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Originally Posted by Canadian Man
So you guys are trying to tell me that if you add 1000x more water in a pipe that extra water weight won't add to the back pressure on the pump?
I understand your point stephane. I do think that at some point it would add more weight to the situation.
Maybe I'm a loonie  |
pressure is determined by the hight of a water column and nothing else. for an example lets say we have a tank that is 24" tall and 5" wide and 5" long that is full of water. to make up a number lets pick that the pressure on the bottom glass is 2psi. the volume of water is ~9L so the weight of water is approximately 21lbs. now take another tank, say 24 tall x 25 wide and 65 long. the volume is 590L and the weight of this tank will be ~1300 lbs, but the PSI on the bottom of the tank will still be 2psi.
the reason increasing the pipe size reduced head is because it reduces the amount of water subjected to shear. because water is composed of molecules that want to stay together when water moves it shears away from the water around it. also water will try to stay to the side of a vessel by a atomic attraction. so to get the water in the pipe to move you have to shear it apart from the water against the edge of the pipe which results in friction. by increasing the diameter of the pipe you are allowing a larger volume of water to exist away from the shear zone while will allow a greater volume to flow while not being in a state of shear and thus lowering the friction inside the pipe.
Steve
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