derivative function for the specific enthalpy along the phase boundary
function hvl_dp extends Modelica.Icons.Function; input SI.Pressure p "pressure"; input ThermalSeparation.Media.WaterBasedLiquid.BaseClasses.Common.IF97PhaseBoundaryProperties bpro "property record"; output Real dh_dp "derivative of specific enthalpy along the phase boundary"; end hvl_dp;