Calculating drop in gas pressure

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SUMMARY

The discussion focuses on calculating gas pressure drop using the Poles Formula, specifically for a flow rate of 6 m³/h, a pipe diameter of 20 mm, a length of 19 m, and a specific gravity of 0.58. The calculated pressure drop is 2.459 mbar, which aligns with expectations. It is confirmed that a higher flow rate results in greater friction and, consequently, a higher pressure loss, leading to the conclusion that a lower flow rate can indeed result in a higher pressure at the pipe's end, contrary to initial assumptions.

PREREQUISITES
  • Understanding of fluid dynamics principles
  • Familiarity with the Poles Formula for pressure drop calculations
  • Knowledge of specific gravity and its application in gas density
  • Basic skills in unit conversions (e.g., m³/h to mbar)
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  • Study the application of the Poles Formula in different gas flow scenarios
  • Research the impact of pipe diameter on pressure drop in gas systems
  • Explore methods to minimize pressure loss in piping systems
  • Learn about the relationship between flow rate and friction in fluid dynamics
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Engineers, fluid dynamics specialists, and anyone involved in the design or analysis of gas piping systems will benefit from this discussion.

Cardigan9
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Poles Formula (see page 10 of attachment)

www.mech.hku.hk/bse/MEBS6000/mebs6000_1011_04_steam.pdf

Where have I gone wrong?

• q = flow (m3/h)
• d = diameter of pipe (mm)
• h = pressure drop (mbar)
• l = length of pipe (m)
• s = specific gravity of gas (density of gas / density of air)

h = ( q^2 * s * l ) / ( 0.0071^2 * d^5 )

q = 6 m3/h
d = 20mm
l = 19M
s = 0.58

The result is 2.459 i.e. the pressure drops by 2.2459 mb, which on the face of it looks fine, the problem is that if I reduce the flow rate the loss of pressure over the length of the pipe drops. Which in theory means that if I start with 21mb gas pressure and have a lower flow rate I end up with a higher pressure at the end of the pipe; that can't be right can it?
 
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Yes, that is correct. Higher flow causes more friction and more pressure loss.
 

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