Flow through pipes and throttling valves .NEED HELP

[JPEng]

Flow through pipes and throttling valves...NEED HELP!

I need some help with a real-life problem

I have an open topped water collection tank at elevation. The water is distributed by gravity flow from the tank via a pipe to a lower elevation. At the point of delivery, the pressure head is 18psi. However I need to deliver the water at the same flow rate that is filling the tank but at a reduced pressure of 7 psi. Can i use a throttling valve to achieve this?

 

[A Fine Man]

not sure if this will help but flow rate is calculated as: Q=VA

so the flow rate Q is equal to the velocity of the water times the area of the head.



if the opening is round the area, A, is computed as:3.1415/4 * D^2


Also the equation for pressure is: P = F/A so in your case it would work out to

A* 7psi= F

Hope this helps you in some way.

 

[JPEng]

Thanks bro...although i understand flow rate calculations, I still can't relate it to the proposed throttle valve...would the flow remain constant after passing the throttle? Would there be a pressure drop across the throttle?

 

[R Power]

using a reducer or nozzle will lower the pressure head and flow rate will remain constant...
Throttle valve as far as i know, is a flow control valve, so will reduce the flow rate...Im not sure though.

 

[xxChrisxx]

As R Power says, use a nozzle to reduce pressure.