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water flowrate change from 1" pipe to 1/2" meter section

water flowrate change from 1" pipe to 1/2" meter section

water flowrate change from 1" pipe to 1/2" meter section

(OP)
is it possible to calculate the change in flowrate in a full 1" pipe if you take out a 1.5' section and replace it with 1/2" pipe, a flowmeter, and 2 quick disconnects? All I need to know is if I put this into the system will it change the flowrate significantly (more than about 5% change)?

all I know is flowrate is currently 6gpm... I feel like a retard for asking this because I looked around online for 3 hours already trying to figure this out but I obviously need help in fluid mechanics....

is the only thing I need to know the Cv factor for the flowmeter and quick disconnects? I know Cv factor for the quick disconnects is 3.2 each. Would it be reasonable to say that the friction from the small pipe section would be negligable? I am trying to think about this using the energy consevation equations

They say in the manual for the 1-10gpm flowmeter that the max pressure drop in 10:1 range is 8psi... can I get that the Cv factor is then 3.54? using Cv=Flowrate*(sqrt(spec gravity water/ 8psi))

even if I have all the Cv factors I still dont understand how to figure out how the flowrate changes...

maybe someone can help me or just suggest something that will clear this up... I already tried reading the crane 410 paper... I think that will be good once I understand things better

RE: water flowrate change from 1" pipe to 1/2" meter section

Think about your resistance:  

What is the ID of the original 1" pipe (hint: you need to know what schedule pipe both are - or measure both - but do NOT "guess") and of the new 1/2" nominal pipe?

The Quick Disconnects will be a small factor compared to the pipe dia change.    The pressure loss of 8 psi in that small of a flow meter doesn't make sense.    Check it again.    

RE: water flowrate change from 1" pipe to 1/2" meter section

USAeng
Will depend on what is pushing the fluid through the pipe; is it a centrifugal pump?, Positive displacement pump?, gravity flow, etc.

If for instance it is a PD pump, the flow won't change, just the pressure profile.

If it is a centrifugal pump, then you would have to look at the pump curve and take a look at the system, i.e. what is it pumping against?, what fluid?, elevation change?, suction pressure?

I don't have a book in front of me but 6gpm doesn't sound like friction would be too great

RE: water flowrate change from 1" pipe to 1/2" meter section

"will it change the flowrate significantly?"

- If it is a PD pump then DubMac has answered it.

- If it is a centrifugal pump then it depends on how long the original 1" pipe was. If it was 2 ft long and you replace 1.5 ft with 1/2" pipe it will have a significant effect. If the 1" pipe was 1000 ft long it will have a very small effect.

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