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Ventilation to reduce the CO2 concentration

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Old   March 29, 2012, 10:17
Default Ventilation to reduce the CO2 concentration
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I'm simulating the air flow inside a room to investigate the effectiveness of ventilation in reducing the CO2 concentration in the room.

The domain is a simple room with ventilation inlets and ventilation outlets.

The human breathing ( Inhalation of O2 and Exhalation of CO2 ) has to be modled in the room.

I considered 3 such human sources of CO2 in the room.

From a biomechanics journal I found the graphical data for the breathing cycle in humans.

The journal reports the cycle for a time of 4 [s] .

However I feel that if my purpose is just to see the effectiveness of ventilation in the room then a time of 4 [s] is too short.

so I'd like to see a more realistic situation by allowing the ventilation to occur for about 10 minutes.

Also I feel that it would be apt in this case to select the maximum flow rate for breathing from the graph ( breathing cycle )

And use it to model the human sources instead of simulating the entire cycle itself.

Since the purpose is only to investigate the effectiveness of ventilation in terms of reducing the CO2 concentration in the room.

Could some one please comment on this approach.
Best regards,
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Old   March 29, 2012, 23:46
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Glenn Horrocks
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Your thinking is correct. If your model is a slow time scale then you (hopefully!) can compress the complex short time scales into a time-averaged effect for a long time scale simulation.

I will leave it up to you to determine if the velocity of a person's breath is signfiicant, in your case I doubt it but I do not know the details of what you are doing. In that case then a fairly simple approach which uses a sink on the O2 concentration and a source on CO2 should feasible, with the rate matched to the time-averaged rate.
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