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Answers to Frequently Asked Questions

The following information gives answers to some of the most frequently asked questions concerning the REFPROP program (https://www.nist.gov/srd/refprop). To download any of the files listed below, right-click on the file and select Save Target As... and then add the file to your REFPROP or other appropriate directory. Sections with new information added during the last several months are identified with a «. For questions not answered here, please see the user's guide

Please see the additional pages on the right-hand-side for additional information:

  • [Using The Graphical User Interface](Using The Graphical User Interface)
  • [Error Messages](Error Messages)
  • Programming
  • Fluids

Getting Help

Before contacting us, please look in the Help file – most answers can be found there. If you need to contact us regarding questions that are not answered below, do not send separate emails to those of us that support this work. Rather, include each person in the same email so that it is not necessary for each of us to respond to your question. This will free up resources to develop better products.

Furthermore, when you do report problems with the use of REFPROP, here is information that is crucial for us to know to be able to help you:

  • What version of REFPROP do you use?
  • What operating system do you use (windows, OSX, linux, etc.)?
  • What exactly did you do to cause the problem you see?
  • What error message do you get? (The comment "it doesn't work" doesn't help us help you). Screenshots of the failure are very helpful.

Changelog

There are a few changes in versions 9.0 and 9.1 that may confuse you when you first run the program. The number of fluids will appear to be much shorter. Look under Substance/Specify Fluid Set and you will see the ability to select a set of fluids rather than list all of them. In the Options/Properties menu, the composition box is now missing from the Thermodynamic tab; you will find it in the Mixtures tab along with other properties that are generally displayed only for mixtures. When copying data from a table, the headers are no longer copied with the data. If you like that feature, select it in Options/Preferences, then save the defaults.prf file under Options/Save Current Options. Concerning the Fortran files and the calling routines to the DLL, all of the inputs/outputs to the routines are the same as those to 8.0 so your own code will not have to be updated. Just replace your old DLL with that from 9.0 or 9.1 and you will be set to go (of course you will also need the new FLD files and the HMX.BNC file).

Issues with Refprop 9.0

  1. The calculation of d2p/dT2 at constant density is incorrect.
  2. The reference state for R1234yf and ze should be changed from NBP to IIR. Updated files are given further below.
  3. Calculation of isobars for pure fluids at pressures less than the triple point pressure may incorrectly return properties in the liquid phase rather than the vapor phase.
  4. The manual REFPROP9.PDF and the UserInformation sheet in Refprop.xls incorrectly listed isobutene instead of isobutane for R430A. (However, the graphical interface and mixture file are correct.)

Issues with Refprop 9.1

  1. Inputs of enthalpy or entropy may not converge, or will converge to the wrong phase.

Installation Problems.

In some applications where calculations fail after installing versions 9.0 or 9.1, the old DLL from version 7.0 or 8.0 may be hiding in your Windows\System32 directory. Open up this directory and search for Refprop.dll. If you find it, delete it (it should never be stored in the Windows directory). The new one belongs in the Refprop directory along with the executable.

If one of the following error messages appears when the graphical interface is launched:

run-time error 339
component MSHFLXGD.OCX or one of its dependencies not correctly registered:
a file is missing or invalid

or

component COMDLG32.OCX or one of its dependencies not correctly registered:

download the corresponding file from the link below and save it in your Windows\System32 directory on 32 bit machines or to your Windows\SysWOW64 directory on 64 bit machines.

If the error message continues, you will need to register the file by running the appropriate command below for your system and the missing file:

32-bit computers:

regsvr32 c:\Windows\system32\comdlg32.ocx
regsvr32 c:\Windows\system32\mshflxgd.ocx

64-bit computers:

regsvr32 c:\Windows\SysWOW64\comdlg32.ocx
regsvr32 c:\Windows\SysWOW64\mshflxgd.ocx

If an error message occurs referencing the file REFPROP.MSI, try the following: Press your Start button, and then click on "Run …". Type in Regedit. If it does not start at the top of registry, scroll to the top and click on "My Computer". Search for "Refprop 8.1.msi", or whatever msi file it is complaining about in the install error message. You should find something like "HKEY_CLASSES_ROOT\ Installer\ Products\ 6398724E8B370524FA88122E26945D8F". For every occurrence of the item in the registry, you should either rename or delete it. To rename, simply add an underscore in the sequence of numbers, such as "_6398724…". Then try reinstalling the program.

REFPROP is a Program, not a Database Containing Measurements.

The REFPROP "database" is actually a program and does not contain any experimental information, aside from the critical and triple points of the pure fluids. The program uses equations for the thermodynamic and transport properties to calculate the state points of the fluid or mixture. These equations are the most accurate equations available worldwide. A link to one of these equations for R-125 is given below. Their high accuracy is obtained through many coefficients in the equations, and thus the calculation speed will be slower than other equations such as the Peng-Robinson cubic equations. The equations are generally valid over the entire vapor and liquid regions of the fluid, including supercritical states; the upper temperature limit is usually near the point of decomposition of the fluid, and the upper pressure (or density) limit is defined by the melting line of the substance.

Equation of State for HFC-125

Referencing the REFPROP Program in Publications.

The following reference can be used to cite the REFPROP program in publications:

Lemmon, E.W., Huber, M.L., McLinden, M.O. NIST Standard Reference Database 23: Reference Fluid Thermodynamic and Transport Properties-REFPROP, Version 9.1, National Institute of Standards and Technology, Standard Reference Data Program, Gaithersburg, 2013.

Or in BibTeX form:

@Misc{LEMMON-RP91,
  Title                    = {{NIST Standard Reference Database 23: Reference Fluid Thermodynamic and Transport Properties-REFPROP, Version 9.1, National Institute of Standards and Technology}},
  Author                   = {E. W. Lemmon and M. L. Huber and M. O. McLinden},
  Year                     = {2013},
  Doi                      = {http://dx.doi.org/10.18434/T4JS3C},
  Url                      = {https://www.nist.gov/srd/refprop}
}

Additionally, users should cite the reference for either the equation of state or the transport equations used in their work, for example, if you used calculations for CO2, you will find the reference for the equation of state under the Options/Fluid Information option in Refprop and you should cite the reference given under that option, like this:

Span, R. and Wagner, W., J. Phys. Chem. Ref. Data, 25(6):1509-1596, 1996.

Help File

The most recent help file from REFPROP is available below. You should download it to your machine before launching it, otherwise the help file will appear blank.

REFPROP.CHM