Re: Part full line - water hammer estimation

From: <Gordon.Reddek@Alcan.com>
Date: Thu Jun 17 2004 - 18:43:00 EDT

Steve,

Everything I would have said has been said, so no epistle. However the following: In the oil and gas business I have heard the term "slack section" used to describe the section of line where the flow breaks into two phase flow when the line dives over the top edge of an escarpment. You may find the terms "slack" and "two phase flow" or "multi-phase flow" useful when searching the web.

Cheers,

Gordon

Gordon Reddek
Specialist Mechanical Engineer
Alcan Engineering, Level 3, 443 Queen St, Brisbane, Qld 4001, Australia. Tel: +61 7 3328 6424
Fax: +61 7 3328 6990
Email: gordon.reddek@alcan.com

"Steve McKenzie" <mechproj@xtra.co.nz>
17/06/2004 08:23 PM
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[PipingDesign] Part full line - water hammer estimation

Gents + 1

I am looking at a water pipeline 2.8km long, flow rate 60l/s, ID 227mm.
The inlet is atmospheric from a tank. For the first 800m, the line drops 150m in elevation. For the remaining 2km, the line is near enough to horizontal, discharging into a pond. The friction loss under full pipe conditions will be about 30m (dirty). This means that the water will drop the first 120m (vertical) the line will run part full, with fairly high velocities. At the -120m point the line will become full with a fairly sharp head rise due to the sudden velocity rise forming a sort of hydraulic jump. I can take a rough stab at the part full velocity (using open channel flow theory) and I know the full pipe velocity. To get the surge rise, I thought I may be able to use Joukowsky's formula; delta H = a delta V /g; a is celerity. However, I think the result will be overly conservative,and would need to do a fair bit of work before being confident about the result. This is a fairly common operating condition, but I do not seem to have a clear estimation procedure for this.

Can anyone point me to a book or other reference?

Cheers

Steve

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Received on Thu Jun 17 18:43:00 2004