Derivative of specific inner energy wrt. pressure at constant specific enthalpy in vapor region for given pressure and specific enthalpy
function du2ph_Ph input Units.SI.AbsolutePressure p "Pressure"; input Units.SI.SpecificEnthalpy h "Specific enthalpy"; output Real duph(unit = "m3/kg") "Derivative of specific inner energy wrt. pressure at constant specific enthalpy"; end du2ph_Ph;