I am sizing a pump to transfer water from a river to a reservoir, attached is a scratch of the system. My costumer demands that the lines should be made of high density polyethylene (HDPE). I am sizing the pump discharge line to have a velocity of about 1,7 m/s, to minimize head loss due to friction. Although the elevation difference between the pump discharge and the final destiny (water reservoir) is just 15 m, there is a hill in between then where the maximum elevation of 25 m is achieved. Normally, to size the pump head required, I would calculate the head loss due to friction plus the elevation difference.
I have the some doubts and hope you could clarify the following points:
1) At steady state operation, with the line filled with liquid, the governing elevation difference is de 15m, correct?
2) But, when the line is empty (during the startup) the pump will have to fill up the line, and, in this case, the pump head required could be greater than the first case and should the selected head, correct?
3) Every time the pump will be turned down, the siphon effect would drain almost completely the pump discharge line, isn’t it? So, when the pump restarts, it would have to fill up the line again. This should be avoided? If yes, what are the options?
Hope you could help me.
Rubensvm