Redlich–Kwong equation of state

The Redlich–Kwong equation of state is a cubic relation among pressure, volume, and temperature that models real-fluid behavior using critical properties and a temperature-dependent attraction term.

Cubic equation of state: An equation relating pressure, temperature, and volume through a cubic expression in molar volume. Redlich–Kwong is one member of this family, alongside models with different attraction terms.
Johannes Diderik van der Waals: A Dutch physicist whose equation of state introduced corrections for molecular size and attraction. His equation supplied the cubic framework that Redlich and Kwong later modified.
Vapor–liquid equilibrium: The condition in which vapor and liquid phases coexist with equal temperature, pressure, and chemical potentials. Redlich–Kwong estimates phase fugacities used to calculate equilibrium.
Ideal gas law: The relation pressure times volume equals amount times the gas constant times temperature. It neglects molecular size and attraction, unlike Redlich–Kwong.
Critical point: The temperature and pressure at which liquid and gas phases become indistinguishable. The equation’s substance-specific constants are determined from critical properties.
Otto Redlich: An Austrian-American chemical engineer known for contributions to thermodynamics and chemical engineering. He co-developed the equation to improve real-gas predictions.
Natural gas processing: The industrial separation and treatment of natural gas to produce pipeline-ready gas and valuable products. The equation can estimate gas-phase properties in process calculations.
Redlich–Kwong equation of state limitations: The known accuracy and applicability constraints of the Redlich–Kwong real-fluid model. The original equation performs poorly for liquid volumes and some vapor-pressure predictions.
Compressibility factor: The ratio of a gas’s molar volume to its ideal-gas molar volume at the same temperature and pressure. It measures departures from ideal-gas behavior predicted by the equation.
Joseph Neng Shun Kwong: A Chinese-American chemical engineer who co-developed the Redlich–Kwong equation of state. His collaboration with Otto Redlich produced the model published in 1949.

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Real gasBroader topic: It offers a practical correction for gas properties at elevated pressures.