Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Modeling evaporation

  1. May 19, 2014 #1
    Hi there!

    My first post, exciting. What I'm after is a little help steering me in the right direction. I'm attempting to model evaporation in a closed system, and I'm not sure how to go about it. That is, lets assume we have a liquid in a partially filled container, and the rest is filled with vacuum initially just to make things easier. The container is sealed and no heat is able to enter the system.

    The liquid is below its vapour pressure, so evaporation will happen, pressurising the container until an equilibrium point is reached. The equilibrium point can be worked out algebraically--easy enough. What I'm interested in, however, is modelling the transients. That is, evaporation will cause a localized temperature drop near the surface of the liquid owing to the latent heat of evaporation of the liquid, and this cooler fluid will in turn set up some natural convection in both phases I'm assuming. As well, the net decrease in temperature will cause the vapour pressure of the liquid to decrease as well, causing more evaporation and more pressure in the gas-filled portion of the vessel. Etc. etc...

    So let's say I have well defined thermophysical information about the fluid, what I'm wondering is where I can find some information about the mechanics of the process beyond the hand-waving I've done in the previous paragraph? Ultimately, I'd like to model this situation numerically and include heat transfer from the vessel, but the first part is developing said model.

    Google has led me to a number of articles about modeling of boiling, which is a little more resolution than what I think I need at this point (especially as those sorts of systems are notoriously difficult to simulate) and was hoping there may be something more accessible out there.

    This is a little outside my normal area of work, hence why I'm a bit lost as to what to search for.
  2. jcsd
  3. May 20, 2014 #2


    User Avatar
    Science Advisor

    At equilibrium, there will be exchange of energy only at the phase interface. I see no reason why circulation will continue in the gas or the liquid after equilibrium is reached. Without external energy, there will be no energy to drive circulation, so the shape of the container and the circulation modes or patterns will not be important in energy distribution.

    Boiling is a quite different energy transfer situation, where heat is supplied at the bottom of the liquid, that energy is convected or radiated to be lost from the top of the system. With boiling the shape of the container and geometry of heat flow would be very important.
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook