density derivative by specific enthalpy
function ddhp extends Modelica.Icons.Function; input Units.SI.Pressure p "pressure"; input Units.SI.SpecificEnthalpy h "specific enthalpy"; input Integer phase = 0 "2 for two-phase, 1 for one-phase, 0 if not known"; input Integer region = 0 "if 0, region is unknown, otherwise known and this input"; output Units.SI.DerDensityByEnthalpy ddhp "density derivative by specific enthalpy"; end ddhp;