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Maximum Centrifugal Fan Outlet Velocity

Maximum Centrifugal Fan Outlet Velocity

Maximum Centrifugal Fan Outlet Velocity

(OP)
Most specifications  inherited from grandfathers have an outlet velocity limitation of 10~12 m/s for centrifugal fans.Does anyone know what is the basis for this limit?Couldn't we  use a higher out velocity (say 16 m/s )for fan selection?This may result in a smaller fan.An expansion fitting can be used to connect the fan to duct work and bring down it down to duct  velocity(which could be around 10m/s).

Any thoughts???

RE: Maximum Centrifugal Fan Outlet Velocity

Noise and pressure drop are higher at higher velocity......

RE: Maximum Centrifugal Fan Outlet Velocity

as Willard3 indicated,... and also to get higher exit flow velocities you will need the fan to have higher RMP.  This would lead to a whole set of other considerations in the design.

RE: Maximum Centrifugal Fan Outlet Velocity

Centrifugal fan selected for optimum efficiency usually have a discharge velocity of around 8m/s or less.  The faster the discharge velocity, the smaller the fan (thus cheaper) but efficiency is reduced.  

Therefore need to confirm if efficiency or cost is of greater importance to the project.

RE: Maximum Centrifugal Fan Outlet Velocity

I have often been limited on my fan selections by speed as it keeps the noise levels down.  This surprised me the first time I was asked but it has come up on a fairly regular basis.

RE: Maximum Centrifugal Fan Outlet Velocity

"System effect" becomes very important if you use a discharge plenum, not much room for bad workmanship with high velocities.
Dynamic balancing of fans becomes even more important, a small wear of the fan shaft or small chip on a fan blade will result into a large imbalance and will create serious vibrations.

The slower, the better.

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