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NIST Standard Reference Database 23

NIST Reference Fluid Thermodynamic and Transport Properties Database (REFPROP): Version 9.1

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Customers who purchased version 9.0 can receive version 9.1 for free. Please email to with SRD order number for version 9.0.


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Effective immediately, there will be a minimum $30.00 shipping charge for all international shipments of databases via UPS International. Customer will be responsible for their own duties, tax, and VAT. Contact 301 975 2200 or if you have questions.

REFPROP 9.1 has replaced the NIST 12 and 14 databases

New Features of REFPROP Version 9.1 

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. The number of enhancements has been substantial, with some of the more important ones listed below:

  • Convergence along the saturation lines is now much better and faster 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.
  • A 64-bit version of the DLL is available for use with Excel or Matlab.
  • The addition of the following fluids:  cyclopentane, diethyl ether, ethylbenzene, hydrogen chloride, isooctane, m-xylene, Novec649, o-xylene, p-xylene, RE143a, R40, R1216, RE245cb2, RE245fa2, RE347mcc, R1233zd.
  • The equations of state have been revised for benzene, cyclohexane, deuterium, dimethyl carbonate, ethanol, helium, R161, and R1234ze.
  • Transport equations have been added or modified for many of the fluids, including:  hydrogen, Novec649, parahydrogen, deuterium, isooctane, benzene, toluene,  SO2, hexane, heptane, RE347mcc, R236fa, R236ea, R245fa, SF6, ethanol, water, and all of the siloxanes.
  • MatLab routines now use the Refprop DLL directly and can be directly modified.
  • Additional plots for analyzing equations of state are available.

Version 9.0 expands the capability of the REFPROP database. New features include: 

  • Additional pure fluids and updated equations of state and transport equations, including cyclopentane, R-1234yf, and R-1234ze(E). 
  • The number of binary mixtures with interaction parameters has increased from 303 to 639, including many mixtures of ethylene, propylene, methanol, ethanol, toluene, benzene, cyclohexane, sulfur dioxide, ammonia, dodecane, acetone, and butylene.
  • Expanded support for natural gas systems, including the addition of the GERG-2008 mixture model for natural gas fluids, which includes binary interaction parameters for the following fluids: argon, butane, carbon monoxide, carbon dioxide, decane, ethane, helium, heptane, hexane, hydrogen, hydrogen sulfide, isobutane, isopentane, methane, nitrogen, nonane, octane, oxygen, pentane, propane, and water.
  • Convergence along the saturation lines is now better for complex mixtures due to new algorithms for finding phase boundaries and the addition of analytical derivatives in the calculation of the fugacity. 
  • Calculation of net and gross heating values for natural gas systems.
  • Additional pure fluid equations can be loaded in memory that are not included in a selected mixture. 
  • New plots that show deviations between the GERG-2008 equation and the AGA-8 natural gas mixture models. 

Version 9.1 includes 121 pure fluids, 5 pseudo-pure fluids (such as air), and mixtures with up to 20 components:

  • The typical natural gas constituents methane, ethane, propane, butane, isobutane, pentane, isopentane, hexane, isohexane, heptane, octane, nonane, decane, undecane, dodecane, carbon dioxide, carbon monoxide, hydrogen, nitrogen, and water.
  • The hydrocarbons acetone, benzene, butene, cis-butene, cyclohexane, cyclopentane, cyclopropane, ethylene, isobutene, isooctane, methylcyclohexane, propylcyclohexane, neopentane, propyne, trans-butene, and toluene.
  • The HFCs R23, R32, R41, R125, R134a, R143a, R152a, R161, R227ea, R236ea, R236fa, R245ca, R245fa, R365mfc, R1233zd(E), R1234yf, and R1234ze(E).
  • The refrigerant ethers RE143a, RE245cb2, RE245fa2, and RE347mcc (HFE-7000).
  • The HCFCs R21, R22, R123, R124, R141b, and R142b.
  • The traditional CFCs R11, R12, R13, R113, R114, and R115.
  • The fluorocarbons R14, R116, R218, R1216, C4F10, C5F12, and RC318.
  • The "natural" refrigerants ammonia, carbon dioxide, propane, isobutane, and propylene.
  • The main air constituents nitrogen, oxygen, and argon.
  • The noble elements helium, argon, neon, krypton, and xenon.
  • The cryogens argon, carbon monoxide, deuterium, krypton, neon, nitrogen trifluoride, nitrogen, fluorine, helium, methane, oxygen, normal hydrogen, parahydrogen, and orthohydrogen.
  • Water (as a pure fluid, or mixed with ammonia).
  • Miscellaneous substances including carbonyl sulfide, diethyl ether, dimethyl carbonate, dimethyl ether, ethanol, heavy water, hydrogen chloride, hydrogen sulfide, methanol, methyl chloride, nitrous oxide, Novec-649, sulfur hexafluoride, sulfur dioxide, and trifluoroiodomethane.
  • The xylenes m-xylene, o-xylene, p-xylene, and ethylbenzene.
  • The FAMES (fatty acid methyl esters, i.e., biodiesel constituents) methyl oleate, methyl palmitate, methyl stearate, methyl linoleate, and methyl linolenate.
  • The siloxanes octamethylcyclotetrasiloxane, decamethylcyclopentasiloxane, dodecamethylcyclohexasiloxane, decamethyltetrasiloxane, dodecamethylpentasiloxane, tetradecamethylhexasiloxane, octamethyltrisiloxane, and hexamethyldisiloxane.
  • 79 predefined mixtures (such as R407C, R410A, and air); the user may define and store others.

