Selection of pump head
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Assume that the pressure in the sealed water tank is one atmosphere. . . . The pump is used as a circulation pump; pipeline losses are not considered, nor are height differences. . . . Does the pump need to have a head greater than 1 atmosphere in order to pump water into the tank? . . So the pump’s head needs to be greater than 10 meters? ? ? Right?
It’s not understood in the way you think; there is pressure inside the tank, and there is also pressure at the inlet of the pump. Piping losses are not taken into account, height differences are not taken into account – none of these are considered? Where is the pressure difference? Without a pressure difference, the liquid will not flow.
Well, yes, the inlet pressure must be higher than the pressure inside the tank
Don’t centrifugal pumps generate head pressure? ?
That mainly involves overcoming pipeline losses and height differences. The pressure inside the tank also acts on the pump inlet.
Well, yes. The inlet pressure of the pump is the pressure inside the tank. What I’m trying to say is that the outlet pressure of the pump must be higher than the pressure inside the tank in order to pump water back into the tank, right?
Your assumption is meaningless. If pipeline losses and height differences are ignored, then no pump is needed; fluid will flow as long as the pipes are connected. This has nothing to do with the pump’s head; to find out how to calculate the pump head, check a textbook on chemical engineering principles. The pump head is the pressure at the end device minus the pressure at the inlet device, minus the pipe losses, minus the height difference. Since the pressure at the end and at the inlet is the same in your case, and both pipe losses and height difference are ignored, then what’s the need for a pump?
As you said, the output power of the pump is sufficient to overcome the pipeline resistance and height difference in order to enable circulation
What he means is not that it shouldn’t be taken into account, but rather that it shouldn’t be considered; you can treat it as a fixed value to be added at the end