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Combining 2 different pressure penstock lines

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Mountain Clan:
I have 2 springs I would like to combine the flow of into one penstock pipe.

A lower and a higher (on the hillside) spring. The lower spring has 3-4 times the flow of the upper spring.
The higher spring is 40' above (vertical head) the lower spring, and the 2 springs are more than 350' apart horizontally.
If I combine the flows below the lower spring, then will the pressure in the penstock below that point balance to the pressure of the lower spring where it is combined?
Will the flow of the lower spring reduce at all because of mixing with the higher pressure of the upper spring ?

If I think about the interaction of the different pressure flows simply, then I guess that the pressure of the upper spring will go up the lower spring pipe from the combination point, until it reduces and balances with the lower spring pressure.

If you know about combining penstock pipes, please do let me know what you think.

richhagen:
I am no expert on pen stocks, but water will only flow from higher pressure to lower pressure.  While it is possible to use the energy in some of the water to power a pump to pump a small portion of the water uphill (or to higher pressure), it costs in efficiency if you are only planning to capture energy from that higher pressure water relative to just getting what you can out of it at lower pressure.   In your case, it would seem to me that likely the highest yielding energy capture would involve separate generators on each flow.  Hopefully someone with a bit more experience with a similar problem will chime in here.  Rich

SparWeb:
Penstocks are not in my personal experience, but what you're describing sounds possible.  It reminds of me of the "ejector effect".  A high pressure flow is directed through a nozzle that drives a low-pressure high-volume flow.  IIRC you can do it in a way that allows them to mutually reinforce the flow, but if you don't take care of some details they will interfere with each other instead.  See what you can find on the ejector effect and how to make it work for you... 

bigrockcandymountain:
Or just have a combination wheel hooked to the same generator.  The high pressure will be larger diameter smaller cups.  Low pressire will be a smaller diameter wheel with larger cups. 

mab:

--- Quote from: Mountain Clan on January 20, 2019, 04:19:35 PM ---If I combine the flows below the lower spring, then will the pressure in the penstock below that point balance to the pressure of the lower spring where it is combined?
--- End quote ---
yes


--- Quote ---Will the flow of the lower spring reduce at all because of mixing with the higher pressure of the upper spring ?
--- End quote ---
probably - unless the draw at the bottom of the penstock is matched to the combined flows from both springs


--- Quote ---If I think about the interaction of the different pressure flows simply, then I guess that the pressure of the upper spring will go up the lower spring pipe from the combination point, until it reduces and balances with the lower spring pressure.
--- End quote ---
yes


--- Quote ---If you know about combining penstock pipes, please do let me know what you think.
--- End quote ---
I've sort of done this unintentionally: my penstock had a single collection point where the two streams came together - just a simple strainer. I then installed a coanda screen about 2m (vertically) above the original strainer on one leg - but have not yet installed the coanda screen on the other leg (to be installed at the same height).

What happens in practice ATM is that the water from the coanda screen 'chutes' down the pipe to the lower strainer and comes out through the strainer (actually carries air down under the water with it and blows bubbles out through the strainer). The pelton wheel 'sees' the same pressure as it would see without the coanda screen collection point and will do so until I've installed the 2nd screen and removed the original strainer.

best answers are (as bigrockcandymountain said) two penstocks and two wheels, or (as richhagen said) two penstocks and two generators IMHO

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