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Anonymous Poster

Modulation of a Fan

06/28/2010 4:40 AM

our gas collection and treatment system is equiped with a centrifugal fan. when the system resistance is reduced, the flow rate reduces instead of increasing. we want the flow rate to be constant independent of the system load.

also, when the system load decreases, the quantity of available gas decreases

what do i do to modulate the fan inorder to have constant flow rate at all times
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Tornado
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#1

Re: modulation of a fan

06/28/2010 4:57 AM

Actually measure the flow rate by pitot tube or something. Interface this signal with a VFD to drive the fan, together with some programming, to maintain a (nearly) constant flow.

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Kaisan
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Join Date: Nov 2009
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#2

Re: modulation of a fan

06/28/2010 5:51 AM

When the system resistance is reduced a centrifugal fan will supply more flow not less (up to a "stonewall" point where it will not increase further). A reduction in flow rate with a reduction in system resistance is against the laws of physics. You have some other phenomenon coming into play such as belt slip or something else.

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