What is the negative pressure level generated by a vacuum pump or ejector for vacuuming?
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Is the magnitude of negative pressure related to the pipe diameter?
How should I put it? ! The diameter of the pipe determines the level of resistance it presents; this remains the same when the flow rate is constant! Thin tubes have high resistance, while thick tubes have low resistance. In other words, with the same pump in a vacuum environment, when it is connected to your system through these pipes, the pressure in your system will be lower if using the larger pipes ； The pressure in your system with fine tubes is a bit higher.
Both water ring vacuum pumps and ejectors have operating curves. The curves from different manufacturers are similar; for the same device, as the pumping volume decreases, the vacuum level increases. Of course, every device has its limits. Over a decade ago, the water ring vacuum pumps produced in Foshan had very high performance levels; I’m not sure who makes better ones now. To obtain the product manual from the manufacturer, they are usually very willing to mail it to the designers.
The vacuum equipment is very close to the container being evacuated, and the flow rate in the pipes (where the vacuum level is high) has been reduced to a very low value – 1–3 meters per second; as a result, the pressure drop caused by changes in pipe diameter is minimal. It is necessary to calculate exactly how much.
At extreme vacuum, it is independent of the tube diameter.