Water properties base on IAPWS Industrial 1997 http://www.iapws.org/relguide/IF97-Rev.html
The formulation is valid from 273.15 K to 1073.15 K at @100 MPa, and there is a high-temperature region extending to 2273.15 K @50 MPa. There is also a separate equation for metastable steam at pressures up to 10 MPa.
TO_COMPLETE