What is the most efficient & reliable flow (air) measurement procedure in a rectangular duct?

What is the most efficient & reliable flow (air) measurement procedure in a rectangular duct?

  • Hi Suvadeep,

    What is the size of the rectangular duct?
    And is the air clean or with moisture, solids (ash), gas emissions?

    Kind regards,
    Travis
  • In reply to Travis Stone:

    Hi Travis,

    Thanks for the response.

    Please note fluid is clean air & duct size is 1200mmX800mm.

    Kind regards,
    Suvadeep
  • In reply to Suvadeep:

    Hi Suvadeep,

    The Rosemount Annubar(TM) averaging pitot tube will provide a reliable and accurate measurement, with easy installation in a rectangular duct: www.emerson.com/.../rosemount-485-annubar-primary-element

    Sizing for this installation can be done with Toolkit, which is a free download if you do not already have it: www.emerson.com/.../about-sizing-and-selection-tools

    Best Regards,
    Dan
  • In reply to Dan Cychosz:

    Hi Dan,

    Thanks for the guidance and supportive links.

    My last and final clarification regarding upstream and downstream recommended straight length. As per Reference Manual
    00809-0100-4809-Table 2-2 upstream and downstream dimensions are indicated as some numerical values for different type elbow orientation. Please clarify me whether numbers are the multiplier of pipe dia for maintaining desired straight lengths?

    How it can be related to rectangular duct and what is recommended upstream and downstream straight length for 1200mmX800mm?

    Kind regards,
    Suvadeep
  • In reply to Suvadeep:

    You are correct in that the values referenced are a multiplier of pipe diameters. For duct installations we always recommended a site review or drawing review by a local Rosemount representative since ducts can have more challenging flow disturbances than pipes which might include internal bracing, heat exchangers, straightening vanes, filters or other equipment.

    If the duct is free of these disturbances, you can generally follow the recommendations in the reference manual. We always recommend mounting the Annubar flow meter across the widest part of the duct, and this should be used for you straight run calculation as well. For a single elbow (out of plane), we recommend 10 diameters (or 12 m) upstream and 4 diameters (4.8 m) downstream.

    If you have pictures or drawings available to review for this application, I'd be happy to take a look at it in more detail for you. I can be reached directly at dan.cychosz@emerson.com.

    Thank you,
    Dan
  • In reply to Dan Cychosz:

    Special thanks to Mr. Dan for the input.

    However, practically on straight length is available for the case I am talking about. Hence other than Annubar, any other alternate solution if available, kindly inform with details.

    Thanks & Regards,
    Suvadeep Sarkar