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NIST Standard Reference Database 23: Reference Fluid Thermodynamic and Transport Properties-REFPROP, Version 9.1



Eric W. Lemmon, Marcia L. Huber, Mark O. McLinden


This is a new release of the NIST Standard Reference Database 23, commonly known as REFPROP. Enhancements have been made to most areas of the NIST REFPROP program, including the graphical interface, the Excel spreadsheet, the FORTRAN files (i.e., core property routines), the sample programs in C++, MatLab, VB, etc., and additional fluids. Convergence along the saturation lines is now better for complex mixtures due to new algorithms for finding phase boundaries, the addition of analytical derivatives in the calculation of the fugacity, and spline curves to provide initial inputs to the phase boundary routines. The FORTRAN code was organized to be threadsafe and allow multi-core processing, and a 64-bit version of the DLL is available for use with Excel or Matlab. Several new fluids have been added inlcuding: diethyl ether, ethylbenzene, hydrogen chloride, m-xylene, o-xylene, p-xylene, RE-143m, R-40, RE-1216, RE-245cb2, RE-245fa2, and RE-347mcc. Equations of state have been revised for ammonia, dimethyl carbonate, ethanol, and helium, and a new mixture model for ammonia/water was developed. Thermal conductivity and/or viscosity equations have been added or modified for the following fluids: hydrogen, parahydrogen, toluene, RE-347mcc, SF6, benzene, and several siloxanes. In addition, the international standard formulation adopted by IAPWS for the thermal conductivity of water has been added.
Natl Std. Ref. Data Series (NIST NSRDS) -


Reference Fluid, REFPROP, equations of state, refrigerants


Lemmon, E. , Huber, M. and McLinden, M. (2013), NIST Standard Reference Database 23: Reference Fluid Thermodynamic and Transport Properties-REFPROP, Version 9.1, Natl Std. Ref. Data Series (NIST NSRDS), National Institute of Standards and Technology, Gaithersburg, MD, [online], (Accessed May 26, 2024)


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Created May 7, 2013, Updated June 2, 2021