Pressure and flow rate relationship

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Discussion Overview

The discussion revolves around the relationship between pressure and flow rate in pipes, specifically examining how changes in flow rate affect pressure. The context includes both theoretical considerations and practical applications related to fluid dynamics.

Discussion Character

  • Technical explanation
  • Debate/contested
  • Homework-related

Main Points Raised

  • One participant questions whether the pressure will be 27.5 psig if the flow rate drops from 8000 gpm to 4000 gpm, given an initial pressure of 55 psig.
  • Another participant suggests that if the flow is turbulent, the pressure drop will be more than half but less than three-quarters of the initial pressure, indicating a non-linear relationship between flow rate and pressure.
  • A separate inquiry is made regarding the calculation of flow rate for air through a 12 mm diameter pipe at a pressure of 7 kg/cm², seeking to understand the volume of compressed air that could pass through in a minute.

Areas of Agreement / Disagreement

Participants express differing views on the relationship between pressure and flow rate, particularly in turbulent conditions. The inquiry about air flow rate introduces another aspect of the discussion, but no consensus is reached on the specific calculations or outcomes.

Contextual Notes

The discussion includes assumptions about flow conditions (turbulent vs. laminar) and lacks detailed mathematical derivations or definitions that could clarify the relationships discussed.

mfholbac
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If I 8000 gpm flowing in a pipe, and know that pressure of the water is 55psig, will the pressure be 27.5psig if the flow rate through the same pipe drops to 4000gpm.
 
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Hi mfholbac. Welcome to Physics Forums.

I assume you mean that the inlet pressure is 55 psig, and the outlet is into the atmosphere at 0 psig. If the flow is turbulent, which I assume will be the case in your system, then the pressure will drop more that just half-way, but a little less than 3/4 of the way.

Chet
 
Sir, Kindly let me know how to calculate flow rate (cfm or Litre/m) of air flowing through a pipe of 12 mm dia from a reservoir at pressure 7 kg/cm2 to atmosphere.

i.e ;- how much volume of compressed air could pass within a minute through a "X" mm dia pipe from a constant pressure (7 kg/cm2)
 
MANPREET SINGH said:
Sir, Kindly let me know how to calculate flow rate (cfm or Litre/m) of air flowing through a pipe of 12 mm dia from a reservoir at pressure 7 kg/cm2 to atmosphere.

i.e ;- how much volume of compressed air could pass within a minute through a "X" mm dia pipe from a constant pressure (7 kg/cm2)
This thread is over 2 years old, with no new responses. Please start a new thread. I am closing this one.

Please put your new thread in one of the homework forums, and use the template. Also, please do some literature search on your own before posting, to get an idea how to address a problem like this. The homework template will ask you to show your thinking and effort so far.

Chet
 

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