1. Fluid dynamics VS frictional loss.
I once was trying to explain friction losses. My example was saying if you have a water hose with pressure on one end and the hose was long enough, nothing would come out the other.
He said "Some must come out." So I said " imagine a level hose going around the world, would you expect any water to come out the other end then?"
Sometimes exaggeration is the only way to drive a point home.
Chevy: good example, especially as touchy pneumatics are about even tiny deviations in pressure.

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Originally Posted by hvacker
Fluid dynamics VS frictional loss.
I once was trying to explain friction losses. My example was saying if you have a water hose with pressure on one end and the hose was long enough, nothing would come out the other.
He said "Some must come out." So I said " imagine a level hose going around the world, would you expect any water to come out the other end then?"
Sometimes exaggeration is the only way to drive a point home.
Chevy: good example, especially as touchy pneumatics are about even tiny deviations in pressure.
I think you're wrong about the water hose analogy (as far as stopping flow completely); friction loss would reduce the flow substantially, yes, but if you were to graph it out, it would be hyperbolic, moving infinitely closer to, but never touching, the "zero flow" line.

You could, however, achieve zero flow if the hose were run vertically and the height difference caused a pressure loss equal to or greater than the supply pressure at the water source, but that's not friction loss. :grin:

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3. I'm sure you know another use of the word hyperbola is an exaggeration of the truth.

From just the measuring of friction loss in a system we can predict fluid behavior. An assumption could be made that the losses continue until ya just run outa gas.
We seem to disagree on something nether can prove as I can't find a hose long enough.

We know that with a given pump head there are limits to how long pipe runs can be to overcome friction before the pump quits.

Longest run + 50% * constant 0.04 = required pump head.
100' + 50% = 150' * 0.04 = 6' head.
So in my head ( the other head) I sill think the water will stop running.

Limitations are part of everything we do. If my car goes 100mph on 100 hp and I want to go 200mph I'll need to increase my HP on average times 8.
Like our pump, it won't make it w/o more power.

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Originally Posted by hvacker
I'm sure you know another use of the word hyperbola is an exaggeration of the truth.
From just the measuring of friction loss in systems we can predict fluid behavior. An assumption could be made that the losses continue until ya just run outa gas.
We seem to disagree on something nether can prove as I can't find a hose long enough.
Hyperbole, hyperbola; what's the difference?

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5. Don't ask me, my degree is in Bovine Scatology.

6. If you had a hose going around the world, then yes, given enough time, water would come out the other end. Providing all else equal.

Originally Posted by hvacker
Fluid dynamics VS frictional loss.
I once was trying to explain friction losses. My example was saying if you have a water hose with pressure on one end and the hose was long enough, nothing would come out the other.
He said "Some must come out." So I said " imagine a level hose going around the world, would you expect any water to come out the other end then?"
Sometimes exaggeration is the only way to drive a point home.
Chevy: good example, especially as touchy pneumatics are about even tiny deviations in pressure.

7. Originally Posted by BBeerme
If you had a hose going around the world, then yes, given enough time, water would come out the other end. Providing all else equal.

OK Your on. Show me the science.
All else being equal is the problem as the pressure is the same and the friction is the same.
Just like pump head will only do so much on either a vertical pipe or a horizontal pipe why do you think a hose being horizontal is any different.
Water pressure is the same as pump head and will only do so much. Like my 100 hp car, I can only go so fast.

BTW, a 53 Studebaker ( the Beast)with a blown hemi just clocked 275 mph at El Mirage CA.
I know someone might say a funny car is faster. Ya, but not for long. A funny car will self destruct about 6 seconds after the green light.

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It is hard to say whether the added duct solved more of the problem or if the plenum extension did. Extending the plenum indicates the engineer thought system effect was adding too much pressure drop and reduced the system effect (pressure drop) by extending the plenum. Dual feed loops are not all that uncommon in commercial installations and are used in large chilled water and air systems to reduce fan or pump horsepower. Another advantage especially in water systems is that properly designed back feeding the coils is possible when part of the system needs to be shut down for repairs.

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The hose going around the world depends on water volume Vs pipe or hose size. Friction loss drops out if the pipe is big enough because water seeks it's own level which is the science behind it. When a river receives a lot of water from rain it develops a hump which the laws of physics tells us it cannot not hold in one place. The hump develops it's own head because the water insists on being level. As a result the hump trying to level out helps accelerate water flow. If you pump water into the pipe you have developed enough head to create the hump which will level out. Assuming the water doesn't evaporate it will eventually come out the other end because friction loss gives way to the water seeking to be level. I don't know how many years it would take.

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Water friction loss in pumped mains is calculated assuming the entire hydraulic radius of the pipe is wetted. In the example of the level pipe going around the world this will not happen so friction loss calculations are out the window.

11. Originally Posted by WAYNE3298
Water friction loss in pumped mains is calculated assuming the entire hydraulic radius of the pipe is wetted. In the example of the level pipe going around the world this will not happen so friction loss calculations are out the window.

Don't you think friction losses would apply until the pump runs out of head like in horizontal applications?. Seems the water would begin to level and any pressure would be lost. I'm applying what happens in a horizontal pipe loop. Friction still needs accounting for. Even a trickle has resistance Que'No?!
I'm sill looking for a hose.

About the duct: The plenum extension was only enough to accommodate the new duct for the doughnut. I thought the reverse thinking was clever. Like if Mohamed won't come to the mountain, bring the mountain to Mohamed.
Some people do this reversal almost automatically when confronting a problem. It's uncommon. There was often a saying in meetings to "Think out side the box". This can be said forever but still won't get many results. It's called creativity and is rare even though the solution is often obvious.
I like surprises.

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Friction head can only exist as long as water is moving thru the pipe. Friction head cannot stop all water flow because the velocity would be zero resulting in zero friction head. Vertical static head can stop all flow but friction head can't.

13. There we go, that's how you say it. As I mentioned elsewhere, I intuitively knew that a hose around the world would not create so much friction loss as to create no flow.

I was going to hit it with a simple empirical example, but this is of course the better way to say it.

Originally Posted by WAYNE3298
Friction head can only exist as long as water is moving thru the pipe. Friction head cannot stop all water flow because the velocity would be zero resulting in zero friction head. Vertical static head can stop all flow but friction head can't.

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