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Gravity Flow through Side Exit Pipe

Gravity Flow through Side Exit Pipe

Gravity Flow through Side Exit Pipe


I am working with a cooling tower where the water outlet from the collection basin is a horizontal-side exit 14 inch pipe.  I am trying to get a handle on the flow rate through the exit as a function of the height of water filling the pipe.  The exit system is based on gravity flow.  After the exit, there is a 7 inch section of straight horizontal pipe followed by a 90 degree elbow straight down into a cooling water supply pit.  The pipe essentially behaves like an outlet weir.  Does anyone know of a reference where I can find some flow calculation methods for this scenario?

Thanks in advance,


RE: Gravity Flow through Side Exit Pipe

This was covered in a paper by PD Hills in Chemical Engineering Magazine, Sept 5, 1983, pgs 111-114.  Art Montemayor made a summary of this article in a spreadsheet which you will probably find if you google for "art's fluid flow".

In the past when I have needed rough heights I have approximated the pipe area with a trapezoidal weir. If you only need a +/- 20% answer this is good enough.  If you have only 7" of straight pipe before the down leg this approach should work. It depends on how accurate you want to be.

Katmar Software
Engineering & Risk Analysis Software

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