Benedict-Webb-Rubin equation

The Benedict-Webb-Rubin equation (BWR) is an equation of state used in fluid dynamics.

The original BWR

:$P=\; ho\; RT\; +\; left(B\_0\; RT-A\_0\; -\; frac\{C\_0\}\{T^2\}\; ight)\; ho^2\; +\; left(bRT-a\; ight)\; ho^3\; +\; alpha\; a\; ho^6\; +\; frac\{c\; ho^3\}\{T^2\}left(1\; +\; gamma\; ho^2\; ight)expleft(-gamma\; ho^2\; ight)$

The BWRS Equation of State

A modification of the Benedict-Webb-Rubin equation of state by Professor Kenneth E. Starling of the University of Oklahoma.

:$P=\; ho\; RT\; +\; left(B\_0\; RT-A\_0\; -\; frac\{C\_0\}\{T^2\}\; +\; frac\{D\_0\}\{T^3\}\; -\; frac\{E\_0\}\{T^4\}\; ight)\; ho^2\; +\; left(bRT-a-frac\{d\}\{T\}\; ight)\; ho^3\; +\; alphaleft(a+frac\{d\}\{T\}\; ight)\; ho^6\; +\; frac\{c\; ho^3\}\{T^2\}left(1\; +\; gamma\; ho^2\; ight)expleft(-gamma\; ho^2\; ight)$

:"ρ" = the molar density

Values of the various parameters for 15 substances can be found in:

K.E. Starling, "Fluid Properties for Light Petroleum Systems." Gulf Publishing Company (1973).

References

*Benedict, M., Webb, G. B., and Rubin, L. C., "An Empirical Equation for Thermodynamic Properties of Light Hydrocarbons and Their Mixtures: I. Methane, Ethane, Propane, and n-Butane", J. Chem. Phys., Vol. 8, No.4, pp. 334-345 (1940).

*ibid, "II. Mixtures of Methane, Ethane, Propane and n-Butane", J. Chem. Phys., Vol. 10, No. 12, pp. 747 - 758 (1942).
*ibid, "III. Constants for Twelve Hydrocarbons", Chem. Eng. Progr., Vol. 47, No. 8, pp. 419-422 (1951).
*ibid, "IV. Fugacities and Liquid-Vapor Equilibria", Chem. Engr. Progr., Vol. 47, No. 9, pp. 449-454 (1951).
* R.C. Reid, J.M. Prausnitz, B.E. Poling: "The Properties of Gases & Liquids", 4th Ed., McGraw-Hill, New Vork 1987