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nhahn
Posts: 92
Registered: ‎01-18-2006

appropriate inlet/outlet BCs for building ventilation?

138 Views, 1 Replies
08-12-2013 12:38 PM

I'm curious what boundary conditions other users have found useful for a building ventilation application?  I'm modeling a single room with an exhaust fan.  It's drawing through a closed door and blowing through a vent to outdoors.

 

It doesn't seem appropriate to put zero pressure BCs on both inlet and outlet, but I can't really think what else would be appropriate.  Also, it doesn't seem like modeling the small gaps around the door is ideal.  Suggestions (especially based on successful models or standard practices) would be helpful.

 

I'm using a fan curve for the fan itself.

 

Thanks.

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wildej
Posts: 840
Registered: ‎08-25-2011

Re: appropriate inlet/outlet BCs for building ventilation?

09-03-2013 08:45 AM in reply to: nhahn

Hi,

 

P=0 should be OK, unless you know what the pressure happens to be up or downstream?

Modelling gaps around doors is not ideal for analysis speed but it can sometimes be necessary. If really required, ensure you have a good quality mesh though here - use the Gap Refinement and within Advanced Meshing, set the Gap Elements to 3. This should automatically capture a good mesh for you.

 

The alternative would be to set the door as a resistance with a minimal free area ratio, then you would at least capture a pressure drop through the system. It depends on the focus of the analysis really.

 

Hope that helps.

 

Kind regards,
Jon



Jon Wilde
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