saturation vapor curve

{{short description|Curve separating the two-phase and superheated states of a T-s diagram}}

{{too technical|date=December 2023}}

In thermodynamics, the saturation vapor curve is the curve separating the two-phase state and the superheated vapor state in the T–s diagram (temperature–entropy diagram).

The saturated liquid curve is the curve separating the subcooled liquid state and the two-phase state in the T–s diagram.{{usurped|1=[https://web.archive.org/web/20110619010045/http://www.learnthermo.com/T1-tutorial/ch07/lesson-B/pg08.php A New Phase Diagram: The T-S Diagram]}} at LearnThermo.com

When used in a power cycle, the fluid expansion depends strongly on the nature of this saturation curve:

• A "wet" fluid shows a negative saturation vapor curve. If overheating before the expansion is limited, a two-phase state is obtained at the end of the expansion.

:File:Wet_fluid.png

• An "isentropic" fluid shows a vertical saturation vapor curve. It remains very close to the saturated vapor state after an hypothetical isentropic expansion.

:File:Isentropic_fluid.png

• A "dry" fluid shows a positive saturation vapor curve. It is in dry vapor state at the end of the expansion, and strongly overheated.

:File:Dry_fluid.png