Dear Marton
I have one simple question.
I have watched your two videos in YouTube, and noticed that you used two method to calculate the conductance. One is the transmission probability, the other is the outgassing rate and pressure difference. I tried these two method for a simple Pipe, but the results are different.
I set the outgassing rate and sticking factor on facet 1 are both1, the sticking factor on facet 102(the other side) is 1 and no desorption.
A102/SUMDES*conductance of entrance = 0.12;
1/(P102-P1) = 9.26 = conductance of entrance.
I am confused. Is there anything missed?
The first formula is correct if the particle can exit at both sides of the pipe (so setting sticking=1 on both ends).
The second formula is correct if the gas flows from the higher pressure to the lower. This is not the case when sticking is 1 on both sides, as the majority of Q will exit at the entry point, and only a small fraction (the transm. probability) will exit on the other side.
I assume that in my video I didn’t have sticking on the outgassing (entry) location.
The second formula in case of multiple exits would be:
C=Q_through/(p_entrance - p_exit), where Q_through is Q_total*transm_probability
Below is a demo for a L/R=1000 pipe (click for full screen to read formulas):
Please note the small difference (0.91 vs 0.96) because the pressure calculation is not exact on sticking=1 facets, nor on desorbing facets (not isotropic condition, no force due to rebound, etc.)
