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Someone knows how to configure transport of diluted species?

Posted Feb 14, 2015, 4:20 p.m. EST Chemical Reaction Engineering Version 4.4 5 Replies

Houari Cobas
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Hello, someone knows how to configure transport of diluted species?
I`m trying to simulate the diffusion of methanol in water. My model have two inputs and an output, microchannels. My question is i have to define the concentration of methanol and concentration of water at their respective model inputs or i have to define the methanol concentration and leave the water as 0?

thank you very much
5 Replies Last Post Feb 17, 2015, 2:29 p.m. EST
Lasse Murtomäki
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Posted: 10 years ago Feb 14, 2015, 11:32 p.m. EST
Hi

If you are using Transport of Diluted Species module you have only one diffusing species, methanol. You do not need to consider water in the diffusion node, but naturally you have to solve the flow profile (if you have convection).

But if you have a methanol-water mixture with substantial concentration of methanol, you should use the concentrated species module. There you define the mole fractions of the species.

br
Lasse
Hi If you are using Transport of Diluted Species module you have only one diffusing species, methanol. You do not need to consider water in the diffusion node, but naturally you have to solve the flow profile (if you have convection). But if you have a methanol-water mixture with substantial concentration of methanol, you should use the concentrated species module. There you define the mole fractions of the species. br Lasse
Houari Cobas
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Posted: 10 years ago Feb 15, 2015, 12:00 a.m. EST
Thank you very much Lasse.
In my problem i have two channels, one with water and another one with methanol. Those channels will met in a certain point and then the methanol will diffuse in water. That`s what i want to simulate. So taking into account what you told me, i just have to specify the methanol concentration that would be 24.7e3 mol/m^3. That`s rigth?
As part of the simmulation i had ressolved the flow problem before.

thanks you very much
Houari
Thank you very much Lasse. In my problem i have two channels, one with water and another one with methanol. Those channels will met in a certain point and then the methanol will diffuse in water. That`s what i want to simulate. So taking into account what you told me, i just have to specify the methanol concentration that would be 24.7e3 mol/m^3. That`s rigth? As part of the simmulation i had ressolved the flow problem before. thanks you very much Houari
Lasse Murtomäki
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Posted: 10 years ago Feb 16, 2015, 1:59 a.m. EST
OK

That is a different problem altogether. Have you checked Comsol model library on this site? My previous reply does not apply.

br
Lasse
OK That is a different problem altogether. Have you checked Comsol model library on this site? My previous reply does not apply. br Lasse
Tobias K
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Posted: 10 years ago Feb 17, 2015, 8:02 a.m. EST
Dear Houari Cobas ,

I was wondering how do you set the concentration when you have a flow going on? Do you just set that concentration as an initial condition in the domain or do you specify your inflow?

Thx.
Best,
Tobias
Dear Houari Cobas , I was wondering how do you set the concentration when you have a flow going on? Do you just set that concentration as an initial condition in the domain or do you specify your inflow? Thx. Best, Tobias
Houari Cobas
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Posted: 10 years ago Feb 17, 2015, 2:29 p.m. EST
First of all, thank you very much for your answers.
Well in my problem I have this two channels that will find each other in a third channel. in the last one is where the diffusion will take place. I had defined one of the first two channels as is methanol flowing on it. The other and the third one I defined as water. I am really not simulating the channel itself but the liquids flowing trough it.
At the methanol channel entrance I defined the methanol concentration of 24700 mol/m^3. Not as an initial condition but as a boundary condition. As Lasse sugest I not defined any concwntration at the water entrance.
the problem first solve the fluid flow problem and then the chemical problem. What I am looking is at the diffusion profile in the third channel once the two liquids find each other.
Like I am not chemist I am wondering if this simmulation should be settled this way or if it is wrong.
I saw mixers examples. They define an input with a half of it with certain concentration and the other half with 0 concentration. But the concentration they use is something like 10 mol/m^3 or in that orther. In my case I calculated the amoun of mol in a m^3 which is 24700.
Can you tell me if I am doing it rigth or wrong? If I am wrong can you wive an advice about how to correct my errors?
Thank you very much
Houari
First of all, thank you very much for your answers. Well in my problem I have this two channels that will find each other in a third channel. in the last one is where the diffusion will take place. I had defined one of the first two channels as is methanol flowing on it. The other and the third one I defined as water. I am really not simulating the channel itself but the liquids flowing trough it. At the methanol channel entrance I defined the methanol concentration of 24700 mol/m^3. Not as an initial condition but as a boundary condition. As Lasse sugest I not defined any concwntration at the water entrance. the problem first solve the fluid flow problem and then the chemical problem. What I am looking is at the diffusion profile in the third channel once the two liquids find each other. Like I am not chemist I am wondering if this simmulation should be settled this way or if it is wrong. I saw mixers examples. They define an input with a half of it with certain concentration and the other half with 0 concentration. But the concentration they use is something like 10 mol/m^3 or in that orther. In my case I calculated the amoun of mol in a m^3 which is 24700. Can you tell me if I am doing it rigth or wrong? If I am wrong can you wive an advice about how to correct my errors? Thank you very much Houari

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