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In thermodynamics, vapor quality is a quantitative description of the usefulness of a vapor to do mechanical work. The quality of a fluid is the percentage of mass that is vapor;^[1] i.e. saturated vapor has a "quality" of 100%, and saturated liquid has a "quality" of 0%. For instance, in analysis of the Rankine cycle the quality of a multi-phase working fluid would be understood to imply this definition.

Quality $\chi$ can be calculated by dividing the mass of the vapor by the mass of the total mixture:

\chi ={\frac {m_{vapor}}{m_{total}}}

where $m$ indicates mass.

Another definition used by chemical engineers defines quality (q) of a fluid as the fraction that is saturated liquid.^[2] By this definition, a saturated liquid has q = 1. A saturated vapor has q = 0. ^[3]

Calculation

The above expression for vapor quality can be expressed as:

\chi ={\frac {y-y_{f}}{y_{fg}}}

,

where $y$ is equal to either specific enthalpy, specific entropy, specific volume or specific internal energy, $y_{f}$ is the value of the specific property of the substance in the liquid state while under saturated conditions, and $y_{fg}$ is the value of the specific property of the substance in the gas state minus that of the liquid state.

Another expression of the same concept is:

\chi ={\frac {v_{m}}{l_{m}+v_{m}}}

where $v_{m}$ is the vapor mass and $l_{m}$ is the liquid mass.

Steam quality

The genesis 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 drive pistons which create work. The quality of steam can be quantitatively described by steam quality (steam dryness), the proportion of saturated steam in a saturated water/steam mixture.^[4] i.e., a steam quality of 0 indicates 100% water while a steam quality of 1 (or 100%) indicates 100% steam.

The quality of steam on which steam whistles are blown is variable and may affect frequency. Steam quality determines the velocity of sound, which declines with decreasing dryness due to the inertia of the liquid phase. Also, the specific volume of steam for a given temperature decreases with decreasing dryness. ^[5]^[6]

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 enthalpy of water (liquid state).

References

^ Cengel, Yunus A.; Boles, Michael A. (2002). Thermodynamics: an engineering approach. Boston: McGraw-Hill. pp. 91–93. ISBN 0-07-121688-X.
^ Wankat, Philip C. (1988). Equilibrium Staged Separations. Upper Saddle River, New Jersey: Prentice Hall. pp. 119–121. ISBN 0135009685.
^ Perry's Chemical Engineers' Handbook (7th Edition), p 13-29
^ http://www.mines.edu/Academic/chemeng/courses/dcgn210/Handouts/Steam%2520quality.pdf Steam quality
^ Soo, Shao L. (1989). Particulates and Continuum: A Multiphase Fluid Dynamics. CRC Press.
^ Menon, E. Sashi. (2005). Piping Calculations Manual. New York: McGraw-Hill.

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[boles-1] Cengel, Yunus A.; Boles, Michael A. (2002). Thermodynamics: an engineering approach. Boston: McGraw-Hill. pp. 91–93. ISBN 0-07-121688-X.

[2] Wankat, Philip C. (1988). Equilibrium Staged Separations. Upper Saddle River, New Jersey: Prentice Hall. pp. 119–121. ISBN 0135009685.

[3] Perry's Chemical Engineers' Handbook (7th Edition), p 13-29

[4] ttp://www.mines.edu/Academic/chemeng/courses/dcgn210/Handouts/Steam%2520quality.pdf Steam quality

[5] Soo, Shao L. (1989). Particulates and Continuum: A Multiphase Fluid Dynamics. CRC Press.

[6] Menon, E. Sashi. (2005). Piping Calculations Manual. New York: McGraw-Hill.

