The pressure-enthalpy diagram, also known as a log P/h diagram, is a graphical representation of the thermodynamic properties of a refrigerant. It plots the pressure of the refrigerant against its enthalpy, allowing technicians, engineers, and researchers to visualize the refrigerant’s behavior during different stages of the refrigeration cycle. This diagram is essential in refrigeration systems as it enables the analysis of system performance, identification of potential issues, and optimization of system design and operation.