Compressed fluid

A P-v diagram for liquid water. The compressed fluid region is located to the left of the blue line (the liquid-vapor phase boundary).

A compressed fluid (also called a subcooled fluid or subcooled liquid) is a fluid under mechanical and or thermodynamic conditions that force it to be a liquid. It is a liquid at a temperature lower than the saturation temperature at a given pressure. In a plot that compares absolute pressure and specific volume (commonly called a P-v diagram), of a real gas, a compressed fluid is to the left of the liquid-vapor phase boundary; that is, it will be to the left of the vapor dome.

Conditions that cause a fluid to be compressed include:

• Specific volume less than the specific volume of a saturated liquid
• Fluid temperature below the saturation temperature
• Pressure above the saturation pressure
• Enthalpy smaller than the enthalpy of a saturated liquid

The term compressed liquid emphasizes that the pressure is greater than the saturation pressure for the given temperature. Compressed liquid properties are relatively independent of pressure. As such, it is usually acceptable to treat a compressed liquid as a saturated liquid at the given temperature.

See also

• Gas cylinder