The Pressure-Enthalpy Diagram is perfect for graphical representations of states of fluids. It allows to show, how thermodynamic processes are working with changes of states. That's the main reason for its widely usage in refrigeration and heat pump business.
This video part shows you, which type of information is contained in those diagrams.

chapters:
00:18 - Why?
00:34 - The Axes of the Diagram
01:51 - Specific Enthalpy h (Isenthalpic Line)
02:14 - Pressure p (Isobaric Line)
03:13 - Between the Axes
04:02 - The Two-Phase Domain
05:17 - Temperature T (Isothermal Line)
05:54 - Specific Volume v (Isochoric Line)
06:22 - Specific Entropy s (Isentropic Line)

Diagrams generated with "CoolPack":
http://www.en.ipu.dk/Indhold/refriger...