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28-11-2008, 07:15 AM #1
Maximum centrifugal fan outlet velocity
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
Our nose is our personal air-conditioning system: it warms cold air, cools hot air and filters impurities
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28-11-2008, 11:09 AM #2
Re: Maximum centrifugal fan outlet velocity
Please folks come on!!! reply
Our nose is our personal air-conditioning system: it warms cold air, cools hot air and filters impurities
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28-11-2008, 11:44 AM #3
Re: Maximum centrifugal fan outlet velocity
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 " WCLast edited by Abby Normal; 28-11-2008 at 11:48 AM.
Take the V out of HVAC and you are left with a HAC job
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28-11-2008, 11:51 AM #4
Re: Maximum centrifugal fan outlet velocity
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 wheelTake the V out of HVAC and you are left with a HAC job
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28-11-2008, 08:01 PM #5
Re: Maximum centrifugal fan outlet velocity
Last edited by Brian_UK; 28-11-2008 at 11:52 PM.
Brian - Newton Abbot, Devon, UK
Retired March 2015
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28-11-2008, 11:41 PM #6
Re: Maximum centrifugal fan outlet velocity
yah, some people are 12 to 13 hours time difference with respect to the Op
Take the V out of HVAC and you are left with a HAC job
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29-11-2008, 06:04 AM #7
Re: Maximum centrifugal fan outlet velocity
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 FPMOur nose is our personal air-conditioning system: it warms cold air, cools hot air and filters impurities
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