selecting an exhaust fan for a straight duct 1

[kunkol1]

Hello,

I need to select an exhaust fan to extract nitrogen vapour at 77K(-196C) from an enclosed machine of size 1m x 1m x 1.5m through a duct (about 2m long)to the atmosphere. Can anyone explain the calculations i have to do to select the appropriate fan?

I look forward to hearing from you.
Thanks.

 

[willard3]

This is not a simple problem as the gas is not standard nor is the temperature standard nor, I guess, will the duct material be standard.

 

[kunkol1]

Yes, that is right. The duct material could however be standard and insulated if there are safety issues. Do you know the calculation required so that a standard rated fan can be chosen to work under these conditions?
Thanks

 

[Drazen]

-196 degrees C? Certainly not.

Where would you exhaust that vapor, which apparently presents health hazard? You should have extremely good mixing with outside air at short distance from exhaust point, means some large effective velocities at the outlet.

I believe you should find very special fan if such exists at all.

 

[kunkol1]

The vapour would be exhausted to outside air. The plan is to extract the nitrogen vapour produced in the machine in about 20minutes. so i don't think there would be a need for large velocities at the outlet

 

[MintJulep]

I think you should consider using an ejector rather than a fan.

You'll have a very difficult time finding a fan with bearings and lubricant that can cope with your temperatures.

You could power the ejector with a conventional fan or blower.

This would also give you some dilution of the exhaust.

 

[willard3]

Ahhhhh..... the trusty venturi.

 

[Compositepro]

I don't see any reason that a standard squirrel cage blower would not work fine for your application.

 

[RossABQ]

Is this to exhaust an environmental testing chamber supplied with liquid nitrogen?

 

[berkshire]

kunkol


kunkol is Offline:
Posts: 1 Designing/selecting an exhaust fan

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Hi all,
I'm a mechanical engineering student working on a group project which involves designing a machine which uses liquified nitrogen during its operation. I want to design an exhaust fan-duct system to extract the the nitrogen vapour to an open environment. I don't know how to go about selecting an appropriate fan or calculations required to ensure the system is efficient; so any help will be appreciated. Thank you.

Kunkol
Did you read the remarks about student posting in this forum?
B.E.

 

[RossABQ]

Well isn't that special?!