Formula to calculate psi required to deliver gpm through nozzel

[SALTYFRIES]

I need to build a device to test the water resistance of a piece of restaurant equipment. The device must deliver 2.5 GPM of water through a nozzel with an opening of 2mm. Can someone please give me a formula to calculate the required PSI to deliver the needed volume of water?

Thank you.

 

[Aero51]

The answer to that question largely depends on the configuration of your set up. How much experience do you have with fluid mechanics? For starters, the mass flow (your GPS) is equal to the velocity of the fluid times the cross sectional area of the pipe times the fluid density.

 

[SALTYFRIES]

I am mostly mechanical and have almost no experience with fluid mechanics. I experimented with 3/4 diameter garden hose, connected to the city water supply, on the end of which was a cap with a drilled 2mm hole. I currently have no practical method to check the pressure of the supply but it delivered 91oz of water per minute, much less than the 320 required. I then had the idea to fill a pressure tank with water and connect compressed air to the tank to increase the pressure, but I do not know how to calculate how many psi would be required and so can't determine if that might be a feasible solution.

 

[256bits]

Look up orifice flow.
Here is one site with a limited free trial use of a calculator and some explanation to get you started. Check others out for more info.
http://www.efunda.com/formulae/fluids/calc_orifice_flowmeter.cfm#calc
Note that P2 would be atmospheric so the delta P is the supply pressure.

 

[jakestenson]

Here's some information about orifice calculations