Pipe diameter calculation
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For a natural backflow pipe with a height difference and non-full-flow conditions, how should the diameter of such a backflow pipe be calculated?
Gravity flow? A rough estimate can be made using a flow rate of 0.5 m/s
For example, is this flow rate still applicable even if there is a height difference of four or five meters?
Well, that’s more or less the estimate
No way, free fall isn’t that fast.
This post was last edited by waaabc on 2016-7-25 at 16:03. See, it’s in a pipe, so there is resistance; even if you pour it into the air, air resistance is present, so it’s not complete free fall. Moreover, since you are using gravity flow, the fluid in the pipe is not at a full capacity.
As an estimate, for natural flow, use a flow velocity of less than 1 meter. If considering undersized pipes, it would be fine to use a coefficient for the diameter at that time, such as around 1.2–1.3
When calculating the diameter of gravity return pipes, a flow velocity of 0.5 m/s can typically be used.