How to Install and Set Up NIST REFPROP 9.1 NIST REFPROP 9.1 is a specialized database for calculating the thermodynamic and transport properties of industrially important fluids and mixtures. Released by the National Institute of Standards and Technology (NIST) , version 9.1 introduced key updates like 121 pure fluids and a 64-bit DLL (REFPRP64.dll) for improved integration with modern applications. 1. System Requirements

This happens if the program doesn't know where the /fluids folder is. Go to the REFPROP GUI, select Options > Paths , and ensure the path points to your installation folder.

If you need help with , let me know — I can walk through those as well.

If you have CoolProp installed, you can call REFPROP fluids by setting the "Alternative Path."

: The license file is in the wrong location or has wrong line endings (Unix vs. Windows). Solution : Copy the license file directly into C:\Program Files (x86)\REFPROP\ . Open it in Notepad, save as plain text with ANSI encoding.

Choose unless you have a specific reason not to.