacity coefficients, you can use the PRM method to predict the enthalpies, entropies, and densities for the liquid and vapor phases.