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Line Sizing: Pressure Drop/ Minor Losses Coefficient Of Valves, Fittin

pressure drop line sizing resistance coefficient minor losses valves & fittings resistance minor losses table minor losses calculations

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#1 zavtranguyen

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Posted 10 May 2021 - 09:43 PM

Hi every one, in "line sizing" when we caclulate the item "pressure drop", for such minor losses as of valves and fittings, resistance coefficients k should be taken from tables. Howerver, i see that we can also use formula to get those k and i have some formulas for this purpose, but i cann't check the rightness of those formulas, or any one could help me to confirm from which handbooks/documents the formulas were taken.

 

Please find the formulas below

 

Valves and fittings (PNS = pipe norminal size, inch)

Formula

1. Pipe entrance

k= 0.5

2. Pipe exit

k= 1

3. Elbow 90

  • Re<500000:

k =0.00476*(ln(Re))^2-  0.1574*ln(Re)*1.446+(Re/500000)^0.25*(0.01163*(ln(e/D))^2+0.2278*ln(e/D)+1.1055)

  • Re>=500000:

K = 0.01163*(ln(e/D))^2+0.2278*ln(e/D)+1.3055)

 

4. Tee turn

k=1

5. Globe v

  • PNS > 26”: k=4
  • PNS<=26”: k= 10^(-0.2258*log(PNS)+0.9)

 

6. GATE V

 

  • PNS > 26”: k = 0.1
  • 5”< PNS <=26”: k = 10^(-0.1542*log(PNS)-0.7782)
  • PNS < 5”: k = 10^(-0.2382*log(PNS)-0.7195)

 

7. CHECK V

 

  • PNS >= 20”: k = 0.6
  • 2” <PNS < 20: k = 10^(-0.1856*log(PNS)+0.01967)
  • PNS <2”: 10^(-0.2534*log(PNS)+0.3551)

8.. BUTT V

 

  • PNS> 22”: k= 0.3
  • 6”<PNS<= 22”: k= 10^(-0.6523*log(PNS)+0.3527)
  • PNS<= 6”: k= 10^(-0.2287*log(PNS)+0.02307)

9. BALL V

k=1.5

 

 

Thanks a lot.


Edited by zavtranguyen, 10 May 2021 - 10:00 PM.


#2 breizh

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Posted 10 May 2021 - 10:52 PM

Hi,

Consider the link attached https://neutrium.net...-head-k-method/

together with the paper from Hooper .

 

Use the link above to learn about 2K and 3K methods. , Get a copy of Crane Flow of fluids through valves, fittings and pipe TP N 410

 

Good luck

Breizh 



#3 zavtranguyen

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Posted 11 May 2021 - 08:33 PM

Thank you for your valuable information, Mr.Breizh.



#4 latexman

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Posted 11 May 2021 - 08:53 PM

For:
“9. BALL V
k=1.5”

I think k = 0.1 for full port and k = 0.2-0.5 for reduced port. k = 1.5 for ball valve is too large.

#5 zavtranguyen

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Posted 12 May 2021 - 12:31 AM

Thank you Mr.Latexman, it's really too large for ball valve, so i have some doubts that whether these formulas are corret or not.



#6 iOM

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Posted 19 August 2021 - 03:29 PM

I've been reading the crane TP 410 for while, the only difficulty that i'm encountering is that the angle specified in the applicable condition for each fitting/valve equation. I have bought a book which specified the angle for a reducer as alpha = 2*atan((D2-D1)/1.2*L) and i have seen another reference which provides the following formula to get the reducer convergence angle alpha = atan((D2-D1)2L)), and i'm not sure which to use honestly. I got all the dimensions for reducers from ASME standard. 

 

How can someone calculate the right angle for the reducer/expander as well as the reduced bore valves as per Crane TP410? 

 

i'd appreciate your insights on this, thanks



#7 breizh

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Posted 19 August 2021 - 07:08 PM

Hi ,

Consider this extract from "piping a practical and comprehensive guide " by Rennels and Hudson .

Simple trigonometry problem  :

tan(alpha/2)= (R1-R2)/l = [(D1-D2)/2] /l 

alpha =2* atan {( D1-D2) /(2*l)}

 

For Ki calculation consider the link underneath:

https://cheguide.com...ng_fitting.html

 

Note : The Chemical engineering fluid mechanics  (2nd edition) By Ron Darby is confusing , missing to stipulate in writing the case teta is  above 45 , corresponding to the 2nd sets of equations for contraction.  

 

good luck 

Breizh



#8 katmar

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Posted 23 August 2021 - 01:43 PM

@Zavtranguyen - when you quote complicated formulas like you have done above it is always best to give the references from where you obtained them. Random formulas taken off the internet are dangerous.

 

@iOM - you should not get too hung up on these formulas. It has always amused me that every fluids text gives some version of these elaborate formulas, but they have no relevance to practical piping calculations.  Nobody fabricates a reducer like that except in very specialized instances.  In >99% of cases we just buy an off-the-shelf pipe reducer.  Hooper is one of the very few authors who recognizes this fact and gives appropriate advice.



#9 iOM

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Posted 31 August 2021 - 01:06 PM

Thanks a lot Breizh and Katmar, I have already got my copy of the "piping a practical and comprehensive guide" and it really explains what happen exactly in the piping components.

 

thnx again.






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