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Pressure Drop over a Rectangular Opening

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nuuvox000

Mechanical
Joined
Sep 17, 2019
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344
Location
US
Can anyone point me to something that explains how to find the pressure drop of a rectangular opening in a wall for a certain CFM?
Thank you.
 
SMACNA and ASHRAE show the C-values. They differ for air entering, or exiting.

Also some here
 
Thanks, couldn't find much in ASHRAE but SMACNA had a lot of C-values. Nothing for a wall openings but I chose the closest I could get from their duct coefficients.
 
In most cases it flows from a duct to a room. but it also makes a difference if the duct discharge is in the same plane with the wall, or if the duct sticks out.
If you find multiple values, use the most conservative value.
 
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