Why does measuring water flow differ between flowmeter and timed volume methods?

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capterdi
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I´m wanting to somehow demonstrate that if we measure the water flow on the header according to squetch for “Case 1” (see attached PDF) using a flowmeter previously installed, we are not going to get the same number for the GPM as if we proceed according to squetch for “Case 2”, where in order to “spare the cost of a flowmeter”, we disconnect the hose, direct the water flow into a deposit, and measure time elapsed via a stopwatch. Here, according to the volume of the deposit, and the elapsed time, we calculate the GPM. If we are discharging to the atmosphere we are getting rid of the losses that represent the nozzle, which has a number of holes drilled on it´s top plate. So I was wondering if there is a table somewhere on the net which would show the “equivalent lengh of pipe” for different kind of nozzle arrangements.

Thank you.
 

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capterdi said:
I´m wanting to somehow demonstrate that if we measure the water flow on the header according to squetch for “Case 1” (see attached PDF) using a flowmeter previously installed, we are not going to get the same number for the GPM as if we proceed according to squetch for “Case 2”, where in order to “spare the cost of a flowmeter”, we disconnect the hose, direct the water flow into a deposit, and measure time elapsed via a stopwatch. Here, according to the volume of the deposit, and the elapsed time, we calculate the GPM. If we are discharging to the atmosphere we are getting rid of the losses that represent the nozzle, which has a number of holes drilled on it´s top plate. So I was wondering if there is a table somewhere on the net which would show the “equivalent lengh of pipe” for different kind of nozzle arrangements.

Thank you.

I'm not sure what you are asking. You want to calculate the flowrate of the water in case 2 by measuring the time it takes to fill the container? Or, you're trying to calculate the flowrate in case 1 by using the method in case 2 and need to know the discharge coefficient for various nozzles?

CS
 
stewartcs said:
I'm not sure what you are asking. You want to calculate the flowrate of the water in case 2 by measuring the time it takes to fill the container? Or, you're trying to calculate the flowrate in case 1 by using the method in case 2 and need to know the discharge coefficient for various nozzles?

CS

What I would like to know is the discharge coefficient for various types of nozzles.

Thank you.
 
CS,

OK. I´ll take a look to that source and see what I find.

Thanks.