Enthalpy-Temperature (h-T) Diagram

The h-T diagram displays similar features as on the earlier property diagrams. The figure below is an h-T diagram for pure water. The h-T diagram can be built for any pure substance. Since in the property diagrams, there are areas on the h-T diagram in which two phases exist altogether. The area among the saturated liquid line and the saturated vapor line symbolizes the region of two phases existing at similar time. The vertical distance among the two saturation lines symbolizes the latent heat of vaporization. When pure water existed at point A on the saturated liquid line and a quantity of heat was added equivalent to the latent heat of the vaporization, then the water would alter phase from a saturated liquid to a saturated vapor (i.e., point B), whereas maintaining a constant temperature. As shown in figure shown below, operation exterior to the saturation lines outcomes in a subcooled liquid or superheated steam.

Figure: h-T Diagram for Water

The quality of the mix at any point in the liquid-vapor area can be found by using the similar relationship as shown in the P-h diagram above.