Model leaks in tanks and valves in a gas SIMULINK system

Hi,

I would like to create a Simulink model to be able to study specific leaks in a gas systems, through Tanks, valves and pipes. I need to define the leak rates as typically STD Helium leak rates (but of course the actual leak will change in fonction of the delta pressure between the inlet and the outlet). I see that I can model restrictions for example, or small orifices or holes, but that would only work for static, constant leak (not delta P dependant), or I can't necessarily derive the hole diameter to the actual leak rate (which is the parameter I want to adjust): I should only know the STD leak rate. What would be the best way to do that with Simulink? Create specific objects like valves with another port used for leaks?

Thanks!

Samuel

[Yifeng Tang]

It sounds like you have some values as a "standard" leak rate, is that right? I would assume you also know the pressure difference where this standard leak occurs. If this is the case, you can use a flow resistance block to model the leakage. The standard leak rate and pressure difference can go directly into the nominal mass flow rate and nominal pressure drop parameters. You need to estimate when the flow is expected to turn turbulent and adjust the "Fraction of nominal mass flow rate for laminar transition" parameter.

At the same time, local restrictions should work, too. The flow rate does change as a function of pressure. You can use reservoirs to set up different pressures, measure the flow rate, adjust the restriction size until you get the target leakage.

[Samuel]

Thanks!! Yes I know the typical pressure difference for the known leak rate, so I will try your suggestion.

[Yifeng Tang]

Good. I'll move the comment to Answers then.

Answer 1

[Yifeng Tang]

(Moved to Answer from Comments)

It sounds like you have some values as a "standard" leak rate, is that right? I would assume you also know the pressure difference where this standard leak occurs. If this is the case, you can use a flow resistance block to model the leakage. The standard leak rate and pressure difference can go directly into the nominal mass flow rate and nominal pressure drop parameters. You need to estimate when the flow is expected to turn turbulent and adjust the "Fraction of nominal mass flow rate for laminar transition" parameter.

At the same time, local restrictions should work, too. The flow rate does change as a function of pressure. You can use reservoirs to set up different pressures, measure the flow rate, adjust the restriction size until you get the target leakage.