Graphical Dew, Bubble, and Flash Reference Page
Show Some Flash and Dew the Dew with a Little Bubbly!

Author

DOFPro group

  • Video links go directly to the YouTube video.
  • JTF (Just the Facts) videos are the streamlined versions: greenscreen LaTeX equations, clean graphics, minimal narrative. Think efficient and to the point. Each has a companion TFS video.
  • TFS (The Full Story) videos include interviews, additional explanation, and equations written on whiteboards. Same math, more context, more personality. Each has a matching JTF version.
  • Info Page links lead to definitions, expanded explanations, and related material—because sometimes you really do need to explain it.
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Intro to Graphical Dew, Bubble, and Flash Calculations

When a liquid mixture is heated or a vapor mixture is cooled, the system may enter a two-phase region where both liquid and vapor are present. Calculating the conditions where these phase changes begin or determining the compositions of the resulting phases is an important task in chemical engineering.

The videos on this page explain how bubble points, dew points, and flash calculations can be determined graphically using phase diagrams.

Show Some Flash and Dew the Dew with a Little Bubbly!

This video demonstrates how graphical phase diagrams can be used to determine bubble pressures, dew pressures, bubble temperatures, dew temperatures, and flash conditions.

Visuals

Examples and Definitions

Definitions

Dew Pressure
The pressure at which a vapor of known composition and temperature first begins to condense. The composition of the first liquid formed is usually determined as part of the calculation.
Bubble Pressure
The pressure at which a liquid of known composition and temperature first begins to vaporize. The composition of the first vapor formed is usually calculated.
Dew Temperature
The temperature at which a vapor of known composition and pressure first begins to condense.
Bubble Temperature
The temperature at which a liquid of known composition and pressure first begins to vaporize.
Flash
A process in which a mixture with a known overall composition is brought to a specified temperature and pressure within the two-phase region. The mixture separates into vapor and liquid phases, and the phase compositions and phase amounts are determined.
Azeotrope
A mixture composition at which the vapor and liquid phases have identical compositions at a given temperature and pressure. Because of this property, azeotropes cannot be separated by simple distillation.