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.
Christopher Wright P.E. |"They couldn't hit an elephant at
chrisw@skypoint.com | this distance" (last words of Gen.
.......................................| John Sedgwick, Spotsylvania
1864)
http://www.skypoint.com/~chrisw/
Received on Sat Feb 23 00:02:00 2008