In a cold chain, a container carries cold in prepared coolant instead of producing it. A phase change material can absorb energy as it changes from solid to liquid; during the transition, some energy goes into the change of state rather than raising temperature. This storage is called latent heat.
The transition on a temperature curve. A material's temperature changes as it exchanges energy before and after a phase change. During the transition, it may change more slowly around its melting or freezing point. That section of a plate's graph alone does not prove the container interior stays at the same temperature; the load, insulation and surroundings also need measurement.
Choose a plate for the load. The plate's transition temperature should match the range the load must maintain. When comparing plates with different melting points, check the product target against the manufacturer's phase-change data for the specific model. A plate name or its lowest temperature alone is not a selection criterion.
During a shipment trial, log product temperature and plate condition along the route. This shows how the phase change supports the actual load; do not generalize one model's capacity figure to another.
