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;