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Participant

Join Date: Jan 2012
Posts: 2

Centrifugal Blower CFM: How To Calculate

01/25/2012 12:24 PM

Blower fan Dia 600mm,

Blower fan wigth 80mm ,

Blower fan suction area 210mm,

Blower fan number of blade 12 nos,

Blower outer cover 117mm wigdh,

Blower outer cover dia 810mm,

Blower outer cover suction area 210mm,

Blower air out area 177x177x177x177mm

Power 15hp , 2880 RPM

How much for out air cfm , pls sombody help me and how to calculate formula

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Guru

Join Date: Oct 2008
Posts: 40709
#1

Re: centrifugal blower cfm how to calculate

01/25/2012 12:27 PM

Or, is this homework?

And don't you think that the shape/angle/form of the blades might be improtant, too?????

As a last resort:

Participant

Join Date: Jan 2012
Posts: 2
#3

Re: centrifugal blower cfm how to calculate

01/25/2012 12:37 PM

fan degree 35 , fan shape flat and straight , i am a manufacturer for textile machines , i was buy fan from one small company but this is custamised design they dont no perfect calculation , digital meter to buy but i want to improve nolage to manualy thats why i am asking calculation formula if you know pls tell me

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Join Date: Mar 2007
Location: Rosedale, Maryland USA
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#6

Re: centrifugal blower cfm how to calculate

01/26/2012 8:21 AM

There is no ideal formula to give exact CFM for a blower. There are too many variables that fall into place in the mechanical construction to deal with. Example is you give the pitch at 35 degrees. So if the impeller has the blades welded on each blade may not be exactly 35 degrees. Close but not exact, so each impeller would preform a little different. Another is the clearances. You have to allow for some tolerances in fabrication. That is why company did was not able to give an exact CFM output. Also the name plate rpm on the motor. It is only a rating maybe different in application. The only way is to test it. They do test them just not every one this gives them an idea what their average losses are. Which they can then figure into a formula.

If you want a general formula of ideally what the the blower CFM should be volume of the housing times RPM of the motor.

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#2

Re: centrifugal blower cfm how to calculate

01/25/2012 12:34 PM
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#4

Re: centrifugal blower cfm how to calculate

01/25/2012 1:03 PM

You can estimate cfm by using hp...

 HP = Volume (cfm) x Pressure (lb. Per sq. in.) 229 x Mechanical Efficiency of Fan

For purpose of estimating, the eff. of a fan or blower may be assumed to be 0.65.

 Note: Air Capacity (cfm) varies directly with fan speed. Developed Pressure varies with square of fan speed. Hp varies with cube of fan speed.
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#5

Re: Centrifugal Blower CFM: How To Calculate

01/25/2012 2:36 PM

I like the one-dimensional suction port and the 4-dimensional discharge!

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Associate

Join Date: Feb 2012
Posts: 37
#7

Re: Centrifugal Blower CFM: How To Calculate

02/21/2012 12:16 AM

Centrifugal Fans and Blowers typically have one of seven types of wheels that draw the air into the inlet of the blower housing, through the wheel, and discharges it at 90 degrees out through the discharge of the housing.

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