Discharge of a costant volume chamber

Hi all,

I'm modelling the discharge of a pressurized constant volume chamber at a specific temperature in the pneumatic domain. Here you can see the model:

The model works fine in charging, but not in discharging; the same the flow rate in charging is much higher than in discharging with the same valve area and pressure difference. Here you can see the pressure trend in discharging top and in charging bottom with the same pressure difference:

Charging:

Discharging:

As you can see in charging the max flow rate is around 2e-3 kg/s instead in discarghing is around -7e-6 kg/s (the pressure difference is the opposite than in the charging simulation) even if the valve area and pressure difference is the same. Should them be the same?

I'm attaching the model.

Any suggestion is appreciated.

Thanks

Thanks

[dpb]

I don't have Simulink and my eyes can't read the graphics but just a question that comes to mind...is the driving pressure really the same in discharge as in charge? It strikes me that there may be an external "push" that's there from the air source that isn't when discharging so that what you think is the same dP really isn't (except instantaneously at the initiation of discharge, perhaps).

I don't know that has anything whatever to do with the problem; just a thought reading the problem description...

[pietro]

Hi,

thanks for your reply. With such easy model I don't see any external "push".

Here you can see the model without the pressure source subsystem to make you to understand what there is inside it.

Here again the result plots with a better quality:

At the discharge the initial pressure of the chamber was 0.01 bar and at the outlet was 2.51 bar because I can't set a chamber pressure of 0 bar. As you can see in the charge the chamber pressure quickly reaches the outlet pressure. I checked with pressure sensor if the pressure difference was the same and it is. This issue is driving me crazy.

Answer 1

[pietro]

Hi,

solved the problem....it was due to a temperature difference between the chamber and the line. Thanks for your help

[Abhishek Vats]

Hi , i download this circuit but its not working can you help me to understand this and share the correct circuit @[e-mail] sir.