Velocity Calculation

[GladwinJay]

I have a 5/16" I.D. tube with (27) 1/32 holes equally spaced along the entire length. It is used to move plastic cups. What I need to determine (roughly) is the velocity of air coming out of each hole with approx. 100psi shop air being applied to the tube.

Actual number or just a formula is what I need.

Thanks in advance,
Jason
Huhtamaki Plastics

 

[zdas04]

Since the sum of the cross-sectional area of the 27 holes is about 1/5 the area of the tube, if you can disregard the dP through the length of the hole you should have choked flow out the holes and any choked flow calculation methodology would work.

Problem is that with holes that small, you really can't disregard the pressure drop through the pipe walls (if you could, then the air stream out of the holes would be really noisy at sonic velocity). I don't have an equation that describes pressure drop over a distance that short.

David Simpson, PE
MuleShoe Engineering

http://www.muleshoe-eng.com

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