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Old   February 10, 2010, 03:36
Default Oxygen mass transfer
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Luis Cea
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Hello,

I am trying to model the mixing of oxygen and water in a mixing vessel. I am considering 2 phases and 3 components. The liquid phase is a mixture of water and dissolved oxygen, and the gas phase is pure oxygen. I would like to include the mass transfer from pure oxygen (gas phase) to dissolved oxygen (liquid phase), but cannot find any tutorial which indicates how to do this. The tutorials I have related to mixing vessels do not consider the mass transfer between the gas and liquid phases.
Can anyone help with this or give any hint?

many thanks,
Luis
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Old   February 10, 2010, 05:27
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You will need to contact CFX support for examples of advanced simulations like this.
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Old   February 10, 2010, 07:36
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Idtisak Paopo
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Quote:
Originally Posted by lcea View Post
Hello,

I am trying to model the mixing of oxygen and water in a mixing vessel. I am considering 2 phases and 3 components. The liquid phase is a mixture of water and dissolved oxygen, and the gas phase is pure oxygen. I would like to include the mass transfer from pure oxygen (gas phase) to dissolved oxygen (liquid phase), but cannot find any tutorial which indicates how to do this. The tutorials I have related to mixing vessels do not consider the mass transfer between the gas and liquid phases.
Can anyone help with this or give any hint?

many thanks,
Luis
I am using CFX v.11. For the quick suggestion, you can define each phase with its components like O2 in air then O2l in liquid phase and you can link these 2 components with Henry's law. All can be done in CFX v. 11 but it will consume lot of time to simulate. Now I consider only O2 but I need to run it on a cluster so you need to consider about your computer capacity as well.
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Old   February 10, 2010, 10:54
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Many thanks for your help.
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Old   November 25, 2019, 05:41
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Originally Posted by Idtisak View Post
I am using CFX v.11. For the quick suggestion, you can define each phase with its components like O2 in air then O2l in liquid phase and you can link these 2 components with Henry's law. All can be done in CFX v. 11 but it will consume lot of time to simulate. Now I consider only O2 but I need to run it on a cluster so you need to consider about your computer capacity as well.
How I can simulate the change of disolved oxygen in wáter depending on temperatura?
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Old   November 25, 2019, 06:11
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You need to model this with 2 phase flow. For O2, you need interphase mass transfer and Henry coefficient.
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Old   November 25, 2019, 06:24
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You need to model this with 2 phase flow. For O2, you need interphase mass transfer and Henry coefficient.
Hi again and thanks for your response..

I want to modelate the oxygen disolved in wáter depending on temperature. I use the Eulerian model and (wáter for primary phase and oxygen for secondary phase) and I actívate species transport. Then I actívate the Henry's law. I dont know if what I am doing is correct… Do you know any idea?

What do you want to say with interphase mass transfer?

Thank you
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Old   November 25, 2019, 06:31
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interphase mass transfer is from one phase to the other. So, from liquid water to gas oxygen. Perfectly fine.
In order to include the dependency from temperature, you need to make the henry coefficient a function of temperature.


Do you have pure oxygen?
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Old   November 25, 2019, 06:36
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Originally Posted by Gert-Jan View Post
interphase mass transfer is from one phase to the other. So, from liquid water to gas oxygen. Perfectly fine.
In order to include the dependency from temperature, you need to make the henry coefficient a function of temperature.

Do you have pure oxygen?
Okey, so I need an UDF to specify the henry coefficient depending on temperatura?

Yes, I wnt to know only the change of disolved oxygen in water. I know that the oxygen disolved in water decrease with temperatura so I want to modelate this but only taking into account two phases water and oxygen. So I put water in the primary phase (volumen fraction = 1) and oxygen in the secondary phase (volumen fraction = 0) in the starting point. Then I want to see that the oxygen quantity change because of the temperatura.
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Old   November 25, 2019, 06:44
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1) A UDF? Haven't used that in the past 10 years.
You just create an expression for H as a function of temperature and in Pre use that expression where you give in the value for the Henry coefficient.

2) sounds like this is normal water and air, not? So what about nitrogen? You need to include that as well.

3) main challenge will be the initial bubble size. Do you already have any idea about that?
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Old   November 25, 2019, 06:59
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Originally Posted by Gert-Jan View Post
1) A UDF? Haven't used that in the past 10 years.
You just create an expression for H as a function of temperature and in Pre use that expression where you give in the value for the Henry coefficient.

2) sounds like this is normal water and air, not? So what about nitrogen? You need to include that as well.

3) main challenge will be the initial bubble size. Do you already have any idea about that?
How you créate this expression?
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Old   November 25, 2019, 07:10
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Are you a newbie? Haven't done any tutorial or similar?

Nevertheless, in Pre, just create an expression (it is in the tree). Something like H=1e3[Pa/K]*T
Make sure the units are correct.
And then use that expression, where you used the value for the Henry coefficient (click on the expression icon, then use the Right Mouse button, to look up your expression).
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