Pipe loss 4

[Yasinengineerman]

Which one is correct a or b.. Considering all 4 nozzles should discharge 5 gpm at 10 psi of pressure simultaneously...

 

[LittleInch]

Neither, but B is closer.

Sprinklers are variable flow depending on pressure, so in B the first sprinkler will flow more than 5 gpm which impacts on flow.

Also if those sprinklers are evenly spread, the pressure drop will vary as the flow goes down.

The best way is to either do iterations or design a a larger header pipe to reduce frictional loses.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[EdStainless]

If your pressure drop estimates are correct then the nozzle pressures will be 13, 12, 11, 10 and the flows will be whatever correspond to those pressures. And the source pressure will be 15.
The only way around this is to make the header large enough so that there is no pressure drop between nozzles. Or a large header and then equally restrictive drops to each nozzle.

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P.E. Metallurgy, consulting work welcomed

 

[Yasinengineerman]

@littleinch thankyou.. Actually I don't need the nozzles to discharge 10 psi.. Was making an excelsheet for Darcy wisebach method pressure drop calc. And got curious if for example there are 10 nozzles and each needs 10 psi so do we need to multiply the pressures.. Thanks for clarifying

@edstainless.. Nice explanation.. Thanks

 

[fel3]

Yasinengineerman...

Instead of building a spreadsheet, you might want to try EPANET, which is free water modeling software:

https://www.epa.gov/water-research/epanet

EPANET can use Darcy, Hazen-Williams, or Mannings for pipeline hydraulics and can model emitters for fire protection systems and irrigation systems. EPANET doesn't have all the bells and whistles that the commercial programs have (many of which use EPANET as the calculation engine), but it's a lot more usable and flexible than a spreadsheet can ever be.

Fred

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"Is it the only lesson of history that mankind is unteachable?"
--Winston S. Churchill

 

[1503-44]

No you do not multiply. You size the pipe, adding flow from each sprinkler, so that at least 10psig is available at each sprinkler.