The program uses the most accurate equations of state and models currently available: 

  • High accuracy Helmholtz energy equations of state, including international standard equations for water, R134a, R32, and R143a and equations from the literature for ethane, propane, R125, ammonia, carbon dioxide, and others. 
  • High accuracy MBWR equations of state, including the international standard EOS for R123. 
  • The Bender equation of state for several of the "older" refrigerants, including R14, R114, and RC318. 
  • An extended corresponding states model for fluids with limited data. 
  • An excess Helmholtz energy model for mixture properties.
  • Experimentally based values of the mixture parameters are available for hundreds of mixtures.
  • The American Gas Association equation AGA8 for natural gas properties (as an alternative to the Helmholtz model).
  • Viscosity and thermal conductivity are based on fluid-specific correlations (where available), a modification of the extended corresponding states model, or the friction theory model.

Available properties: 

  • Temperature, Pressure, Density, Energy, Enthalpy, Entropy, Cv, Cp, Sound Speed, Compressibility Factor, Joule Thomson Coefficient, Quality, 2nd and 3rd Virial Coefficients, 2nd and 3rd Acoustic Virial Coefficients, Helmholtz Energy, Gibbs Energy, Heat of Vaporization, Fugacity, Fugacity Coefficient, Chemical Potential, K value, Molar Mass, B12, Thermal Conductivity, Viscosity, Kinematic Viscosity, Thermal Diffusivity, Prandtl Number, Surface Tension, Dielectric Constant, Gross and Net Heating Values, Isothermal Compressibility, Volume Expansivity, Isentropic Coefficient, Adiabatic Compressibility, Specific Heat Input, Exergy, Gruneisen, Critical Flow Factor, Excess Values, dp/dr, d2p/dr2,  dp/dT, dr/dT, dp/dr, d2p/dr2 

Windows®-based, graphical user interface features: 

  • The fluid or mixture, units, reference state, properties to be displayed, and other options are specified via pull down menus. 
  • A wide variety of tables - in a scrollable, spreadsheet style format - may be calculated, including saturation properties (with temperature, pressure, density, enthalpy, entropy, composition, or quality as the independent variable) and tables at constant temperature, pressure, density, volume, enthalpy, or entropy (with temperature, pressure, or density varied). 
  • Input properties may be read from a file. 
  • Data in any table can be copied to the clipboard for export to other programs (such as spreadsheets). 
  • Data in any table can be plotted. 
  • A wide variety of property diagrams may be automatically generated, including pressure-enthalpy and temperature-entropy diagrams and (for binary mixtures) temperature-composition and pressure-composition plots. 
  • User preferences and entire sessions may be stored for later use. 
  • A fluid search dialog is available to find fluids that match a certain criteria. 
  • A complete help system is available.

Source code: The FORTRAN subroutines and associated fluid data files are provided for those wishing to access REFPROP calculations from their own applications.

Excel spreadsheets:  A sample spreadsheet is included that demonstrates how the REFPROP DLL can be linked to Excel. Most properties that are available in the graphical interface can also be calculated in the spreadsheet.

System Requirements: PC running Windows® 98, 2000, XP, Vista, Window 7 or similar operating system; 10.0 MB available hard disk space.

Click here to view the PDF version of Users' Guide.

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For additional information contact:

Standard Reference Data Program
National Institute of Standards and Technology
100 Bureau Dr., Stop 8550
Gaithersburg, MD 20899-8550
(301) 975-2200 (VOICE)
(301) 975-4553 (FAX)
Contact Us (E-MAIL)

Scientific contacts for the database:

Thermodynamic properties, graphical interface, and Excel spreadsheets:

Eric W. Lemmon
Physical and Chemical Properties Division
National Institute of Standards and Technology
Boulder, CO 80305-3328
(303) 497-7939

Transport properties:

Marcia L. Huber
Physical and Chemical Properties Division
National Institute of Standards and Technology
Boulder, CO 80305-3328
(303) 497-5252

Keywords: air; alternative refrigerants; CFC; chemical engineering; chemistry; chlorofluorocarbons; cryogens; hydrochlorofluorocarbons; equation of state; fluids; hydrocarbons; HCFC; HFC; mixtures; natural gas; refrigerants; thermodynamic property; thermodynamics; thermophysics; transport property