Interactive Self-Study Module: Water-Air Vapor-Liquid Equilibrium and Psychrometric Chart


This module uses screencasts and an interactive simulation to discuss vapor-liquid equilibrium for water in the presence of air. It explains how to use a psychrometric chart (humidity chart). It then provides example problems to allow the user to test themselves. Your retention of material in this module will increase if you write down reasons for your answers to ConcepTests, questions in screencasts, and questions to answer before using interactive simulations, and you try to solve the example problems before watching the screencast solutions. We suggest using the learning resources in the following order:

  1. Attempt to answer the multiple-choice ConcepTest and solve the example problem before watching the screencasts or working with the simulations.
  2. Watch the screencasts that explain psychrometric charts and humidity.
  3. Review important equations for this topic.
  4. Use the interactive simulation to further understand psychrometric charts.
  5. Try to solve the example problems before watching the solutions in the screencasts.
  6. Answer the ConcepTests.
  7. Look at the list of key points, but only after you try to list the key points yourself.
  • Vapor-liquid equilibrium for water and humidity are important in many applications.
  • This module is intended for a thermodynamics course or a materials and energy balances course.
Before studying this module, you should be able to:
After studying this module, you should be able to:
  • Use a psychometric chart to determine dry bulb temperature, wet bulb temperature, dew point temperature, relative humidity, and enthalpy.
  • Predict behavior of two-phase systems with two components where only one component is in the liquid phase (air/water systems).
  • Apply energy balances to vapor liquid equilibrium for air/water systems.
  • Apply mass balances two air/water systems equilibrium.
  • Use steam tables to determine equilibrium conditions for air/water systems.