Hye,
I am not sure if this is the right place to ask this question, but I hope someone in the forum may answer this question.

I've posted a thread few weeks back regarding copper capillary tube. You see, I am actually writing a research project about capillary tube and its manufacturing.

Now I am stuck at the purging process with Nitrogen. Because of the small diameter of capillary tube and its quite thick wall thickness (often cap tube with dimension 1.9mm O.D x 0.6mm Wall thickness), and with 100 kilogram per coil, it will take 18000 MINUTESS!! to purge the inside of the cap tube with Nitrogen so to prevent oxidation from happening before being brought into the annealing furnace. I know in order for me to reduce the time of this, I can REDUCE the coil weight (so less length), and increase the Nitrogen pressure at the inlet. all of these is to reduce the manufacturing cost.

But I also notice, when I change the dimension of the tube, either the diameter, wall thickness or both, the purging time will also change. Now comes my dumb question. What should I look into, in terms of tube dimension, to see the trend of the increase / decrease in purging time?? I mean is there any ratio that I should look into to see the trend like for example the higher the ratio between the volume and wall thickness, the longer purging time needed? Something like that??

Is there any formula to present the pressure gas drop inside the cap tube?

Is there any way to purge Nitrogen inside the tube with less time?
Thanks!