Number of Holes for Spray Bar

[Scott Lewis <ScottWmLewis at attbi_com>]

> This was discussed briefly in the past, but it was never sufficiently
> answered IMHO. There has got to be some way to calculate the number/size
> of holes in a spray bar that one can have before the flow is no longer
> equal out of all of the holes simultaneously. It is true that this is a
> hydraulic flow problem, but it is not true that you can have an
> arbitrary number of holes and still get even flow.
>
> This is the same problem that I imagine engineers are faced with all the
> time. An example might be to figure out how many secondary water lines
> can tap into the main and keep each secondary receiving equal flow.
>
> I don't mind researching this myself, but I do need a little help
> getting off in the right direction. I don't even know what you call this
> kind of problem, so searching is difficult.
>
> Anyone?

You might try hydrodynamics.

Heck, this is the same kind of problem big companies employ supercomputers to simulate,,,
sort of.

If you truly want to have equal water flow out of each hole in the spray bar, you need to
have variable diameter tubing and/or outlet holes.  You have the problem as I believe you
know of dropping pressure as you move away from the pump and along the plumbing and at
each outlet.

This would be a very doable calculation except for one thing, turbulence.  There is one
way around this.....make the plumbing large compared to the water flow and outlet holes.
If you have a 1" diameter pipe with 1/32 or 1/16 inch outlet holes, you minimize the
effects of the turbulence by reducing the flow rate in the pipe.

Even if you were to use a relatively small pipe and varied the outlet hole size for equal
flow volume, you would still end up with a difference in flow velocity for each of the
holes.  If you want equal flow volume AND velocity, then you are back to using a large
enough pipe to minimize the pressure drop across the length of the pipe.


--
Scott

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