# Reduced pressure

## Description

In 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 pressure is defined as its actual pressure divided by its critical pressure.

Related formulas## Variables

p_{r} | reduced pressure (dimensionless) (dimensionless) |

p | fluid actual pressure (Pa) |

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