air flow manifold and branch ducts

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jehemer
Posts: 1
Joined: Sat Mar 03, 2012 4:42 pm

air flow manifold and branch ducts

Post by jehemer »

I have a system which has a main manifold and 8 branch ducts.
The manifold is 150 ft in length rigid duct.
Air supply is at the center of the manifold.
Each of the 8 branch ducts is to supply 100 cfm discharged to atm.
Each branch length is 50 ft in length flexible duct.

How is the sizing on this system to be calculated.
admin
Site Admin
Posts: 375
Joined: Mon Feb 08, 2010 7:47 pm

Re: air flow manifold and branch ducts

Post by admin »

This kind of problems should be treated and solve like pipe network problem.
Are branches placed on some equal distances between each other and connected to main pipe? If the main pipe is 150 ft and there are 8 of branches, is distance between each other 150/8?
Anyway, the pressure on the exit of each branch is atmospheric and pressure in the center where the air is supplied should be known. To have equal cfm in each branch, its diameter should be calculated as you said flow rate should be 100 cfm. With known pressure difference you can calculate pipe diameter of each branch.
Pressure drop from manifold center to branch connection can also be calculated based on the total flow rate of all branches that are connected up to that point.
I hope that this helps to start, but some picture with distances and eventual pipe diameters would be help.
Pipe flow calculations - since 2000
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