air blower capacity

[Don Jeansonne]

I am looking at building an air filtration unit from a used furnace blower. My question is how to determine the CFM capacity of a blower that I have. I figured that for my shop I need between 570 and 760 cfm for 6 to 8 changes per hour.
The blower I have is 1/10 hp 4.1 amp 1050 rpm and the wheel is 8.5" diameter and 5" wide. I found a Dayton blower listed at 1080 rpm, 8 5/8 dia, 5 1/4 wide, 3.66a with a 990 cfm in a catalog.

Can anyone help with some design tables or other type of engineering data?

[Paul Atkins]

I would think the efficiency of the 'wheel' would be more important than motor specs. A badly designed fan blade on the same motor as a good designed one would put out less air. In other words, It would have to be measured or have specs on the fan itself.

[Josiah Bartlett]

Another thing to consider is the surface area and air restriction of the filter media you are using- most squirrel cage blowers move a fair amount of air in the open, but once a filter is added efficiency drops off rapidly.

[Cliff Rohrabacher]

a filter?
You mean with a slide in type cartridge f ilter measuring somewhere arounf 1" by 24x24" or so?

Just build a box put a filter on the in flow and out flow and your squirrel in the middle of the stream and you'll be golden. Then hand that somewhere in the shop where it is both out of the way and in a good spot to get the air circulating is left on for long periods.

You could mess around with Delta P measurements & fan blade geometry, or you could just make the thing and put done to it. . Either way it will move air, and a squirrel cage fan will have a high delta P.

The reason for the high delta P is because of all the little vein blades that prevent much of the back flow against a pressure gradient. The more of them there are the more efficient the fan will be - up to some point.