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# maximum possible flowrate from an circular orifice with 15 millimeters diameter at 8 bar pressure

## maximum possible flowrate from an circular orifice with 15 millimeters diameter at 8 bar pressure

(OP)
hi
I wanna know how much is the maximum flow rate from an circular orifice with 15 millimeters diameter at 8 bar pressure?

### RE: maximum possible flowrate from an circular orifice with 15 millimeters diameter at 8 bar pressure

You're new so a few tips.

This is a site for professional engineers. "I wanna" is not the way to express yourself.

Demands for answers don't get far either.

Even if I could give you the answer there is insufficient data.
What fluid?
8 bar differential? Upstream pressure? D/s pressure?
Density?

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

### RE: maximum possible flowrate from an circular orifice with 15 millimeters diameter at 8 bar pressure

you'll need to provide considerably more detail to get any sort of a response, it is considered a relatively minor calculation

### RE: maximum possible flowrate from an circular orifice with 15 millimeters diameter at 8 bar pressure

(OP)
thanks for your comment.(you are right)
the fluid is water
8 bar differential
I do not know what do you mean by " Upstream pressure & D/s pressure " but the pipe and the orifice is horizontal
I used bernoulli's equation and the result was about 30 m3/h

### RE: maximum possible flowrate from an circular orifice with 15 millimeters diameter at 8 bar pressure

It makes a big difference to know your parameters.

If the differential pressure at 8 bar is 8 barg u/s and 0 barg downsteam you're in choked flow

Diff pressure of 8 barg with 20 barg u/s and 12 d/s you're not. You will get two different answers.

There are many online orifice calculations about, but chose one which is for choked flow.

I got a flow of about 17 m3/hr.

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

### RE: maximum possible flowrate from an circular orifice with 15 millimeters diameter at 8 bar pressure

(OP)
hi
actually I am setting up a water-foam fire fighting system for a warehouse that its area is 472 square meter and a device is introduced to me that its name is inductor which use venturi effect to suck foam by suitable ratio to make foam (type of foam is AFFF 3%)its main pipe is 2 " but it has a venturi orifice that its minimum section is 17 diameter.
it is installed horizontally at 4 meter height above the ground.a centrifugal pump produce 8 bar pressure and it has 3" outlet pipe.we have installed 12 pending foam-water nozzles with 3/4" inlet that need to have at least 5 bar pressure behind them to produce the right pattern when discharging the foam . Q = the amount of water volume the nozzle need and is calculated by {Q =K*[(radical)P]}(P=pressure)( K=45 is a factor related to the nazzle) so Q=12*45*2.23=1200 liters per minute or 72 cubic meter . (the piping line is a dry system) I am wondering if this orifice allow the amount of water through the pipe line? a few days later I can tell you what is the real test result because I`ve already installed the device by the force of someone who is responsible for this issue and I will test it. but I predict that it will not allow this amount of water through itself.that was the whole story...

### RE: maximum possible flowrate from an circular orifice with 15 millimeters diameter at 8 bar pressure

(OP)
because the piping line is dry so the differential pressure is 8 bar ( 8 barg u/s and 0 barg downsteam )

### RE: maximum possible flowrate from an circular orifice with 15 millimeters diameter at 8 bar pressure

Ok,

There's lots of things wrong with your thinking IMO

"{Q =K*[(radical)P]}(P=pressure)( K=45 is a factor related to the nazzle) seems to be based on 12 units with sqr root of 5 bar being used?? No idea where this comes from - needs to be backed up by vendor data.

An eductor as part of a venturi works differently to an orifice which is a sharp edge hole / plate usually.

Your pressure a short distance U/S and D/S of a venture should be nearly equal.

Your empty pipe scenario is not your sizing criteria. You probably need to be careful that your pump and motor can handle the excess flow you will get at until your system fills with water. If not designed with plenty of spare power you could easily trip the pump.

The device is an eductor and you really just need to look up the vendors data sheet to find out what its capacity is. From what I can see you need a 3" one.

This is a very common means to mix foam concentrate so the numbers will be well tested.

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

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