Initial pressure inside a structure (MolFlow+)

General discussion
1

Hello,

I would like to ask if it is possible to set a certain pressure level within a structure at the start of a simulation?

So i.e. to simulate the pumping down with a turbo pump which will only be started at a pressure of 1E-2 mbar!

Thanks in advance,

Oli DC

2

This thread looks fairly dead, but I am coming up against the same challenge. Will a solution be forthcoming?

3

Dear Oli and Matt,

To condition the system to an initial state, use a time-dependent outgassing that desorbs some particles in the beginning, optionally with a “valve” facet that has time-dependent opacity to contain particles to the desired volume.

As vacuum systems are linear, with one scaling step you can find the exact outgassing value that achieves the required target pressure.

Use the Pressure evilution plotter to monitor the pressure buildup in the initially pressurized volume, and open the valve when the pressure has stabilized.

If you need a step by step guide, let me know.

4

Hi Marton, Could you please share a step by step guide for the solution ? Thank you.

5
  • You would need to create/use a facet that will serve as gas source -> for its outgassing value, give a parameter name, for example "outgassing1".
  • You will also need to delimit the initial volume by a valve facet (so the initially injected gas won't escape to other parts of the system) -> let its opacity value be time-dependent as well, let's say "valve1"
  • Now you have to control these two facets in the parameter editor (Time / Edit Parameters):
  • Let Outgassing1 be a parameter of pulse desorption. For example, at moment 0, let its value be 1, and at moment 1E-7 s, let its value be 0. That way all molecules will be inserted at the very beginning.
  • Depending on the size and gas type of your system, the initial volume will need some time to reach equilibrium. Until that happens, keep the valve closed. Therefore the parameter "valve1" would be defined as 1 (total opacity) at moment t (if t is the time when equilibrium is reached), and 0 (full transparency) shortly after. If, for example, the valve opening moment is 1s, then the parameter would look like this: 1s -> value 1, 1.0001s -> value 0
  • Screenshots:

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6

Thanks for your fast reply. Can you suggest solution for the application in the att.?