Water distrubution system design

[qaliq]

I am trying to design a water distribution system which basically consists of a horizontal pipe (dia 300mm) with 6 vertical outlets. I know the total flow rate required and that the flow out of each pipe must be equal. how do i determine the diameters of the pipes? I know that I can use continuity (Q=uA) but I'm not sure how to relate the velocity in the horizontal pipe just before the outlet with the velocity of the water in the actual outlet.

Hope that all makes sense! Any help would be much appreciated

Thanks

 

[stewartcs]

how do i determine the diameters of the pipes?

In relation to what?

I know that I can use continuity (Q=uA) but I'm not sure how to relate the velocity in the horizontal pipe just before the outlet with the velocity of the water in the actual outlet.

If you use the continuity equation you have,

Q = v1*A1 and Q = v2*A2 which gives,

v1*A1/A2 = v2

So the velocity using continuity is related by the ratio of pipe diameters.

 

[Q_Goest]

Hi qaliq,

I am trying to design a water distribution system which basically consists of a horizontal pipe (dia 300mm) with 6 vertical outlets. I know the total flow rate required and that the flow out of each pipe must be equal.

If you're really trying to get exactly the same flow out of each pipe, and assuming the pipes are different lengths and potentially different elevations, then trying to size just a pipe to give you exactly the same flow (or even very close) will be difficult if not impossible to get right. You can get to maybe within plus or minus 10 or 20% at best.

I'd suggest simply putting a valve on the end of each pipe, and designing the system such that the dP through the pipe is relatively small compared to the dP through the valve. This way, you can adjust the valve without significantly altering the other 5 lines to get the exact flow you want from each pipe.

You might want to offer a bit more detail about what you're attempting to accomplish. It's harder to give advice when you don't understand the intent.