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@@ Line 1: / Line 1: @@
-:''For inhalation of thermally treated plant material, e.g. tobacco or cannabis, see [[vaporizer]]
+{{For|inhalation of thermally treated plant material, e.g. tobacco or cannabis|vaporizer}}
+{{for|the concept of ''availability'' of thermal energy|exergy efficiency}}
+In [[thermodynamics]], '''vapor quality''' is a quantitative description of the usefulness of a [[vapor]] to do [[mechanical work]]. The quality of a fluid is the percentage of [[mass]] that is [[vapor]];<ref name=boles>{{Cite book  | last1 = Cengel | first1 = Yunus A. | last2 = Boles | first2 = Michael A. | title = Thermodynamics: an engineering approach | date = 2002 | publisher = McGraw-Hill | location = Boston  | isbn = 0-07-121688-X | pages =  91-93}}</ref> i.e. saturated vapor has a "quality" of 100%, and saturated liquid has a "quality" of 0%.  For instance, in analysis of the [[Rankine cycle]] the quality of a multi-phase [[working fluid]] would be understood to imply this definition.
-'''Vapor quality''' is a quantitative description of the usefulness of a [[vapor]] to do [[Mechanical work|work]].  [[Steam engine]]s use water vapor ([[steam]]) to drive pistons which effects work through movement.  The quality of steam can be quantitatively described.
+Quality <math>\chi</math> can be calculated by dividing the mass of the vapor by the mass of the total mixture:
-'''Steam quality''' (steam dryness) is the proportion of [[saturation (chemistry)|saturated]] [[steam]] in a saturated water/steam mixture. A steam quality of 0 indicates 100% water 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 enthalpy of water (liquid state).
+:<math>\chi = \frac{m_{vapor}}{m_{total}}</math>
+where <math>m</math> indicates mass.
+Another definition used by chemical engineers defines quality (q) of a fluid as the fraction that is saturated liquid.<ref>{{cite book|last=Wankat|first=Philip C.|title=Equilibrium Staged Separations|publisher=Prentice Hall|place=Upper Saddle River, New Jersey|year=1988|pages=119–121|isbn=0135009685}}</ref> By this definition, a saturated liquid has q = 1. A saturated vapor has q = 0. <ref>Perry's Chemical Engineers' Handbook (7th Edition), p 13-29</ref>
-Mathematically, quality is defined by the relationship <math>x = mass of vapor/total mass</math>. This can be translated to <math>x = (y - y[f])/y[fg]</math>, where y is equal to either specific enthalpy, specific [[entropy]], [[specific volume]] or [[specific internal energy]]. y[f] is the value of the specific property of the substance in the liquid state while under saturated conditions, and y[fg] is the value of the specific property of the substance in the gas state minus that of the liquid state.
+==Calculation==
-Another possible expression, a different way to write the same, is
+The above expression for vapor quality can be expressed as:
-<math>x_v=\frac{v_m}{l_m + v_m}</math>
+:<math>\chi = \frac{y - y_f}{y_{fg}}</math>,
+where <math>y</math> is equal to either specific enthalpy, specific [[entropy]], [[specific volume]] or [[specific internal energy]], <math>y_f</math> is the value of the specific property of the substance in the liquid state while under saturated conditions, and <math>y_{fg}</math> is the value of the specific property of the substance in the gas state minus that of the liquid state.
+Another expression of the same concept is:
+:<math>\chi=\frac{v_m}{l_m + v_m}</math>
 where <math>v_m</math> is the vapor mass and <math>l_m</math> is the liquid mass.
+==Steam quality==
-The reasoning behind this idea is derived from the origins of [[thermodynamics]]. The most important application of this branch of [[physics]] is the steam engine. Low quality steam would contain a high [[moisture]] percentage and therefore damages the components more easily. High quality steam does not [[corrode]] the steam engine.
+The genesis 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{{cn}}. High quality steam would not [[corrode]] the steam engine. [[Steam engine]]s use water vapor ([[steam]]) to drive pistons which create work. The quality of steam can be quantitatively described by ''steam quality'' (steam dryness),  the proportion of [[saturation (chemistry)|saturated]] [[steam]] in a saturated water/steam mixture.<ref>http://www.mines.edu/Academic/chemeng/courses/dcgn210/Handouts/Steam%2520quality.pdf Steam quality</ref> i.e., a steam quality of 0 indicates 100% water while a steam quality of 1 (or 100%) indicates 100% steam.
 The quality of steam on which [[steam whistle]]s are blown is variable and may affect [[frequency]]. Steam quality determines the [[velocity of sound]], which declines with decreasing dryness due to the [[inertia]] of the [[liquid phase]]. Also, the [[specific volume]] of steam for a given temperature decreases with decreasing dryness. <ref> Soo, Shao L. (1989). Particulates and Continuum: A Multiphase Fluid Dynamics. CRC Press.</ref><ref>Menon, E. Sashi. (2005). Piping Calculations Manual. New York: McGraw-Hill.</ref>
+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 enthalpy of water (liquid state).
 ==References==
 <references/>
-*[http://www.mines.edu/Academic/chemeng/courses/dcgn210/Handouts/Steam%2520quality.pdf Steam quality]
 {{DEFAULTSORT:Vapor quality}}