Wet Steam Dryness Fraction

Dryness fraction of wet steam, a dimensionless number, is a measure that indicates the proportion of the steam that is in vapor phase (dry) compared to the proportion that is in liquid phase (wet).

Wet Steam Dryness Fraction Interpretation

• \(\zeta = 0\)  -  completely wet or saturated liquid.
• \(\zeta = 1\)  -  completely dry or saturated vapor.

Steam tables or Mollier charts often provide information about the properties of steam, including dryness fraction, at different pressure and temperature conditions.  Engineers and thermodynamicists use dryness fraction to assess the quality of steam in various applications, such as power plants or industrial processes.  High quality dry steam is often desired for efficient energy transfer, while wet steam may lead to issues such as erosion in steam turbines.

 

Wet Steam Dryness Fraction formula
\( \zeta \;=\; w_s \;/\; w_w + w_s \)     (Wet Steam Dryness Fraction) \( w_s \;=\;  - \zeta \; w_w \;/\; \zeta - 1  \) \( w_w \;=\;  w_s ( 1 - \zeta) \;/\; \zeta  \)
Symbol	English	Metric
\( \zeta \)  (Greek symbol zeta) = dryness fraction	\(dimensionless\)	\(dimensionless\)
\( w_s \) = mass of steam	\(lbm\)	\(kg\)
\( w_w \) = mass of water	\(lbm\)	\(kg\)