Ideal Gases and Liquids (Ideal)

Introduction

Ideal behavior represents the simplest possible equation of state that ensures thermodynamic consistency between different properties.

Critical Properties of Mixtures

The Ideal Equation of State module does not support the calculation of mixture critical properties as the ideal equation of state cannot represent the critical point.

Mass Density by Phase

The following equation is used for both liquid and vapor phases, where \(p\) indicates a given phase:

\[\rho_{mass, p} = \rho_{mol, p} \times MW_p\]

where \(MW_p\) is the mixture molecular weight of phase \(p\).

Molar Density by Phase

For the vapor phase, the Ideal Gas Equation is used to calculate the molar density;

\[\rho_{mol, Vap} = \frac{P}{RT}\]

whilst for the liquid phase the molar density is the weighted sum of the pure component liquid densities:

\[\rho_{mol, Liq} = \sum_j{x_{Liq, j} \times \rho_{Liq, j}}\]

where \(x_{Liq, j}\) is the mole fraction of component \(j\) in the liquid phase.

Molar Enthalpy by Phase

For both liquid and vapor phases, the molar enthalpy is calculated as the weighted sum of the component molar enthalpies for the given phase:

\[h_{mol, p} = \sum_j{x_{p, j} \times h_{mol, p, j}}\]

where \(x_{p, j}\) is the mole fraction of component \(j\) in the phase \(p\).

Component Molar Enthalpy by Phase

Component molar enthalpies by phase are calculated using the pure component method provided by the users in the property package configuration arguments.

Molar Entropy by Phase

For both liquid and vapor phases, the molar entropy is calculated as the weighted sum of the component molar entropies for the given phase:

\[s_{mol, p} = \sum_j{x_{p, j} \times s_{mol, p, j}}\]

where \(x_{p, j}\) is the mole fraction of component \(j\) in the phase \(p\).

Component Molar Entropy by Phase

Component molar entropies by phase are calculated using the pure component method provided by the users in the property package configuration arguments.

Component Fugacity by Phase

For the vapor phase, ideal behavior is assumed:

\[f_{Vap, j} = P\]

For the liquid phase, Raoult’s Law is used:

\[f_{Liq, j} = P_{sat, j}\]

Component Fugacity Coefficient by Phase

Ideal behavior is assumed, so all \(\phi_{p, j} = 1\) for all components and phases.

Molar Gibbs Energy by Phase

For both liquid and vapor phases, the molar Gibbs energy is calculated as the weighted sum of the component molar Gibbs energies for the given phase:

\[g_{mol, p} = \sum_j{x_{p, j} \times g_{mol, p, j}}\]

where \(x_{p, j}\) is the mole fraction of component \(j\) in the phase \(p\).

Component Gibbs Energy by Phase

Component molar Gibbs energies are calculated using the definition of Gibbs energy:

\[g_{mol, p, j} = h_{mol, p, j} - s_{mol, p, j} \times T\]