New Reference Equation of State for Carbon Dioxide

Published

May 6, 2022

Author(s)

Allan Harvey, Eric Lemmon

Abstract

For carbon dioxide, the current reference for thermodynamic properties is the equation of state (EOS) of Span and Wagner published in 1996. While the Span-Wagner EOS provides accurate properties at most conditions of industrial interest, some deficiencies have been identified since it was developed. NIST has developed a replacement for the Span-Wagner EOS. The new EOS makes use of state-of-the-art molecular calculations for the ideal-gas heat capacity and for the thermal virial coefficients, improving accuracy for the gas phase and allowing extrapolation to temperatures above the range of experimental data. The functional form of the EOS has been optimized to prevent spurious near-critical behavior and to avoid problems with mixture calculations. The new EOS represents the available experimental data as well as or better than the Span-Wagner EOS. The behavior is greatly improved outside the region where extensive measurements exist, and calculational speed has been improved by roughly a factor of 1.5–2. The new EOS will be made available for use in NIST's REFPROP software.

Proceedings Title

7th International Supercritical CO2 Power Cycles Symposium

Conference Dates

February 21-24, 2022

Conference Location

San Antonio, TX, US

Pub Type

Conferences

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Keywords

carbon dioxide, equation of state, thermodynamic properties

Citation

Harvey, A. and Lemmon, E. (2022), New Reference Equation of State for Carbon Dioxide, 7th International Supercritical CO2 Power Cycles Symposium, San Antonio, TX, US, [online], https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=929350 (Accessed October 8, 2025)