Flow, pressure, and pipe diameter?

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Discussion Overview

The discussion revolves around the relationship between flow rate, pressure, and pipe diameter in a fluid dynamics context. Participants explore how varying pipe diameters affect the gallons per minute (gpm) of water flowing through them, considering factors like pressure and other variables.

Discussion Character

  • Exploratory, Technical explanation, Conceptual clarification, Debate/contested

Main Points Raised

  • One participant asks about the expected flow rates in gpm for two pipes of different diameters at the same pressure.
  • Another participant notes that absolute flow rates cannot be determined without additional information, suggesting only relative volume rates can be discussed.
  • A different participant provides approximate maximum flow rates for both pipe sizes, indicating that the actual flow can vary widely based on several factors, including inlet and outlet pressure, fittings, elevation change, pipe material, and fluid type.
  • One participant emphasizes that the relationship between diameter and flow rate is not linear, pointing out that while a 10-inch pipe is significantly larger than a 1.25-inch pipe, the flow does not increase proportionally with diameter.

Areas of Agreement / Disagreement

Participants generally agree that additional information is necessary to determine actual flow rates, and there is a consensus that the relationship between pipe diameter and flow rate is not straightforward. However, there is no consensus on specific flow rates or the implications of diameter changes.

Contextual Notes

Limitations include the lack of specific details such as outlet pressure, fittings, elevation changes, pipe material, and fluid type, which are necessary for accurate calculations of flow rates.

Who May Find This Useful

This discussion may be useful for individuals interested in fluid dynamics, engineering applications involving piping systems, or those seeking to understand the principles of flow rates in relation to pipe dimensions.

davehans
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If I have water being pumped through two lengths of pipe, both at 50 psi, but one pipe is 1.25" diameter and the other is 10" diameter, approimately how many gpm will be flowing through each pipe? Thanks in advance!
 
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There is not enough information for an answer with absolute volume, but only relative volume rate.
 
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I can tell you that a 1.25" pipe will generally have a maximum practical flow of ~30-40 gpm and a 10 inch pipe will have a maximum practical flow of somewhere in the range of 2500-3000 gpm. However, each of these pipes can have any flow in between 0 and their maximum practical flow (and beyond, in some/many cases).

If you want to know actual flow, you need to provide more information, at least:
-inlet pressure (check)
-outlet pressure
-fittings? (valves, elbows, meters, etc)
-elevation change?
-Pipe material?
-Fluid type? (water? Syrup?)
 
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Thanks guys. Those numbers are close enough for me to have made my point in a discussion... the point being that 10 times the diameter is NOT 10 times the flow... :-) ......especially when we already know that double the diameter is 4x the flow...
 

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