Vapor quality is an intensive property which can be used in conjunction with other independent intensive properties to specify the thermodynamic state of the working fluid of a thermodynamic system.
It has no meaning for substances which are not saturated mixtures (for example, compressed liquids or superheated fluids).
Working fluids can be classified by using the appearance of droplets in the vapor during the expansion step.
Another definition used in chemical engineering defines quality (q) of a fluid as the fraction that is saturated liquid.
It can be used only for single-component mixtures (e.g. water with steam), and can take values < 0 (for sub-cooled fluids) and > 1 (for super-heated vapors): where h is the mixture specific enthalpy, defined as: Subscripts f and g refer to saturated liquid and saturated gas respectively, and fg refers to vaporization.
is the value of the specific property of saturated liquid state and
is the value of the specific property of the substance in dome zone, which we can find both liquid
The origin of the idea of vapor quality was derived from the origins of thermodynamics, where an important application was the steam engine.
Low quality steam would contain a high moisture percentage and therefore damage components more easily.
Steam quality determines the velocity of sound, which declines with decreasing dryness due to the inertia of the liquid phase.