The Mollier diagram is a thermodynamic chart plotting enthalpy against entropy, used to analyze refrigeration cycles and predict system performance. Engineers use this diagram to trace refrigerant state changes through each cycle stage, determining pressure, temperature, and energy values. The Mollier diagram complements psychrometric charts by focusing on refrigerant properties rather than air conditions.
Refrigeration Cycle Analysis
The diagram displays saturation lines, constant temperature lines, and constant pressure lines, allowing technicians to plot compressor inlet, discharge, and expansion valve conditions. A typical vapor compression cycle shows superheated refrigerant entering the compressor, transitioning to high-pressure liquid leaving the condenser, and returning to two-phase mixture in the evaporator. Reading enthalpy values from the diagram reveals system capacity and efficiency losses.
Practical Applications
Technicians reference Mollier diagrams when selecting refrigerants, optimizing superheat and subcooling values, and troubleshooting performance issues. The diagram reveals how compressor discharge temperatures exceed 200°F to 250°F in high-ambient conditions, explaining cooling capacity reductions. Understanding Mollier diagrams helps technicians recognize performance degradation from wear or refrigerant contamination.