# Reduced specific volume

## Description

In thermodynamicsIn thermodynamics, the reduced properties of a fluid are a set of state variables normalized by the fluid’s state properties at its critical point. These dimensionless thermodynamic coordinates, taken together with a substance’s compressibility factor, provide the basis for the simplest form of the theorem of corresponding states.

Reduced properties are also used to define the Peng–Robinson equation of state, a model designed to provide reasonable accuracy near the critical point. They are also used to critical exponents, which describe the behavior of physical quantities near continuous phase transitions.

The reduced specific volume (or pseudo-reduced specific volume) of a fluid is computed from the ideal gas law at the substance’s critical pressure and temperature. This property is useful when the specific volume and either temperature or pressure are known, in which case the missing third property can be computed directly.

Related formulas## Variables

v_{r} | reduced specific volume (mol) |

v | actual measured volume (m^{3}) |

p_{c} | fluid critical pressure (Pa) |

R | molar gas constant |

T_{c} | fluid critical temperature (K) |