Fully Developed Flow Past Orifice Plate: 20-40x Diam.

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Discussion Overview

The discussion revolves around the distance required for fluid to achieve fully developed flow past an orifice plate pressure meter, specifically addressing the commonly cited range of 20 to 40 times the diameter of the orifice. Participants explore standards and specifications related to this topic.

Discussion Character

  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant questions the validity of the 20 to 40 diameters figure, suggesting that a standard of 15 diameters of the pipe ID is more appropriate, depending on the beta ratio.
  • Another participant seeks clarification on the source of the 15 diameters standard and expresses interest in understanding the factors that contribute to this specification.
  • A participant provides links to ASME specifications that are relevant to the discussion, indicating that there are multiple sources for flow criteria, including variations from other organizations.

Areas of Agreement / Disagreement

Participants do not reach a consensus on the appropriate distance for fully developed flow, with differing views on the relevance of the 20 to 40 diameters figure versus the 15 diameters standard.

Contextual Notes

The discussion highlights the dependence on the beta ratio and the lack of clarity regarding specific tables or sources that define the standards mentioned.

Isoho
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Hi!

what is the distance that a fluid has to go to become fully developed flow past an orifice plate pressure meter?

I have read somewhere that it is 20 to 40 times the diameter of the constriction. Is this correct?
 
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The standard one has to follow for printed calculations to be valid is 15 diameters of the pipe ID, not the orifice diameter, downstream before any kind of disruption or change in flow path for. This does depend on beta ratio however. There is a table in the ASME specs that spells this out and gives the ranges required.
 
Thanks Fred!

I was wondering where you sourced that information from as I have just been on the ASME website and found a few papers relating to the matter but I was unable to find the table that you mention? (my beta number is 0.66). I would also really like to read up on the factors behind the 15D if you have any web links to how you know that.

Thank you for your help already though!
 

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