Even without a “free REFPROP 10 download 2021,” you have legal low-cost or zero-cost options:
While NIST doesn’t provide a trial for v10 directly, the site sometimes offers a demo for older versions (v9.1). Check the NIST SRD 23 page for current policies. refprop 10 free download 2021
CoolProp is a free, open-source library that implements many EOS from REFPROP (including IF-97 for water and Span-Wagner for CO2). It’s compatible with Python, MATLAB, C++, and Excel. Version 6.4.1 (2021) matches REFPROP 10 accuracy for common refrigerants. Even without a “free REFPROP 10 download 2021,”