Limit suction from a fan in an air extraction system.

[WelshEngineer87]

Hi all,

I'm currently designing a test rig to measure air temperature of an enclosure with a heat source coming from inside the enclosure, airflow will be measured just upstream of the enclosure with a pitot tube and a centrifugal airflow fan upstream of the pitot tube.

On the outlet of the enclosure the outlet piping has to connect to an extractor system, which is ≈2m from the outlet of the enclosure to the extractor pipe inlet. There is no other way to evacuate the air inside the enclosure from the test chamber other than the extractor system.

The force of the airflow from the enclosure is not that powerful but i want to limit any effect it has on drawing air out of the enclosure and rely only on the compressor and pitot tube at the inlet for controlling airflow.

What are the options for limiting the effect of the extractor system on drawing air from the enclosure?

I have considered the following options:

- Large tank with an orifice / hole between the outlet of the enclosure and the extractor
- Long pipe between the outlet of the enclosure and the extractor
- Leave a gap between the exit of the enclosure outlet pipe to the entry of the extractor pipe.

 

[hacksaw]

what is the line/duct shape and size, materials of construction as there are a variety of louvers, you may need some distance between the fan and your pitot measurement, to insure uniform flow profile

 

[LittleInch]

Can you stick a VFD on the exhaust fan and control on pressure at the outlet so the fan only draws air away at exactly 1.00 bara regardless of air flow in?

Drawings or sketches with dimensions always helps.

Your incoming airflow doesn't look stable so a single pitot tube may not measure air flow properly.

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