Approximate method of calculating h_is from upstream properties and downstream pressure
function isentropicEnthalpyApproximation extends Modelica.Icons.Function; input AbsolutePressure p2 "Downstream pressure"; input ThermodynamicState state "Thermodynamic state at upstream location"; output SpecificEnthalpy h_is "Isentropic enthalpy"; end isentropicEnthalpyApproximation;