Mass fraction of a saturated mixture which is vapor
For inhalation of thermally treated plant material, e.g. tobacco or cannabis, see Vaporizer (inhalation device). For the concept of availability of thermal energy, see Exergy efficiency.
Quality χ can be calculated by dividing the mass of the vapor by the mass of the total mixture:
where m indicates mass.
Another definition used in chemical engineering defines quality (q) of a fluid as the fraction that is saturated liquid.[2] By this definition, a saturated liquid has q = 0. A saturated vapor has q = 1.[3]
An alternative definition is the 'equilibrium thermodynamic quality'. 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):
Subscripts f and g refer to saturated liquid and saturated gas respectively, and fg refers to vaporization.[4]
Calculation
The above expression for vapor quality can be expressed as:
where is equal to either specific enthalpy, specific entropy, specific volume or specific internal energy, 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 and vapor .
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.[citation needed] High quality steam would not corrode the steam engine. Steam engines use water vapor (steam) to push pistons or turbines, and that movement creates work. The quantitatively described steam quality (steam dryness) is the proportion of saturated steam in a saturated water/steam mixture. In other words, a steam quality of 0 indicates 100% liquid, while a steam quality of 1 (or 100%) indicates 100% steam.
Steam quality is very useful in determining enthalpy of saturated water/steam mixtures, since the enthalpy of steam (gaseous state) is many orders of magnitude higher than the enthalpy of water (liquid state).
^Perry's Chemical Engineers' Handbook (7th Edition), p 13-29
^Ghiaasiaan, S. Mostafa (2008). Two-phase flow, boiling and condensation in conventional and miniature systems. New York: Cambridge University Press. p. 96. ISBN978-0-521-88276-7.
^Soo, Shao L. (1989). Particulates and Continuum: A Multiphase Fluid Dynamics. CRC Press.
^Menon, E. Sashi. (2005). Piping Calculations Manual. New York: McGraw-Hill.