Synonyms: Compressibility factor = Z-factor

Dimensionless multiplier describing the deviation of a fluid density from ideal gas estimate under the same pressure & temperature conditions:

Z = \frac{p V}{\nu \, R \, T} = \frac{p}{\rho} \cdot \frac{M}{R \, T}

where

c(p) = \frac{1}{p} - \frac{1}{Z} \frac{dZ}{dp}

Z(p) = \frac{Z_0}{p_0} \cdot p \cdot \exp \left[ - \int_{p_0}^p c(p) dp  \right]

c = - \frac{1}{V} \frac{dV}{dp} = - \frac{d}{dp} \left( \ln V \right) \rightarrow \ln \frac{V}{V_0} = - \int_{p_0}^p c(p) dp

Substituting from into one arrives to .

The Z-factor value is trending towards unit value () for incompressible fluids and linear pressure dependence () for strongly compressible Fluids.

There is also a good number of explicit Z-factor Correlations @models.

References