Water Flow Through Fixed Diameter Nozzle

A pressure gauge will have no effect; it is a measurement instrument.

Regulator, perhaps? Or, is this a red herring from your homework question?

The gauge is simply for measurement, and is actually placed between the nozzle and global valve.

I know that the 3/4" hose has a greater GPM flow rate than the 1/2" hose. But given that the nozzle opening size is fixed and the water between the nozzle and valve is 30psi in a fixed diameter fitting, the size of the hose on the other side of the valve should have no affect on the flow rate exiting the nozzle. Correct?

Yes. The flow rate will be affected.

There seems to be an adequate pressure reserve but it really depends on the distance of the hose.

The biggest confusion..... usually with students or very green engineers is that they confuse pressure and flow rate.

Remember, your only as strong as your weakest link.

In this case, You flow rate is only highest from you largest impediment, and it goes down from there.

Correct, there is plenty of pressure reserve, the 90psi does not matter. Also assuming no pressure loss due to the length of the hose.

GA

Engineeting Power Tools (Free Ware) can also help. The have a section on Orifice sizes and flow rates, based on head.

This question does not need to be answered quantitatively. Assuming there is adequate pressure reserve and that hose length is negligible. Will a greater diameter hose affect the GPM exiting the nozzle given the setup.

for a descrete answer........... yes

As long as you open the globe valve to provide the same 30 psi at the nozzle inlet, the flow rate will be the same.

Yes, the globe valve is opened just enough to provide a constant 30psi in front of the nozzle.

Thank you everyone for your feedback. Much appreciated.

No if the nozzle diameter is considerably less than your global valve port AND your supply hose; besides, you have a regulator (not a gauge, you can't "set" a gauge) which will self adjust depending on the demand in order to keep your desired 30 Psig.

If that's your case, I'd say it's ok for you to install a 1/2" hose instead of a 3/4" one.

Here is the setup (i apologize, should have provided this with the original question) : http://www.monarchmfgworks.com/shop/aama-kit-for-large-capacity-monarch-water-nozzle-b-25/

The nozzle diameter is significantly smaller than the global valve and supply diameter.

It is the same principle, except that you'll have to adjust the valve manually to compensate for pressure drops.

Your link relates to an AAMA test. The test for water is done with simulated rain fall with the device in the link. The simulated rain fall to be equivalent to 8 inch rain fall an hour. There are different size specs in the emitters(your nozzle). Sizes cover different area. Each are rated for GPM at specified psi. All you have to do is match the gpm to the chart given in a link of previous post on line losses.

Since most these run less then 2 GPM hose size only will be an issue if there are a lot of spray heads on a single line.

With a single 5 GPM @ 30 PSI nozzle, it just doesn't matter.

You could even use 1/4 " hose.