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Chemical Engineering vocabulary · Thermodynamics and Physical Properties

Vapor-liquid equilibrium

Meaning in chemical engineering, with examples

nounCommon term

In chemical engineering, vapor-liquid equilibrium means: The state in which a liquid and its vapor exist together with no net change, each with a fixed composition. It is the basis for designing distillation and flash separations.

In Turkish: buhar-sıvı dengesi

How it is used

Abbreviated VLE. Engineers fit VLE data, choose a thermodynamic model (NRTL, UNIQUAC, Peng-Robinson) in the simulator and plot x-y diagrams. 'Bad VLE data' is a classic reason for a column not meeting spec.

Example sentences

  1. Check the vapor-liquid equilibrium data before trusting the column simulation.

  2. Ethanol and water form an azeotrope, which you can see clearly on the vapor-liquid equilibrium plot.

Common collocations

  • VLE data
  • VLE model
  • x-y diagram
  • binary vapor-liquid equilibrium
  • distillationA way of separating a liquid mixture by boiling it and condensing the vapor, using the fact that the components boil at different temperatures.
  • vapor pressureThe pressure of the vapor above a liquid when the two are in balance at a given temperature. It rises with temperature, and the liquid boils when it equals the surrounding pressure.
  • dew pointThe temperature at which a gas or vapor mixture, when cooled at constant pressure, starts to form the first drops of liquid.
  • boiling pointThe temperature at which a liquid's vapor pressure equals the surrounding pressure, so that it boils. It goes down under vacuum and up at higher pressure.
  • process simulationUsing software to build a computer model of a process, with its equipment, streams and thermodynamics, in order to calculate balances, size equipment and test changes.

More terms: Thermodynamics and Physical Properties

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