Non-isothermal

General discussion
1

I checked webner in document section of MOLFLOW. There I can see the non-isothermal discussion section is not highlighted. Is it private?

I want to know about details on non-isothermal technique. How it implement in MOLFLOW+ and how the result will predict and benchmarked with analytical method.

How, P1/P2 and root T2/T1 calculate and relates with one another?

What is the temperature’s role in MOLFLOW+, if we change why pressure changes very less? Is there any possibility to a relationship between outgassing rate and temperature in MOLFLOW?

If possible kindly give some details on it.

Thankng You

Dr. Sabbir Ahmed.

2

Hello Sabbir,

This document explains how temperature plays a role in Molflow.

Relevant sections: “2.3 choosing particle speed”, “2.7 rebound”, “2.8.0.2 Pressure”

It has been benchmarked and corerctly give the p1/p2=sqrt(T1/T2) and n1/n2=sqrt(T2/T1) in case of two non-isothermal volumes in equilibrium connected by a pipe.

“What is the temperature’s role in MOLFLOW+, if we change why pressure changes very less?” Could you give an example where the change is not as expected?

“Is there any possibility to a relationship between outgassing rate and temperature in MOLFLOW?” - there certainly is, the incoming particle flux is directly governed by temperature, using the ideal gas equation d(pV)/dt=dN/dt*kT

3

“What is the temperature’s role in MOLFLOW+, if we change why pressure changes very less?” Could you give an example where the change is not as expected?"

In our experiment, We observed that at ambient temperature (T=298K), the pressure of the system is 2.5x10E-9 mbar. But when the temperature increases from 298K to 303K, the system’s pressure shows 3x10E-08 mbar. However, The molflow does not show any changes of order. Therefore, Is there any option in MOLFLOW that solves this kind of problem?

Thanking You
Sabbir

4

I guess in your experiement the icnreased pressure is due to increased outgassing.
Since Molflow takes outgassing as a user-defined parameter, you would have to account for this.
As said, the user-defined outgassing is converted to a particle flux with ideal gas equation. If you increase the temperature but don’t increase the outgassing, the particle flux will decrease as T is in the denominator.
Molflow correctly takes into account temperature on a molecular dynamics level, but it doesn’t govern outgassing, as it is a material property.