Steam quality

Steam quality is the proportion of saturated steam in a saturated water/steam mixture. A steam quality of 0 indicates 100% water while a steam quality of 1 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).

Mathematically, quality is defined by the relationship $x\; =\; mass\; ofvapor/total\; mass$. This can be translated to $x\; =\; (y\; -\; y\; [f]\; )/y\; [fg]$, 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.