Specific Enthalpy

The Specific enthalpy (h) is stated as h = u + Pν, here u is the specific internal energy (Btu/lbm) of the system being considered, P is the pressure of the system (lbf/ft²), and ν is the specific volume (ft³/lbm) of the system. The enthalpy is generally used in connection with an "open" system dilemma in thermodynamics. The enthalpy is a property of a substance, such as temperature, pressure, and volume, though it cannot be measured directly. Generally, the enthalpy of a substance is provided with respect to several reference values. For illustration, the specific enthalpy of water or steam is given by using the reference which the specific enthalpy of water is zero at .01°C and ordinary atmospheric pressure. The information that the absolute value of specific enthalpy is unidentified is not a problem, though, since it is alter in specific enthalpy (?h) and not the absolute value which is significant in practical problems. The steam tables involve values of enthalpy as portion of the information tabulated.