Christopher Wright wrote:
> On Feb 22, 2008, at 5:12 PM, kiqbal9@yahoo.com wrote:
>
>> I am not aware of any paper in this regard. Basically, the straight
>> length is require to get guaranteed laminar flow before flow
>> element in which all flow equations give required and predictable
>> results and hence flow element accuracy.
> To quibble a little bit, I don't think turbulence is the issue. Lots
> of pipe flows are turbulent because higher Reynolds numbers are
> associated with reduced friction factor (Take a look at a Moody
> diagram). The big issue is making sure the flow is straight and a
> uniform velocity profile is established. Fittings cause swirling and
> large scale eddys which affect flow measuring devices. The 12
> diameters is needed to straighten the flow and straighten a skewed
> velocity profile. Screens can do it but there's a pressure loss.
"Straightening Tubes" are often offered as a solution but I've never seen them used. Perhaps this option is industry-specific.
Paul Received on Sat Feb 23 00:14:00 2008
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