Linking REFPROP with Other Applications

Please note:  The information below was developed for Refprop 9.1 (except the VB6 and .NET applications), but in many applications they will still work with Refprop 10.  However, in most cases the new material on Github should be used instead of the applications here when linking with Version 10.

1.      Github website

2.      C Applications

3.      VB6 and .NET Applications

4.      Mac/Unix/Linux Applications

5.      CAPE-OPEN Applications

6.      Perl Applications

7.      MATLAB Applications

8.      Excel Applications


Github website.  The following link will transfer you to the website that documents all new linking applications for Refprop 10:

C Applications.  A sample C++ file comes with the Refprop program and is installed in the Examples directory and explained in the help file.  An example for the C programming language has been written by Ian Bell.  The zip file is included below:


VB6 and .NET Applications.  The following simple application can be used to link Refprop 10 with VB6 (these will not work with Refprop 9.1):


Ian Spanswick provided the following example for linking with VB.NET.  It is based on the VBA code in the Refprop.xls Excel file distributed with Version 10.


Mac/Unix/Linux Applications.  Links to Refprop on Mac, Unix, or Linux operating systems is being developed by Jorrit Wronski, Jean-Baptiste Carre, and Nathan Kamphuis. The application is described at:

CAPE-OPEN Applications.  The following weblink gives the details of a third-party application for linking Refprop to CAPE-OPEN applications.

Perl Applications.  The following example file for the Perl programming language has been written by Chermac Rolle, and he has given us permission to distribute his code to others.


MATLAB Applications.  Keith Wait from GE Home Business Solutions has made the following MATLAB application available.  This application calls the Refprop DLL directly rather than through the mex file provided in previous versions of Refprop.  This release now includes the molar mass, compressibility factor, gross and net heating values, critical point properties, volumetric expansivity, and a number of other properties.  The routines can now read mixture files (*.mix).  When using these new files, be sure to delete the old refpropm.mexw32 or refpropm.mexw64 files if you downloaded them previously.

      refpropm.m (uploaded Oct. 17, 2013)
      Note:  These file names are now lowercase, if you downloaded uppercase versions, delete them before downloading otherwise the case will be changed and the files will not work.
      If an error message such as " not a valid Win32 application" occurs, try downloading the file again, most likely the file was corrupted during the first attempt

For 64-bit MATLAB, the following files should be placed in your Refprop directory:
The files that came with Refprop 8.0 for MATLAB will no longer work with version 2009a.  Chris Muzny of NIST has updated the files and made them available below.

Older files for Refprop 8.0
  2009a 64bit

The zip file below contains both 32 and 64 bit mex files.  These files should work on MatLab 2008a through 2010b. (uploaded April 11, 2012)

Excel Applications.  The Refprop.xls file that comes with the program has Visual Basic (VB) code embedded within it to make the connection between the workbook and the Refprop DLL.  However, when working with anything other than temporary calculations, it is best to start with a blank workbook that does not have the VB code.  In this manner, future updates to the Refprop program can be made available to all of your old workbooks through the instructions below.

If calculations do not appear to work and you are located outside of the U.S., try switching the period and comma, or the comma and semicolon, to enter the numbers in the format required by your version of Microsoft products.  For example, try both of these to see which format is required:

To make the Excel routines in Refprop available to any worksheet in 9.0 (in version 9.1, this is done automatically for you during the installation), two environment variables called RPprefix and Path should be added (you will need administrative rights in order to do this) in a similar manner as shown below in the User variables section:

Do not add these to your System variables section (and more importantly, do NOT damage your path statement in the System variables section!).  In XP, the environment variables can be set under Start/Settings/Control Panel/System/Advanced/Environment Variables, under the "User variables" option.  In Windows 7, this can be found in Start/Control Panel/System And Security/System/Change settings/Advanced/Environment variables.

In 64-bit versions of Windows, Microsoft added another Program Files directory called "Program Files (x86)", which is the default directory where Refprop gets installed.  For the connections to work, you need to either point to this directory in your path statement or copy all the Refprop files to the old "Program Files" directory.

The following outlines the procedure for using REFPROP within any spreadsheet in Office 2007 or 2010:
1.  Open REFPROP.xls and save it as an add-in, REFPROP.xla or REFPROP.xlam, in the main REFPROP folder, C:\Program Files\REFPROP.
2.  Go to File/Options/Trust Center/Trust Center Settings (button at bottom right).
3.  Select "Trusted Locations" on the left.  Click "Add new location".  Browse to C:\Program Files\REFPROP, select "Subfolders of this location are also trusted", and click "OK".
4.  Go to File/Options/Add-Ins and select "Excel Add-ins" in the Manage drop-down box at the bottom, and click Go.
5.  Click "Browse", and navigate to C:\Program Files\REFPROP, select REFPROP.xlam and click OK.  IMPORTANT: Do not simply select REFPROP.xlam when it first comes up, as this will be in the wrong folder (C:\Documents and Settings\Username\Application Data\Microsoft\AddIns), which is not trusted and will not work. 
6.  Select the Data tab, and click on Edit Links.  Select REFPROP.xlam.  Click on Change Source and navigate to C:\Program Files\REFPROP.  Select REFPROP.xlam there and click OK.  (This is just to make sure you are connected to the correct Add-in.)  If the Data tab is greyed out, start typing in a Refprop command [such as “=Density("water","TP","SI",300,1) ] and the button should become active.
7.  Once you have the xla or xlam file set up, you can open a brand new work book and the functions should be available to you.  Do not continue working with the Refprop.xls file since it still contains the VB code that is also in the xlam file.  In this manner, future updates from NIST of the Refprop.xls file can be resaved as the xlam file, and all of your work books will have access to the most recent code.

Other tips:
1.  In some cases the macros may not work.  Try saving the file as a macro-enabled workbook (under Save As…).
2.  The xls file distributed with version 9.0 sometimes will give false answers depending on the sequence of calculations if multiple xls files are open.  Switching between the open files may cause the initial setup to be lost.  The updated xls file given above fixes this.
3.  For inputs that do not required a 5th parameter, Excel may require the comma at the end, for example:   =Pressure("water", "TVAP", "SI", 298,)
4.  If Excel cannot find the Refprop fluid files, you can copy the *.FLD and HMX.BNC files into a default directory:  C:\REFPROP\FLUIDS.  When the program fails to find the fluid files, it will look to see if a C:\REFPROP\FLUIDS (or D:) is available, and if so it will use the files from that source.
5.  If you see dual entries for each function in your workbook, then you have either saved two xla files, or you are working with a file that still contains the VB code.  Start with a blank workbook to eliminate the dual entries for the latter case.

There have been a number of users who have had problems with the Excel link to Refprop.  In some of these cases and in other situations we have found that the refprop.dll file had also been installed in either the c:\windows directory or the c:\windows\system32 directory.  If you experience problems, please do a full hard drive search for refprop.dll and delete all occurrences except the one in your c:\program files\refprop directory.

Last modified: February 4, 2019