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-   -   Evaporation of a species (http://www.cfd-online.com/Forums/fluent/41800-evaporation-species.html)

ling July 20, 2006 10:40

Evaporation of a species
 
Hello,

Does anyone know who to do evaporation ? For example, some solid particles (not very soluble) are mixed in water. They then float on the surface of water and evaporate into air as they are highly volatile. Evaporation, or mass transfer rate can be considered to be first order with respect to the concentration of the substance in this case.

Have been looking through in and out of help manuals in vain. Please help !

ling

tomek July 20, 2006 15:44

Re: Evaporation of a species
 
i don`t thing it is possible to evaporate solid species from water surface. But..... I assume you are using VOF model (you should if you have a interphase surface - free surface). Try with mass transfer example (udf user guide). In MASS_TRANSFER udf you can establish phases and species and mass trenasfer from phase, from species to phase to species. I saw such udf on this forum. By Greg or someone else. I tried to do it by myself but it doesn`t work. I`ve heard it is impposible. If you will menaged to do it let me know. tomek

ling July 21, 2006 11:15

Re: Evaporation of a species
 
hey ... thanks for your reply ! yes, I am trying to do Mass_Transfer UDF. But even before that, I have 2 problems. I am thinking of making Camphor a fluid, then use Species/Transport and Multiphase module. However, firstly, I have problems with the boundary condition of the free surface. I do not know what to specify since I will be using the Mass_Transfer UDF. Secondly, I have also been trying to 'Patch' the initial condition of the 2 regions: namely, the water phase and the air phase. But it did not give me a pure water region or a pure air phase region, but rather something of a gradient.

Any suggestions ? I would appreciate any piece of info/advice !! Thanks.

tomek July 21, 2006 12:19

Re: Evaporation of a species
 
I don`t know how you model looks like but to establish BC for free surface as i remember you need to set up a surface tension in phase panel/ interaction beetwen phases. In the same panel you set up a mass transfer. You can find a VOF tutorial on web - it will help you to set up other parameters.... secondly - patching. if you have a 2D model go to adapt and region and than mark a region of your gas or liquid phase. I suggest you (If you geometry allow you to do it) to patch both regions (liquid and gas). Than go to initialize/patch choose on of the registers in register to patch (but remeber what is phase and what is gas region - or what should be:)) and mark it. In phase panel (on left side of window) choose an appropriate phase (don`t choose a mixture!). Than you need to enter 1 in value panel. Done (I hope so:))

tomek July 21, 2006 12:54

Re: Evaporation of a species
 
read it

http://www.fluentusers.com/support/u...multiphase.pdf


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