[Bldg-sim] IES CFD Modeling Issue: Reverse Flow through Diffusers

[JRR]

Hi;

The flow volume vs output pressure of the flow source is critical in 
these cases.  Are you modeling   1) Open bladed fans, 2) Tube axial fans, 
3) Centrifugal blowers ?? 

Have you tried using CBs in the reverse flow locations ???


The nearest application to your problem is the flow in turkey sheds. 
In the Mid Atlantic region they are typically 50 ft wide, 650 or 900 ft 
long and  7 ft to 9ft high
inside with blowers distributed along the side walls. 
In the Midwest they are 80 ft wide, and proportionately shorter.
These variations have been well examined by the poultry industry and  
Virginia  Tech University.
There is also the "Mid West Plan Service" which is run out of either the 
U of Minnesota or U Wisconsin.
It gives detailed information on large Agricultural buildings......

By the way if your room is 283 ft long and the ducts are 280 ft long,  
you already have a significant
problem......


Brain, Joshua wrote:

>Hello,
>
> 
>
>I am using IES to conduct a CFD model on a long and narrow room (283ft
>by 60ft) with three large ducts (square 4ft by 4ft) running along the
>ceiling (280ft long, 28ft off the floor). I have 18 diffusers equally
>spaced along each of the three 280ft ducts for a total of 54. Each
>diffuser has a CFM of 1110, an area of 3.75 sf, and a discharge velocity
>of 300 fpm. There is a single return grill at one end of the building. 
>
> 
>
>My problem is: when I look at the velocity vectors in the MicroFlo
>Viewer some of the diffusers have the air flowing backwards or into the
>diffuser, not flowing out as it is supposed to. This occurs across all
>three duct lengths at the same diffuser location. 
>
> 
>
>Has anyone else run into this and have they resolved the issue?  IES
>took my model and made changes to it only to find that they could not
>fix it. 
>
> 
>
>Thank you in advance for any advice, 
>
>Josh
>
> 
>
>Joshua Brain
>
>Mechanical Group 
>
>R.G. Vanderweil Engineers, LLP 
>
>274 Summer Street     Boston, MA  02210 
>
>Tel: (617) 423-7423 
>
>Fax: (617) 423-7401 
>
>Direct: (617) 956-4565 
>
> 
>
>www.vanderweil.com 
>
> 
>
> 
>
>
>  
>
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>
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