control of over pressure in a waveguide assembly

[franck]

Hi all,

To avoid condensation within my waveguide (kind of pipe) assembly, I have to inject N2 gas. However, I have some very sensitive hardware attached to my waveguide (pressure window) which can hold a big pressure. Thus, I have a tight requirement to inject that GN2 in the pipe not to exceed an overpressure above ambient pressure of 0.5mbar, which very small knowing that the most acurate pressure regulator I was able to find can control the pressure to 70mbar!

I was advised to use a flow meter in series with the pressure regulator to achieve the requirement but I am not sure how to make my design. Really:

1-How do I find the flow needed to get my required over pressure in my cavity assuming this one has a given volume V of 30 cm3?

2-How do I make sure that I really get the wanted pressure in my pipe?

Best regards,

Franck

 

[sailoday28]

Prior to injection of N2 what are the initial conditions in the closed cavity?
ie,
Temperature, pressure, components of gas mixture (mole fraction)
Does overpressure requirement mean max of 0.5mbar greater than ambient? If so, what is ambient pressure or range of ambient pressure?

 

[franck]

Hi Sailoday28,

At the beginning the cavity will be filled in with air. The temperature will be close to 20C and the internal pressure close to 15 PSI.

The requirement as I understand it is to be 0.5 mbar above 15 PSI. I will put some heaters on my assembly to make sure the temperature does not change too much since it is likely to go cold so internal pressure should remain fairly constant.

Last thing, we can provide an input pressure to the flow meter of 5 PSI.

Franck