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Thread: Rectangle Belmouth Max ft/min?

  1. #1
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    Question Rectangle Belmouth Max ft/min?

    Hey all, first post so I apologize if posted in the wrong group.

    Working on a project that has an exhaust fan flow rate 66,000 cfm. The job requires a “rectangular bellmouth”. The fan outlet size is 57.63" x 43". I ran a quick calculation to see its velocity is 4108 ft/min. Im trying to size the bellmouth but I am unfamiliar with such high velocity. What is the maximum velocity we should go? The fan is in the middle of a field and no building around it.

    If the belmouth transitions to 55"w/40"d/48"h the velocity would then be around 4632 ft/min. is that sufficient?

  2. #2
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    No help here. But what is the purpose of this fan setup?

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  4. #3
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    I would contact the manufacturer for Insite.

    If they require it to meet performance ratings, they should be able to tell you a bit more about how aggressive or not the transition needs to be.


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  6. #4
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    Sounds like homework.
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  7. #5
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    Let me ask this of you all. I have barely head of the bellmouth fitting/piece/transition thing. So, is there such a thing are a rectangle bellmouth fitting? A bell is rounded curved kinda. Just curious!

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  9. #6
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    Poodle Head Mikey is offline Membership Chair/ARP Committee / Professional Member*
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    What are the specifics of the application?

    PHM
    ------


    Quote Originally Posted by Makakilo View Post
    Hey all, first post so I apologize if posted in the wrong group.

    Working on a project that has an exhaust fan flow rate 66,000 cfm. The job requires a “rectangular bellmouth”. The fan outlet size is 57.63" x 43". I ran a quick calculation to see its velocity is 4108 ft/min. Im trying to size the bellmouth but I am unfamiliar with such high velocity. What is the maximum velocity we should go? The fan is in the middle of a field and no building around it.

    If the belmouth transitions to 55"w/40"d/48"h the velocity would then be around 4632 ft/min. is that sufficient?
    PHM
    --------
    The conventional view serves to protect us from the painful job of Thinking

  10. #7
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    Thread Starter
    Quote Originally Posted by TechmanTerry View Post
    No help here. But what is the purpose of this fan setup?
    Sorry for the delayed response. Busy month. It is exhaust setup for an underground facility.

  11. #8
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    We decided the discharge size was sized that we wont be using a bellmouth. Sorry for the delayed response.

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