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Gradual contractions in pipe

Gradual contractions in pipe

Gradual contractions in pipe

(OP)
Hello,

  I am looking at page A-26 in Crane's manual. It shows that for pipe with a gradual contraction with an angle of convergence of between 45 and 180, we are to use Formula 4.

Formula 4 is dependant on the sine of half the angle.

If I use an angle of 180 (abrupt change in diameter) then should this correlation not be equal to Equation 2-10 on page 2-11???

This does not make sense, since Formula 4 is divided by Beta ^ 4, there can't be legitimacy here?? They must equal if the wall angle = 180!!

Please explain this to me.

  Thank you.

 

RE: Gradual contractions in pipe

In my (1988) edition of Crane it seems you are referring to Formula 2 on Page A-26, and not Formula 4.

√(sin(180/2)) = √(sin(90)) = √1 = 1

Equation 2-10 gives the value for K1, which is based on the smaller pipe diameter.  Formula 2 gives the value for K2, which is based on the larger diameter.  K1 and K2 are related by  equations 2-5 and 2-11.

Katmar Software
Engineering & Risk Analysis Software
http://katmarsoftware.com

RE: Gradual contractions in pipe

(OP)
But it is divided by B^4?

Or is 1/B^4 just a factor that need not be considered when comparing the two equations?

Thanks katmar

RE: Gradual contractions in pipe

dbecker

Yes. Formula 2 is Equation 2-10 (Κ1) divided by Β4; that's what the second "=" is telling you.  
Yes. You need to consider the Β4 when comparing the two equations.  Κ1 ≠ Κ2.

As katmar stated, it's because Equation 2-10 is in terms of Κ1, while Formula 2 is in terms of Κ2. (Actually this applies to all the formulas on page A-26)

Patricia Lougheed

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RE: Gradual contractions in pipe

(OP)
Thanks for the clarification.

Makes sense now.

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