View Source

One of the cubic equations of real gas state defining the Compressibility factor as a function of fluid pressure and fluid temperature :

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

A= 0.45724 \cdot \alpha \cdot \frac{p_r}{T_r^2}

B=0.07780 \cdot \frac{p_r}{T_r}

\alpha = \left( 1 + \kappa \, (1-T_r^{0.5}) \right)^2

\kappa = \kappa_0 + 
\left[ 
\kappa_1 + \kappa_2 (\kappa_3 - T_r) (1-T_r^{0.5})
\right]\, (1+T_r^{0.5}) \, (0.7 - T_r)

\kappa_0 = 0.378893 + 1.4897153 \, \omega -0.17131848 \, \omega^2 +0.0196554 \, \omega^3

where

Once compressibility Z-factor is known the fluid density can be calculated as:

\rho(p, T) = \frac{1}{Z(p,T)} \cdot \frac{M}{R} \cdot \frac{p}{T}

where