Restricted orifice

[anber]

well we have a system with pump and multi-branches , one branch has flowrate of 17 and pressure of 4 bars ,, we need to decrease the pressure to 1 bar so we use a restriction orifice , now does the flow rate will be affected ? if the application at the end of the branch needs the flowrate of 17 exactly

 

[MikeHalloran]

Seventeen exactly of WHAT? Acre-feet per fortnight?

Yes, the flow rate will be affected when you insert an orifice.

Is a flow regulator available in an appropriate size?

If not, in the general case, you need to model the entire system, first so that the model mirrors all of the important behaviors of the current real system, then apply changes to the model to get the desired behaviors, and hope that the model is actually good enough to predict the real system's new behaviors.



Mike Halloran
Pembroke Pines, FL, USA

 

[anber]

flow rate is 17 m3/h and i already made the whole system on the pipenet programe and one branch has this excess pressure , so i need to reduce the pressure only on this branch whithout affecting the flow rate

 

[LittleInch]

In a network I don't think it is possible to do that. Change one aspect of one branch and the whole network balance changes

Change the pressure you will change the flow.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[anber]

Let me clarify that this branch is not the critical branch , this means that there is another branch that has the heighest head at which the pump respond to it . The branch i am talking about is not the critical branch so it will have excess pressure ,, now we use the orfice which decreases pressure and according to continuity equation , the flow rate is constant which means what enters the orfice must leave the orfice , am i missing something ?

 

[EloyRD]

You have to work backward from your requirement.

You have a point where you have a requirement of xx l/s @ yy bar (only stating flow is incomplete information). If you are supplying to a sprinkler, an orifice, a heat exchanger, or a hose, pressure is linked to flow.
Then you have to add losses up to your manifold or fluid source. If you restrict by an orifice, flow and pressure will change both.

Changing one branch will change the whole demand curve and the flow-split-proportion.

 

[LittleInch]

The point is that unless your 17m3/hr is somehow unaffected by the pressure in that branch, as soon as you reduce the pressure in the branch then the flow rate will reduce in most instances.

So "so I need to reduce the pressure only on this branch without affecting the flow rate " is rarely possible in practice.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[mech212]

If the branch you are talking about is not critical branch , so the pump will produce head and flow rate as determined and since head doesn't change , so the point of the flow rate on the pump curve will not change also , so it will produce same flow rate , now you have two paths the critical path and the path you use orfice , the flow rate will be divided according to lenghts of pipes and resistances of fittings and may decrease from the critical path and increase in the path that contains orfice , but the total flow rate from the pump is constant in this case , what only changed is how they will be divided in your different paths

 

[LittleInch]

If you can reduce the pressure by exactly 3bar then the flowrate should stay the same providing your end point pressure in that branch reduces by an identical amount.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.