Acentric Factor formula |
||
|
\( \omega \;=\; -log_{10} (P_r^{sat}) \: | _{T_r = 0.7} -1 \) \( T_r \;=\; \frac{ T }{ T_c } \) |
||
| Symbol | English | Metric |
| \( \omega \) (Greek Symbol omega) = Acentric Factor | - | \(dimensionless\) |
| \( P_r^{sat}) \) = Reduced Saturation Vapor Pressure | - | \(Pa\) |
| \( T_r \) = Reduced Temperature | - | \(^\circ K\) |
| \( T \) = System Temperature | - | \(^\circ K\) |
| \( T_c \) = Critical Temperature | - | \(^\circ K\) |
Acentric factor is a dimensionless thermodynamic property that quantifies how much a real fluid’s molecular shape and intermolecular forces cause it to deviate from the behavior of an ideal, spherical (simple) molecule. It is defined based on the substance’s reduced saturation vapor pressure at a reduced temperature of 0.7, and it effectively measures molecular non-sphericity and polarity.
Substances with nearly spherical, nonpolar molecules, such as noble gases, have acentric factors close to zero, while larger, more complex, or polar molecules have higher values. The acentric factor is widely used in corresponding-states correlations and cubic equations of state (such as the Soave-Redlich–Kwong and Peng–Robinson equations) to improve predictions of vapor–liquid equilibrium, compressibility, and other thermophysical properties of real fluids.
