# Peng–Robinson equation of state

## Description

The Peng–Robinson equation of state (PR EOS) was developed in 1976 at The University of Alberta by Ding-Yu Peng and Donald Robinson in order to satisfy the following goals:

The parameters should be expressible in terms of the critical properties and the acentric factor. The model should provide reasonable accuracy near the critical point, particularly for calculations of the compressibility factor and liquid density. The mixing rules should not employ more than a single binary interaction parameter, which should be independent of temperature pressure and composition. The equation should be applicable to all calculations of all fluid properties in natural gas processes.For the most part the Peng–Robinson equation exhibits performance similar to the Soave equation, although it is generally superior in predicting the liquid densities of many materials, especially nonpolar ones. The departure functions of the Peng–Robinson equation are given on a separate article.

Related formulas## Variables

p | absolute pressure (Pa) (Pa) |

R | molar gas constant |

T | absolute temperature (K) (K) |

V_{m} | molar volume (m3/mol) (m^{3}/mol) |

b | b component (m^{3}/mol) |

a | a component (J*m^{3}/mol^{2}) |

α | α component (dimensionless) (dimensionless) |