Specific Enthalpy of air. Specific enthalpy is defined as jouleskg or kilojouleskg. A Mathematical Derivation Of The Equations Relating The Pressure Temperature And Volume During An Isen Engineering Notes Physics Lessons Sixth Grade Science Specific enthalpyh is defined as huPν where u is the specific internal energy Btulbm of the system being studied P is the pressure of the system lbfft 2 and ν is. . Specific Enthalpy of Steam Water System. The figures and tables below shows how water enthalpy and entropy changes with temperature C and F at water. Assuming constant pressure conditions the specific enthalpy of dry air can be. The most basic way to calculate enthalpy change uses the enthalpy of the products and the reactants. It is genrally the sum of. Please note that enthalpy is the measure of the total heat content of the system whereas specific enthalpy is equivalent to the sum of specific Internal energy and the.