As shown in the figure, will a siphon effect be formed?
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The equipment and pipelines are as shown in the diagram; the medium used is water. In a negative-pressure environment, if the liquid level in the upper container is below the upper discharge outlet, could siphoning occur at the lower level, thereby draining the liquid from the upper container?
No, the horizontal pipe inside the tank is there to prevent siphoning; even if both valves are opened, siphoning will not occur.
No, it won’t flow out once the liquid level drops below the inverted U shape
Oh, that horizontal pipe – isn’t it the overflow pipe?
But in reality, the liquid level inside the container occasionally drops below the level in the high-level tube……
That overflow pipe also serves to disrupt the siphon effect, as its height is above that of the discharge pipe, allowing it to balance with the air pressure above the tank. It’s actually the siphon pipe leaking air.
This post was last edited by qugd on 2019-3-21 at 10:40. When the liquid level is below the upper pipe, the opening of the upper pipe is in balance with the air pressure inside the tank; in other words, the discharge pipe at the upper overflow opening remains open, so no siphoning condition can be established. A special case is when the overflow pipe opening is blocked, which can lead to siphoning. This requires the upper part as well as the overflow pipe opening to have a larger diameter, so that the material cannot block them at all.
Well, it’s leaking anyway, so it can’t be siphoned either.