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Properties of Gases and Liquids (RPP)

Contents

Source

Methods for calculating pure component properties from:

The Properties of Gases & Liquids, 4th Edition Reid, Prausnitz and Polling, 1987, McGraw-Hill

All methods use SI units.

Ideal Gas Molar Heat Capacity (Constant Pressure)

Properties of Gases and Liquids uses the following correlation for the ideal gas molar heat capacity:

c_{\text{p ig}} = A + B \times T + C \times T^2 + D \times T^3

Parameters

Symbol Parameter Name Units Description
A cp_mol_ig_comp_coeff_A \text{J/mol}\cdotp\text{K}  
B cp_mol_ig_comp_coeff_B \text{J/mol}\cdotp\text{K}^2  
C cp_mol_ig_comp_coeff_C \text{J/mol}\cdotp\text{K}^3  
D cp_mol_ig_comp_coeff_D \text{J/mol}\cdotp\text{K}^4  

Ideal Gas Molar Enthalpy

The correlation for the ideal gas molar enthalpy is derived from the correlation for the molar heat capacity and is given below:

h_{\text{ig}} - h_{\text{ig ref}} = A \times (T-T_{ref}) + \frac{B}{2} \times (T^2 - T_{ref}^2) + \frac{C}{3} \times (T^3 - T_{ref}^3) + \frac{D}{4} \times (T^4 - T_{ref}^4) + \Delta h_{\text{form, Vap}}

Parameters

Symbol Parameter Name Units Description
A cp_mol_ig_comp_coeff_A \text{J/mol}\cdotp\text{K}  
B cp_mol_ig_comp_coeff_B \text{J/mol}\cdotp\text{K}^2  
C cp_mol_ig_comp_coeff_C \text{J/mol}\cdotp\text{K}^3  
D cp_mol_ig_comp_coeff_D \text{J/mol}\cdotp\text{K}^4  
\Delta h_{\text{form, Vap}} enth_mol_form_vap_comp_ref Base units Molar heat of formation at reference state

Note

This correlation uses the same parameters as the ideal gas heat capacity correlation. Units of molar heat of formation will be derived from the base units defined for the property package.

Ideal Gas Molar Entropy

The correlation for the ideal gas molar entropy is derived from the correlation for the molar heat capacity and is given below:

s_{\text{ig}} = A \times ln(T/T_{ref}) + B \times (T - T_{ref}) + \frac{C}{2} \times (T^2 - T_{ref}^2) + \frac{D}{3} \times (T^3 - T_{ref}^3) + s_{\text{form, Vap}}

Parameters

Symbol Parameter Name Units Description
A cp_mol_ig_comp_coeff_A \text{J/mol}\cdotp\text{K}  
B cp_mol_ig_comp_coeff_B \text{J/mol}\cdotp\text{K}^2  
C cp_mol_ig_comp_coeff_C \text{J/mol}\cdotp\text{K}^3  
D cp_mol_ig_comp_coeff_D \text{J/mol}\cdotp\text{K}^4  
s_{\text{form, Vap}} entr_mol_form_vap_comp_ref Base units Standard molar entropy of formation at reference state

Note

This correlation uses the same parameters as the ideal gas heat capacity correlation . Units of molar entropy of formation will be derived from the base units defined for the property package.

Saturation (Vapor) Pressure

Properties of Gases and Liquids uses the following correlation to calculate the vapor pressure of a component:

ln(\frac{P_{sat}}{P_{crit}}) \times (1-x) = A \times x + B \times x^1.5 + C \times x^3 + D \times x^6

where x = 1 - \frac{T}{T_{crit}}.

Symbol Parameter Name Units Description
A pressure_sat_comp_coeff_A None  
B pressure_sat_comp_coeff_B None  
C pressure_sat_comp_coeff_C None  
D pressure_sat_comp_coeff_D None  
P_{crit} pressure_crit_comp Same as system pressure Critical pressure
T_{crit} temperature_crit_comp Same as system temperature Critical temperature

Note

This correlation is only valid at temperatures below the critical temperature. Above this point, there is no real solution to the equation.