1 reply to this topic

[Yusuf]

Hi
I would like to know the maximum flow when air at 105kpa gauge pressure is vented though a 10.5mm bore tube. Is there a simple formula that can roughly estimate this

[katmar]

There is no really simple formula for this because your fluid is compressible. If the pressure drop is less than 10% of the absolute pressure you can simplify by considering the fluid as incompressible. Unfortunately, here your pressure drop is 105/(105+101) x 100% = 51%, so you must take the change in density and acceleration due to expansion into account.

It also depends on the length of your tube. If it is very short you will get the added complication of choked flow.

For more detail Google for "isothermal compressible flow" and "choked flow". You will probably find information on those subjects by searching these forums.