Engineering Calculating CFM for Inline Fan - 420 CFM Minimum

[markmess]

Homework Statement

I have no idea about this I am sorry to say but I don't know where to turn.
I was wondering if there is a formula to figure how much of a fan CFM is needed if I am running 80 feet of 3" PVC with 7 openings at the ends

Relevant Equations

I also need to know what happens when a inline fan that has (let's say) 600 CFM but it is made for a 10" duct connection and you reduce it down ( at the unit) to 3" in and 3" out? Or is there any difference if it is reduced to 3" in and I keep the 10" out?

I was told if I need 60 CFM at each opening multiply the mount of openings by the 60 and that would be the minimum of CFM inline fan I need. so 7 x 60 420 CFM but I need to figure if I reduce the pipe at the fan and how many feet it is running , if that has an effect?

 

[Lnewqban]

Welcome, Mark!

Any fan is defined by two main things: how much volume of air it moves (CFM stands for cubic feet per minute) and how much static pressure it can generate inside a duct (inches of column of water in a U manometer).
Each fan follows a curve of performance, which is a series of points that define volume and pressure.

A long duct with many turns imposes certain amount of resistance to the flow of air (you need pressure to overcome that resistance).
For that combination, only certain volume of air will be delivered by that fan.

Please, see:
https://greenheck-cms-prod.azureedg...n-articles/perf_basics.pdf?sfvrsn=6df9b7ac_13

https://content.greenheck.com/public/DAMProd/Original/10002/FanFundamentals.pdf

https://www.grainger.com/know-how/e...per fan selection. ... 4 Sound Levels (Sones)