FRICTION LOSSES IN PIPE FITTINGS
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?
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.
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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