FRICTION LOSSES IN PIPE FITTINGS 1

[kunletee]

Please, i want to find out the values for frictional loss coefficient (k) to be used for the following components of a pipeline system:
1.flowmeter
2. Deaerator
3. 3 way valve
Is there a general formulae for frictional loss coefficient (k) for a reducer or expander?
Thank you.

kunletee

 

[dcasto]

Crane TP410 and GPSA handbook. Something like
K = (.8 * sin(Omega/2)*(1-beta^2))/Beta^4 if Omega <45Deg
K = (.5*(1-Beta^2) * (sin (Omega/2))^.5)/Beta^4 if $% <Omega < 180 degrees

 

[Ashereng]

It would also depend on the type of instruments.

There are lots of flow meters, from orifice plate (lots of pressure loss) to clamp on ultrasonic (very little pressure loss).

Similarly, for a valve. It would depend on your valve.

For reducers, I would think that there are tables or formulas (I will leave that to my piping brethrens).

For deaerators, not a clue. Sorry.

"Do not worry about your problems with mathematics, I assure you mine are far greater."
Albert Einstein
Have you read FAQ731-376 to make the best use of Eng-Tips Forums?

 

[katmar]

1. Flowmeter
I agree with Ashereng on this one. There is such a wide variety of flowmeters available that it is impossible to answer this meaningfully. Ask your supplier for data applicable to your specific meter.

2. Deaerator
I doubt very much whether a deaerator would follow the behavior modeled by a single K value. The pressure drop through the deaerator will be made up of several different components, and it would be best to get relevant data from the supplier for this as well.

3. 3-Way valve
You will find data in the open literature for valves, and this is generally good enough for piping design purposes. 3-Way valves are fairly special items and could vary from supplier to supplier. For fully developed turbulent flow in a 4" plug valve I would use a K of 0.5 for straight through flow, and 1.5 for flow through the branch.

4. Reducers
This has always puzzled me. Every fluids book you read (including Crane #410) has plenty of data and correlations for conical tapered reducers, but when you go into any plant where there is typical piping you will find that this style of reducer is extremely rare. >99% of installed reducers are of the standard profiled variety, but you will struggle to find data on these. The only data I have seen comes from nearly 20 years ago in a paper by William Hooper (the two-K man). It was published in Chemical Engineering, Nov 7, 1988 pages 89-92. Even Hooper said of his correlation "it looks reasonable, but no published data are available for checking its accuracy".

Hoopers correlation when used in the large-to-small orientation is
K = [ 0.1 + 50/Re₁ ] x [ (D₁/D₂)⁴ - 1 ]
where Re₁ is based on the larger (i.e. inlet) diameter. D₁ and D₂ apply to the inlet and outlet respectively.

In the small-to-large orientation a profiled reducer is much less efficient and Hooper regards it as a sudden expansion. For turbulent conditions the correlation is
K = [ 1.0 + 0.8 x f₁ ] x { [ 1 - (D₁/D₂)² ]² }
where f₁ is the Moody friction factor based on the smaller (i.e. inlet) diameter.

Both these K values must be applied to the velocity at the inlet to the reducer.




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