What does it mean for a fluid to be classified as saturated?

A fluid classified as saturated means that it has reached a state where it contains all the heat it can without undergoing a change in state. In this condition, the fluid is at its boiling point, but it is also in equilibrium between its liquid and vapor phases. This state is characterized by having both liquid and vapor present, which means the fluid is prepared to change its phase from liquid to vapor at any moment if additional heat is added.

When a fluid is saturated, it is at the maximum pressure and temperature for a given substance, and any further increase in heat will cause the fluid to begin to vaporize. This concept is crucial in the context of refrigeration and thermodynamics, as it relates to how heat transfer and phase changes are managed in refrigeration cycles.

Other states, such as complete evaporation or being completely frozen, do not apply to saturated fluids, as these conditions indicate either a change in phase or a lack of heat content relative to the phase transition.