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Inlet velocities for Centrifugal Fans

Inlet velocities for Centrifugal Fans

Inlet velocities for Centrifugal Fans

(OP)
What is a reasonable range for inlet velocities for the inlet of a centrifugal fan.  My discharge velocity is about 2,850 fpm at 1" W.C. static pressure.  Is an inlet velocity of over 4200 ft/min excessive?

RE: Inlet velocities for Centrifugal Fans

At these higher inlet velocities, prerotation and fan effects will increase pressure losses. Noise will also be a problem.
  
Check AMCA and ASHRAE for fan inlet conditions.

RE: Inlet velocities for Centrifugal Fans

mwpeters49,

Acceptable inlet velosity depends on density (temperature) of medium. What is application of the fan? Can you give more details of medium (temperature, density) and fan (inlet/outlet size, class, motor HP)?

regards,
curtis

RE: Inlet velocities for Centrifugal Fans

(OP)
Curtis,
This is for a HVAC application, specifically for a Industrial Evaporative Cooler.  Discharge pressures are low, about 1" w.c. static or less and using a size 36 I figure we need a 7.5 hp motor. The medium is air and we will be at STP, 0.067 lb/ft^3 at 70 F.

RE: Inlet velocities for Centrifugal Fans

4,200 ft/min seams high. Usually if there is no other specific requirement I would keep it around 2,000 ft/min for air at 70 F.
Regards,
curtis

RE: Inlet velocities for Centrifugal Fans

If you're talking about the inlet bellmouth of a fan, up to 15K fpm at this location is not at all unreasonable.

It's an easy issue to resolve - check out the mfr. flow design vs. open inlet area of the fan provided...
 

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