Study on the Performance of Ventiflex Ducting and Couplings

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Study on the Performance of Ventiflex Ducting and
Couplings

• Göran Hansson and Lars Anisdahl (Protan)

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Ventiflex for mine and tunnel ventilation on a
global scale
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Objective with this study

• To assess the friction loss factors, the shock
  loss factors and the leakage factors for
  Ventiflex ducting with couplings.
• These factors are important design parameters for
  the whole ventilation system.
• Correct assessment of these factors provides a
  better design basis for Ventiflex systems, and
  makes it easier to optimise both investment and
  operating costs for the whole ventilation system.
  

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The Ventiflex coupling system
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Couplings
Steel-ring
Velcro
Zip
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Design parameters

• Friction factor
• This tells the magnitude of the friction loss
  between the flowing air and the inner duct wall.
• Shock loss factor
• This tells the magnitude of the sudden pressure
  drops at obstacles (bends, tees, contractions,
  diffusers, joints, etc.).
• Leakage factor, f
• This factor is the average area of leakages given
  in mm2 (in2) per m2 (ft2) duct wall.
• The total pressure at the duct inlet and the air
  flow rate at the duct outlet are governed by
  these three factors.

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The SIA norm (Swiss standard)
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Experimental programme

• Three straight ducts of length 400 m and diameter
  1200 mm.
• One with no couplings.
• One with Velcro couplings every 10 m.
• One with Zip couplings every 10 m.
• One duct length of 2720 m and diameter 1700 mm.
• Steel-ring couplings for every 10 m.
• Air flow rates and pressures were measured along
  the ducts.
• Based on the measurements, friction factors,
  shock loss factors and leakage factors were
  calculated.

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From the experiments
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Results Friction factor (K-factor)
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Results Shock loss factor
For comparison Shock loss factor for a bend or a
tee 0,2 1,0
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Results Leakage factor (mm2/m2)
No leakages
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Results
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Duct design using VentiflexCalc
Friction factor input
Leakage factor input
Shock loss factor input
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Summary

• Friction factors, shock loss factors and leakage
  factors have been assessed for Ventiflex ducts
  comprising velcro, zip and steel-ring couplings.
• The results confirm that the leakage is zero for
  correctly installed couplings in a well aligned
  duct, but it does not mean that there will be no
  leakages from any installed coupling.
• The Ventiflex system easily complies to SIA class
  S, or better.
• However, a Ventiflex system should always be
  designed according to the particular application.