Air flow relative to duct size

[amd]

How much air can a 8 x 5 1/2" rectangular duct flow?

[second opinion]

It would depend on the velocity and the friction rate that you chose. if you where using around 600 fpm around 160 cfm

[genduct]

You have been a long time user. Use my profile and I'll be happy to share some simple thoughts that may help
Mike

[hvacvegas]

How much air can a 8 x 5 1/2" rectangular duct flow?

It would depend, as said, on friction rate, and velocity.

for your general run of the mill guess, I'd agree somewhere in the 160 range.

But, as an example:

10 round caries (general rule) what, 300-400 cfm?
I've got a system I'm doing where I'm moving 2k cfm through 10", for a special exhaust, and thats design from the manufacturer.

as a general rule, but does not cover all situations and varies system by system:
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