Water flow through an orifice

[mdossaji]

I have a test setup. See attached document. I need to set my pressure gage such that my water flowing out of the nozzle (.04 in orifice) will maintain .63 gal/min at 150 ft/sec. I tried the bernoulli's equation but the number seesm to high like around 260 psi. My recollection was 35 psig but not sure how that number came by.

 

[Pumpsonly]

your nozzle dia. given in the post is different from the diagram.

you can not fixed the flow rate, velocity and nozzle dia. all at the same time.
Velocity = Q/Area. You have to decide which 2 values you have to achieve then calculate the 3rd.

Use the simple calculation as follow:
At the exit of the nozzle all the static energy (static head) will be converted into dynamic head = velocity head of the water jet.
Use the formula H=V(sq) / 2g.
Required gauge pressure= H / 2.31 (PSI.
This is without considering the discharge co-efficient of the nozzle/ orifice.

Hope this will help.