Pressure/GPM/Diameter Calculations

  • Context: High School 
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Discussion Overview

The discussion revolves around calculating the flow rate in gallons per minute (GPM) for two different pipe sizes (3/8" ID and 1/2" ID) under specific pressure conditions (26 psi and 17 psi, respectively). The context includes practical applications of fluid dynamics, particularly in relation to water flow through pipes without restrictions at the outlet.

Discussion Character

  • Technical explanation
  • Homework-related

Main Points Raised

  • One participant seeks assistance in determining the GPM for two pipe sizes given their internal diameters and operating pressures, expressing difficulty with existing formulas.
  • Another participant suggests using online calculators for pipe flow calculations, providing a specific website as a resource.
  • A participant reports using the recommended calculator and provides calculated flow rates and pressure drops for both pipe sizes, indicating 2.9 GPM for the 1/2" pipe and 1.3 GPM for the 3/8" pipe.
  • The same participant mentions the Hazen Williams formula as an alternative method for those who prefer not to use online calculators.
  • A later reply indicates that the original poster feels they have gained some understanding of the principles involved after receiving help.

Areas of Agreement / Disagreement

There is no explicit consensus on the calculations, as the original poster expresses confusion despite receiving suggestions and calculations from others. Multiple approaches to solving the problem are presented, but no definitive agreement on the methodology or results is reached.

Contextual Notes

The discussion lacks detailed assumptions regarding fluid properties, flow conditions, and the specific application context, which may affect the accuracy of the calculations. The reliance on online calculators and formulas introduces potential variability in results.

ISX
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I have been searching for a long time and can't figure this out. The formulas I find are way over my head.

Anyhow, I am trying to find how much flow would go through 2 different sized pipes. One is 3/8" ID and the other is 1/2" ID. The 3/8" uses 26psi and the 1/2" uses 17psi. All I want to know is the GPM each one will flow. I noticed there was a lot about constant of liquids so just use water. As for pressure drop stuff, there is a pump drawing in water and the pipes are on the other side and they have no end on them, so they are just shooting the water out like a hose with no end on it.

Thanks for any help I can get on this. Sorry if it is a dumb question.
 
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Bob S said:
Go to http://www.pipeflowcalculations.com/

Click on one of the online calculators on the left-hand side.

There are also other on-line calculators on the web.

Bob S

I have gone through that one and many others and I just can't figure them out.
 
ISX said:
I have gone through that one and many others and I just can't figure them out.
I used the calculator I recommended, and got the following numbers for the pressure drop per 100 ft of pipe:

1/2" pipe, 2.9 gpm, pressure drop=17 psi per 100' of pipe

3/8" pipe, 1.3 gpm, pressure drop=24 psi per 100' of pipe.

If you wold rather not use an online calculator, you can use the Hazen Williams formula at http://www.engineeringtoolbox.com/hazen-williams-water-d_797.html

Bob S
 
Ah that works. Think I halfway understand the principles now too. Thanks for the help!
 

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