# Peng-Robinson Equation of State

on . Posted in Thermodynamics

Peng-Robinson equation of state is a widely used thermodynamic model for describing the behavior of fluids, especially gases and liquids.  The Peng-Robinson equation is an improvement over the Van der Waals equation and aims to provide a more accurate representation of real fluid behavior, particularly for non-ideal gases and liquids.

The parameter "a" accounts for the molecular attractions between particles, while the parameter "b" accounts for the volume occupied by the molecules themselves.  These parameters are determined based on the critical properties (critical temperature and critical pressure) and acentric factor of the fluid.

The Peng-Robinson equation of state can be used to calculate various thermodynamic properties of the fluid, including pressure, volume, temperature, and compressibility factor.  It is particularly useful in the design and analysis of chemical processes, petroleum engineering, and other fields where accurate modeling of fluid behavior is important.

### Peng-Robinson Equation of State

$$p = (R \; T \;/\; V - b ) - [\; a \;/\; V \; (V + b ) + b \; (V - b )\; ]$$
Symbol English Metric
$$p$$ = pressure of fluid $$lbf \;/\; in^2$$ $$Pa$$
$$R$$ = universal gas constant $$lbf-ft\;/\;lbmol-R$$ $$J\;/\;kmol-K$$
$$T$$ = temperature $$F$$ $$K$$
$$V$$ = molar volume of fluid $$in^3$$ $$mm^3$$
$$b$$ = parameters specific to the fluid, known as the Peng-Robinson parameters $$in^3$$  $$mm^3$$
$$a$$ = parameters specific to the fluid, known as the Peng-Robinson parameters - -

Tags: Gas Ideal Gas