As the back-pressure increases downstream from the blower, the flow rate drops significantly. It drops even more if the flow is significantly restricted on the inlet side. (You need to be careful about that.)

Typically, 'blowers' are designed to give maximum flow against a certain amount of back pressure, as when air is being delivered through a long or relatively narrow pipe. 'Fans' are designed to deliver a greater flow but only at low pressure. They can be 'radial' like an aircraft propeller or axial with the shaft at right angles to the flow.

They normally have specifications which include performance curves where flow rate is plotted against back pressure. This is the data you need to file away when you find one that performs well under test with the exact setup you are using. I really think you have to experiment.

I suggest you contact a supplier of fans for ducted air-conditioning installations, and ask if you can borrow a couple to try before you buy.

Ian Russell
www.interactives.uk

------Original Message------
From: Erich Rose
Sender: Informal Science Education Network
To: [log in to unmask]
ReplyTo: Informal Science Education Network
Subject: Blower Fans
Sent: 28 May 2009 16:17

ISEN-ASTC-L is a service of the Association of Science-Technology Centers
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For an "air play table" or a Bernoulli blower what would you suggest as a minimum air flow? CFM? I have used different fans in the past with different results. More often than not they were used squirrel cage fans that we had laying around and had a wide variety of outputs.  What I am looking for is some feedback from others about what they found worked best.

--
Erich Rose
Exhibit, Environmental and Industrial Design
807 The Living End
Austin, TX 78746
512-626-9930; [log in to unmask]

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