Returns the specific enthalpy.
The function is based on Modelica.Media.Water.WaterIF97_base.specificEnthalpy_pT. However, for the typical range of temperatures and pressures encountered in building and district energy applications, a linear function sufficies. This implementation is therefore a linear surface fit of the IF97 formulation h(p,T) in the ranges of 100°C ≤ T ≤ 160°C and 100 kPa ≤ p ≤ 550 kPa. The fit is scaled by the dataset's mean and standard deviation values to improve conditioning. The largest error of this linearization is 2.42 kJ/kg (0.09%), which occurs at 100.6°C and 100 kPa. The root mean square error (RMSE) is 0.76 kJ/kg.