 Enthalpy–entropy chart

An enthalpy-entropy chart, often referred to as a Mollier diagram or H-S diagram, is a graphical representation used in thermodynamics to illustrate the thermodynamic properties of substances, particularly for phase change processes. The x-axis typically represents entropy (S), while the y-axis represents enthalpy (H). These charts are especially useful for analyzing the behavior of gases and refrigerants in various thermodynamic cycles, such as those found in heat engines and refrigeration systems.