Pressure Enthalpy (P-h) Diagram
A Pressure Enthalpy P-h diagram exhibits the same features as a P-n diagram. Figure 11 is the P-h diagram for pure water. A P-h diagram can be constructed for any pure substance.Like the P-n diagram, there are regions on a P-h diagram in which two phases exist together. In the liquid-vapor region in Figure 11, water and steam exist together. For example, at point A, water with an enthalpy (hf), given by point B, exists together with steam with an enthalpy (hg), given by point C. The quality of the mixture at any point in the liquid-vapor region can be found using the following relationship.