returns density for given p and h
function density_phX extends Modelica.Icons.Function; input AbsolutePressure p "Pressure"; input SpecificEnthalpy h "Enthalpy"; input MassFraction X[nX] "Mass fractions"; input Integer phase = 1 "2 for two-phase, 1 for one-phase, 0 if not known"; output Density d "density"; end density_phX;