Piping design: pipe flow v.s. open channel flow ?
Piping design: pipe flow v.s. open channel flow ?
(OP)
Hi All,
For designing a liquid flow collection and distribution network, under what condition is open channel flow better than pipe flow? Does open channel piping also need pumping or the increased elevation at one end will work? And how do you decide whether to use circular pipes or rectangular pipes?
Thanks,
EngReno
For designing a liquid flow collection and distribution network, under what condition is open channel flow better than pipe flow? Does open channel piping also need pumping or the increased elevation at one end will work? And how do you decide whether to use circular pipes or rectangular pipes?
Thanks,
EngReno





RE: Piping design: pipe flow v.s. open channel flow ?
Full pipe flow pretty much requires a pump (although downflow in a vertical pipe will rarely be full-pipe flow). In the event that open-channel flow is directed to a sump to pump to a higher elevation, the pump and it's discharge pipe must operate in full-pipe flow.
How often do you see rectangular pipes? There are oval culverts and other concrete "pipes", and "square" trench that is poured concrete, but I have never seen rectangular pipe. It would be enormously difficult to fit, support, transport, etc.
RE: Piping design: pipe flow v.s. open channel flow ?
It's difficult to let sail a ship in a pipe
RE: Piping design: pipe flow v.s. open channel flow ?
cheute79, what about collecting low velocity stream from scattered points and transport it to a sink. The liquid is volatile, so even for free surface flow the channel (i.e.pipe) has to be completely sealed. In this case, the only chance for air to escape is at the end of the pipe when the stream drops to the sink. Like you said, pumps are only needed if the stream collected in the sink has to be elevated afterward. However, what makes free surface flow better than pipe flow in this case? On the one hand, free surface is only driven by gravity, so there is avoided operation cost (electricity for running the pumps) Are there other pros and cons?
RE: Piping design: pipe flow v.s. open channel flow ?
Perhaps related, look up air-lift pumps and figure out how and why they operate, and what their limitations are.