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how to test cfm

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March 20, 2002 6:15:43 PM

any one know of a good at home way to test how many cfm a fan puts out? i found an ac fan in some old equipment i junked, i think its a 120 mm, thing feels like it puts out a lot of air, and its very very quiet. i want to know if it really does put out a significant amount of air. i thought of getting a big trash bag that says how man cfm it is, but that probly would give scewed results when the weight of the bag starts pushing air back toward the fan.

i went to the tomshardware forums and all i got was this lousy signature.

More about : test cfm

March 20, 2002 8:52:11 PM

List the manufacturer, part numbers(P/N), and any other marking here and let us see if we can figure it out.

Other than that, you will probably have to go to a mechaical engineering lab or facility to figure it our.

<b>"Kenny! Give me the whoobie."

"You don't feed a baby chile!" - Mr. Mom</b> :lol: 
March 20, 2002 11:12:36 PM

Get yourself a <A HREF="http://www.torringtonresearch.com/fm100.htm" target="_new">Torrington FM-100 Flow Meter</A>. That should do for the most part. If you are looking into a fan that will break the 100CFM barrier, get the <A HREF="http://www.torringtonresearch.com/fm300.htm" target="_new">FM-300</A> model. It's a little bit bigger, but you will be the envy of all of your friends.

Seriously, if you know of anybody who has an anemometer (wind velocity meter), you can find out the velocity of the air moving through the fan, and then convert to CFM based on the area of the fan face. Don't remember that equation right now.

If you can get portable power hooked up to it (and have a little spare time and a lot of influence), you might be able to take it to an HVAC company, and they would definitely have all of the equipment you would possibly need.

VSP

<i>Whatever causes your water transportation vessel to maintain proper buoyancy.</i>
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March 21, 2002 3:18:08 PM

You need to know total air volume, the static pressure, and the velocity of the air.

See here for a diagram for <A HREF="http://www.users.dircon.co.uk/~nmb/fans/engineer/data/a..." target="_new">Static Air Pressure</A>.

<A HREF="http://www.airflow.com/glossary.html" target="_new">See here</A> for a set of difinitions and set of different tools to calculate velocity and maximum air volume.

Using the maximum volume and the velocity figures for a specific air pressure you could calculate the CFM. (Velocity of a specific volume of air.)

Or you could go find someone with the tools to calculate it and/or list the make and model of the fan here and have us look for the answer.

<b>"I put instant coffee in the microwave and almost went back in time" - Steven Wright</b> :lol: 
April 7, 2002 8:31:03 PM

well i found out what it is, i am happy :)  its a muffin 14 watt fan, spec sheet says 60-80 cfm. i have found it in online shops for 70 bucks! thats a pretty good find i would say.

i went to the tomshardware forums and all i got was this lousy signature.
!