Refprop does not return correct derivatives in the two-phase region. There are ways to calculate the correct values from saturation properties, especially for density. An if-clause should be used to determine the fluid state and adapt the calculation procedure if needed.
The currently implemented numerical derivatives are neither accurate nor fast... Check refprop_wrapper.cpp around line 1020 to see the implementation.
Refprop does not return correct derivatives in the two-phase region. There are ways to calculate the correct values from saturation properties, especially for density. An if-clause should be used to determine the fluid state and adapt the calculation procedure if needed.
The currently implemented numerical derivatives are neither accurate nor fast... Check refprop_wrapper.cpp around line 1020 to see the implementation.