In vacuum systems, why is it required that the angle of the atmospheric leg not exceed 45 degrees or 30 degrees?
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This post was last edited by What is this of mine? on 2022-4-12 06:30. Dear sea friends, why is it required that the angle of the vacuum system and atmospheric legs should not exceed 45 degrees or 30 degrees?
What are vacuum systems and atmospheric legs? ? ?
Nonsense; even if it’s defined that way in the standards, it’s still nonsense—of course, this is conditional; saying it’s nonsense according to the standards is because it’s treated as a general rule! Another point is that, even when tilted, the water inside the atmospheric leg will still flow throughout the entire pipe… You need to understand that when a large amount of water is discharged, water and air must exchange simultaneously inside a vertical atmospheric leg; the water flowing out under the effect of gravity and the compression of the space inside the pipe as a result of this discharge occur in opposite directions! So, it depends on how much water is discharged, as well as the diameter of the air leg and its design!
Thank you very much. Are there any specific papers on this topic? Want to learn *it a bit? Or could you please explain again from what perspective this requirement is taken into account in the standards?
When the discharge volume is high, as you mentioned, the liquid column compresses the gas inside the tube, which doesn’t it result in a plunger flow that can no longer proceed? During the design of atmospheric legs, how are the liquid discharge rate within the pipes and the pipe diameter taken into account?
Plunger flow can also be expelled; the molecular forces between liquids are weak, and under the pressure difference between the top and bottom, bubbles or flow channels similar to vortices form through this plunger... However, this causes instantaneous pressure fluctuations in the vacuum pressure above the atmospheric leg, and these fluctuations can be quite significant. Draining downward involves quite a lot; you need to refer to materials related to fluid mechanics for this
It involves considering plug flow in order to design the discharge system for pipes that are not completely filled… But this is an ideal approach; moreover, it results in a significant reduction in the amount of water that can be discharged – which means that a larger diameter pipe is required for the downward discharge. But this depends on various factors, mainly whether the vacuum changes significantly over time or remains relatively stable However, this again relates to the vertical height of the atmospheric leg itself. It’s still quite complicated; it can’t be explained in just a few words
Oh, thanks for the explanation. I’ll study it again*