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An Equation of State for the Thermodynamic Properties of Helium



Diego Ortiz Vega, Kenneth Hall, James Holste, Allan H. Harvey, Eric W. Lemmon


This report documents the equation of state for fluid helium implemented in Version 10 of NIST's REFPROP Standard Reference Database. The equation of state is expressed as the molar Helmholtz energy as a function of temperature and density, and is valid for the normal fluid (helium I) up to 1500 K and 2000 MPa. Limited comparisons with experimental data and with virial coefficients calculated by ab initio methods are provided.
NIST Interagency/Internal Report (NISTIR) - 8474
Report Number


equation of state, helium, thermodynamic properties, virial coefficients


Ortiz Vega, D. , Hall, K. , Holste, J. , Harvey, A. and Lemmon, E. (2023), An Equation of State for the Thermodynamic Properties of Helium, NIST Interagency/Internal Report (NISTIR), National Institute of Standards and Technology, Gaithersburg, MD, [online],, (Accessed April 16, 2024)
Created August 10, 2023, Updated November 6, 2023