Enthalpy–entropy chart

An enthalpy–entropy chart, also known as the H–S chart or Mollier diagram, plots the total heat against entropy, describing the enthalpy of a thermodynamic system. A typical chart covers a pressure range of 0.01–1000 bar, and temperatures up to 800 degrees Celsius. It shows enthalpy ${\displaystyle H}$ in terms of internal energy ${\displaystyle U}$, pressure ${\displaystyle p}$ and volume ${\displaystyle V}$ using the relationship ${\displaystyle H=U+pV\,\!}$ (or, in terms of specific enthalpy, specific entropy and specific volume, ${\displaystyle h=u+pv\!}$ ).