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Old   February 10, 2006, 09:14
Default Multiphase reaction...
  #1
Rishi
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I am trying to model the rise of a single gas bubble ( Co2 in NaOH ... which model is best suited for this and how do I specify reaction ???
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Old   February 13, 2006, 03:45
Default Re: Multiphase reaction...
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Kharicha
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Do you have a mass transfer from the sourrounding liquid to the bubble ?
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Old   February 13, 2006, 12:25
Default Re: Multiphase reaction...
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Rishi
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ya... co2 is rising in NaOH with reaction ... so which model will be best suited for this purpose.
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Old   February 14, 2006, 01:57
Default Re: Multiphase reaction...
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Kharicha
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To choose a model i need much more details about what you want to do.

I am not supposed to know the reaction, what is converted in what....

There are two possibilities,

eitheir your reaction takes place with with small concentration and creates elements wich are not one of the two phases,

either the reactions takes place between the two phases, and the results are strictly equal to one of the two phases....

So please detail a bit...
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Old   February 15, 2006, 00:52
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Rishi
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ok.. the basic reaction taking place is

NaOH + CO2 -> Nahco3 NaOH is 4% in conc. and the single gas bubble is rising in the solution and thereby there is a decrease in the radius of the gas bubble. I have to model the decrease in radius of this gas bubble.

I would be thankful if you are able to help. you can mail me for any further clarification at rishi_iitkgp@yahoo.co.in
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Old   February 15, 2006, 02:12
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Kharicha
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Now it is clear....

For this you need to use a VOF model. You can model the reaction by writing an UDF for a mass transfer from the bubble to the surrounding flow.

so define two phases, one gas and one liquid. The mass transfer is from the gas to liquid.

If your reaction takes place at the surface of the bubble and is not function of a varying concentration, your mass transfer will be simple to write.

But if it depends on a concentration (in the liquid I assume)then you have to add an Userdefined scalar equation which will model the concentration field.

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Old   February 15, 2006, 04:38
Default Re: Multiphase reaction...
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Rishi
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Thanx... but the thing is I have to assume constant mass transfer rate so its ok. Also where do I specify the reaction part? will defining diffusivity constant in the Interaction of Multiphase suffice?

solver >> Multiphase >> Inetraction>> mass transfer

do you have any references ( URL or book ) which could help us.
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Old   February 15, 2006, 16:58
Default Re: Multiphase reaction...
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grzesiek
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hi your suggestion is very useful for me becouse I have the same problem . But what to do if mass transfer depends of concetration of solution (fluid) and takes place in whole volume of fluid? not only at surface? regards Grzesiek
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