Peng-Robinson gas

The Peng-Robinson 57 equation of state for gases.

Density, $\rho$ [kg/m$^3$]

$$\rho = \frac{p}{Z R T}$$

Here, $Z$ is computed from the cubic equation:

$$Z^3 - (1 - B)Z^2 + (A - 2B - 3B^2)Z - (AB - B^2 - B^3) = 0$$

Where:

$$A = \frac{\alpha a p}{R^2 T^2}; B = \frac{bp}{RT}.$$

with:

• $a = 0.45724 \frac{R^2 T_c^2}{p_c}$
• $b = 0.07780 \frac{R T_c}{p_c}$
• $\alpha = \left(1 + \kappa (1 - T_r^{0.5}) \right)^2$
• $\kappa = 0.37464 + 1.564226 \omega - 0.26992 \omega^2$
• $T_r = \frac{T}{T_c}$

Entropy, $S$ [J/kg/K ]

$$S = ...$$

Compressibility, $\psi$ [s$^2$/m$^2$]

$$\psi = \frac{1}{Z R T}$$

Usage

The PengRobinsonGas equation of state is specified as:

equationOfState
{
    Tc          <scalar>;
    Vc          <scalar>;
    Pc          <scalar>;
    omega       <scalar>;
}

Where

• Tc : Critical temperature [K]
• Vc : Critical volume [m$^3$/kmol]
• Pc : Critical pressure [Pa]
• omega : Accentric factor [-]

Further information

Source code

• PengRobinsonGas