Air intake duct design
Air intake duct design
(OP)
I work at a hospital and we're having an air intake duct of 24"x16" with an approx. length of 125' and 3 elbows which will need to handle 48,500 CFM ( 3 different air handlers) and I think it's undersized. Any help?
Thanks
Thanks





RE: Air intake duct design
RE: Air intake duct design
RE: Air intake duct design
Just a comment on BronYrAur's post, 500 fpm is a good rule of thumb for louvre sizing, but I generally recommend that you review the louvre manufacturer's sizing charts. They will list a point of 'rain penetration' on their charts which can vary significantly depending on louvre design.
RE: Air intake duct design
It may be that your total AHU has the 48500 cfm, the OA flow at about 10 -15% of that amount (old rules of thumb) would make the OA cfm at about 4000-6000 cfm. Even with this senario, the 24X16" is too small. I believe 1000 fpm is max velocity I would bring air in. This will be about 2400 cfm outside air.
Going back to your question: yes the duct seems to be bery undersized no matter which way we look at it.