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Old   June 5, 2011, 08:18
Default CO2 concentration simulation
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William Shaw
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Hi everyone, I'd like to simulate the CO2 concentration using CFX for a HVAC system, but I cannot figure out how to define CO2 in CFX-pre. Is there CO2 listed in CFX material library? How to simulate the CO2 concentration in a room with air?
Thanks!


PS: does anyone know how to use Macro Comfort factors?
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Old   June 5, 2011, 18:55
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Glenn Horrocks
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There are simple approaches and complex approaches.

The simple approach is to model the CO2 as an additional variable. In this case you just put a marker in the gas which convects and diffuses with the gas. If the CO2 does not affect the properties of the gas this is a good approach and is very simple to apply.

The complex approach is to use a multi-component fluid, so you model the composition of the gas. This can handle the properties changes as the CO2 concentration changes. It can also handle chemical reactions and other advanced stuff. Only do this approach if the CO2 changes the properties of the gas or if you have chemistry in there as well.
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Old   June 10, 2011, 08:30
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William Shaw
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Quote:
Originally Posted by ghorrocks View Post
There are simple approaches and complex approaches.

The simple approach is to model the CO2 as an additional variable. In this case you just put a marker in the gas which convects and diffuses with the gas. If the CO2 does not affect the properties of the gas this is a good approach and is very simple to apply.

The complex approach is to use a multi-component fluid, so you model the composition of the gas. This can handle the properties changes as the CO2 concentration changes. It can also handle chemical reactions and other advanced stuff. Only do this approach if the CO2 changes the properties of the gas or if you have chemistry in there as well.
how could i put a marker in the gas? thx!
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Old   June 11, 2011, 07:29
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With an additional variable, set to diffusion/convection.
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Old   June 16, 2011, 09:12
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William Shaw
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With an additional variable, set to diffusion/convection.
I cannot find how to set to diffusion/convection
You mean set the Option of Addition Variable to Diffusive Transport Equation or Transport Equation?
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Old   June 16, 2011, 18:57
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Diffusive transport equation is the one.
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