Maximum centrifugal fan outlet velocity

[abbasi]

Well having to work on so many centrifugal fans such as NICOTRA, KRUGER, LAU, YILIDA etc. I still wonder what is limit associated with fan outlet velocity?
Some say it is 1800-2800 FPM based on application. I have attached a table that shows some recomendations.
Can anyone narrate where AMCA(AIR MOVEMENT CONTROL AUTHORITY)has drawn a line? My problem is that few companies select fans on 2000 FPM outlet velocity and less and others go higher to 3000 FPM outlet fan velocity for same equipment.
What should be ideal/allowable maximum fan velocity and fan efficiency?
A detailed reply will be worthwhile

[abbasi]

Please folks come on!!! reply

[Abby Normal]

the limit on the outlet velocity is baesed on the limit of what the fan wheel is allowed to move

The outlet is more or less fixed.

There are low pressure, medium pressure and high pressure duct systems.

A fan in a medium pressure system can easily have an outlet velocity of 2000 fpm or higher

There are system effects on these fans, particularily if conditions are less than ideal right at the fan discharge, and these losses get quite substantial when the velocity is high as they are proportional to velocity squared.

Example on a forward curved fan you can have a non-ducted loss when it blows air through a heat exchanger or a coil. The non ducted loss is about 1.25 times the velocity pressure.

Assuming standard air, the velocity pressure at 2500 FPM is about 0.39 " wc or 97 pascals, and the associated loss would be 121 pascals or about 0.49 inches.

If a larger fan was used and the outlet was say 1500 fpm, then the velocity head is only 0.14 " WC

[Abby Normal]

backward incline air foil fans tend to have a lower system effect on the discharge and the non ducted loss on these fans may be somewhere around 0.65 times the velocity pressure.

So beside the type of duct system, it has to do with the type of fan wheel

[Brian_UK]

:off topic:
Please folks come on!!! reply:mad: Will you please learn to be more patient.
Just because you want answers does not mean that everyone in the world has to rush to your assistance. :mad:

[Abby Normal]

yah, some people are 12 to 13 hours time difference with respect to the Op

[abbasi]

:off topic::mad: Will you please learn to be more patient.
Just because you want answers does not mean that everyone in the world has to rush to your assistance. :mad:

Ok
Now ma question stands where has AMCA drawn a line, i know losses are more in high outlet velocity but if i select my AHU what fan outlet velocity is recomended and what is maximum (outlet velocity)i can use?
i mean sometimes we are priced out in our AHU coz other companies select smaller dia fan with high outlet velocity upto 3000 FPM and we work in region of 2000 FPM:confused: