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-   -   Mixing of air and CO2 (https://www.cfd-online.com/Forums/cfx/91858-mixing-air-co2.html)

 unischlaf August 24, 2011 16:36

Mixing of air and CO2

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Hi, I have no experience with CFX Pre. So I hope someone can help me. I would like to calculate the mixing of CO2 after a nozzle with air. In the sketch you can see the construction.

I have 2 meshes. One for die nozzle and one for the pipe. Therefore there is a interface at the end of the nozzle (red marked).

Now my question: What I have to set in CFX Pre for both domains? In the domain of the lance I have set "CO2 ideal gas" (calorically perfect ideal gas) as material. I think that's right. But what should I set in the other domain? Is it enough to set "ideal gas" as material. Or do I consider CO2 as material?

Can someone tell me the correct settings, please? Thank you!

 ghorrocks August 24, 2011 18:46

No need for multiple domains. Just use a single domain. Use a multicomponent gas if you want to fully model the mixing process, but you could simplify this model down to a single component (ie air) and add the CO2 as an additional variable if you like. This is much simpler, but does not take into account the full fluid property changes due to mixture composition. Whether these fluid property changes are significant enough to mean a multicomponent mixture model is required is up to you.

 unischlaf August 25, 2011 03:09

Now I have the following settings:

1 domain for both meshes
in Fluid and Particle Definitions: Ideal Air Gas und CO2 Ideal Gas as Continuous Fluid
Turbulence model for both fluids is SST

At the nozzle inlet I have set the Bulk Mass Flow Rate and Volume Fraction of CO2 is 1 and of Ideal Air is 0.
At the pipe inlet I have set the Bulk Mass Flow Rate and Volume Fraction of CO2 is 0 and of Ideal Air is 1.

Is that ok?

 ghorrocks August 25, 2011 18:45

Sounds sensible.

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