Vapor Quality from Specific Volume
Find vapor mass fraction in a saturated liquid–vapor mixture.
Try this formula
Calculate vapor mass fraction (quality) or choose another supported quantity.
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Try this formula
Calculate vapor mass fraction (quality) or choose another supported quantity.
Use decimals or scientific notation, such as 1.2e3. Calculations update as you type.
Vapor mass fraction (quality)
Enter the known values to see the result.
The substance is a pure fluid in two-phase liquid–vapor equilibrium. Obtain vf and vg at the same saturation state, using the same mass basis. Require vf ≤ v ≤ vg and vg > vf. Quality is not defined this way for a superheated vapor or subcooled liquid.
Difficulty
Intermediate
Read time
5 min
Prerequisites
Basic algebra and introductory thermodynamics
Source
Teng-Jui Lin — CHEM E 326 — Chemical Engineering ThermodynamicsReference equation: Thermodynamic Properties and Data — Quality. FormuLab wrote new explanations, assumptions, applications, and numerical examples. Made quality a mass fraction with mass-specific volumes. The source also uses molar symbols; mass and molar fractions are not mixed.
Adapted from Teng-Jui Lin, Equation Sheets — Mechanical Engineering Expansion, under CC BY 4.0.
Adapted standard equations and added original lesson text, variables, SI examples, and assumptions. Made quality a mass fraction with mass-specific volumes. The source also uses molar symbols; mass and molar fractions are not mixed.
Definition
A saturated mixture’s specific volume is a mass-weighted average of the liquid and vapor values. Locating the mixture volume between these endpoints reveals its vapor mass fraction.
Variables & Units
| Symbol | Meaning | Units |
|---|---|---|
| Vapor mass fraction (quality) | ||
| Mixture mass-specific volume | ||
| Saturated liquid mass-specific volume | ||
| Saturated vapor mass-specific volume |
Real-World Applications
Steam mixtures
Determine vapor quality from supplied saturated properties.
Property interpolation
Interpret the liquid–vapor lever rule on a mass basis.
Worked Example
Problem
At one saturation state, vf = 0.001 m³/kg and vg = 1 m³/kg. A mixture has v = 0.2008 m³/kg. Find its vapor mass fraction.
Given
Solution
Final Answer
Contents
Info
Tools
Source & review
Reference equation: Thermodynamic Properties and Data — Quality. FormuLab wrote new explanations, assumptions, applications, and numerical examples. Made quality a mass fraction with mass-specific volumes. The source also uses molar symbols; mass and molar fractions are not mixed.
Adapted from Teng-Jui Lin, Equation Sheets — Mechanical Engineering Expansion, under CC BY 4.0.
Adapted standard equations and added original lesson text, variables, SI examples, and assumptions. Made quality a mass fraction with mass-specific volumes. The source also uses molar symbols; mass and molar fractions are not mixed.
Assumptions
- • The substance is a pure fluid in two-phase liquid–vapor equilibrium.
- • Obtain vf and vg at the same saturation state, using the same mass basis.
- • Require vf ≤ v ≤ vg and vg > vf. Quality is not defined this way for a superheated vapor or subcooled liquid.
Languages
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