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Hydro in the Gutters | 67 comments (67 topical, editorial)

Re: Hydro in the Gutters (3.00 / 0) (#30)
by MattM on Sat Jun 14th, 2008 at 04:01:29 PM MST
(User Info)

The energy did not go anywhere, joe, you're intermixing "energy" with "power".

Horsepower is a unit of power, not energy. Pound-force per foot is the relative unit of energy.
----------------------------- Go Huskers!
[ Parent ]

Re: Hydro in the Gutters (3.00 / 0) (#31)
by joestue on Sat Jun 14th, 2008 at 06:12:09 PM MST
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Please try to piss me off, it's not going to work.

I am not mixing up energy and power

energy is mgh
power is mgh/seconds

one thousand kilograms of water falling 100 meters is 980,000 joules.

I don't care how long it takes to fall.

you can figure the math out.

100 feet = (32.17 feet/seconds²)t²/2

(32.17 feet/seconds²)t² = 200 feet
t² = 200 feet / 32.17 feet/seconds²
t² = 6.116208 seconds²
t = 2.47309683 seconds

100. feet / 2.47309683 seconds = 40.435133 feet / second [average speed!]
17. 333 pounds / second * 40.435133 feet / second = 700 foot-pounds per second, which is also 1.27 horsepower.

If the energy didn't go anywhere, then it should work backwards.

700 foot pounds/second will lift 7 pounds of water 100 feet per second.

you started with 17.33 pounds per second.

KISS 17.33 pound/second x 100 feet. = 1733 foot pounds per second or 3.15 horse power.

[ Parent ]

Re: Hydro in the Gutters (3.00 / 0) (#32)
by MattM on Sun Jun 15th, 2008 at 12:36:03 AM MST
(User Info)

But when you fall its not at just one static velocity. Your height displacement affects the overall velocity, which then makes the time nonlinear relative to the displacement. If the velocity is constant your formula works. Once you add in the acceleration due to gravity things are not so cut and dry.

Piss you off? Please. If pointing out the facts piss you off then so be it.
----------------------------- Go Huskers!
[ Parent ]

Re: Hydro in the Gutters (3.00 / 0) (#33)
by rossw on Sun Jun 15th, 2008 at 01:58:23 AM MST
(User Info) http://house.albury.net.au/

I think "someone" has a fundamental oopsee in thinking.

We're not dropping a given mass of water 100 feet.

We've got a continuous column of water, 100 feet high.

The PRESSURE at the bottom of a 100' column of water, times the flow, not the kinetic energy of a unit of water dropped 100' and being allowed to accelerate.

Yes, I started out tongue-in-cheek, just like the OP.

[ Parent ]

Re: Hydro in the Gutters (3.00 / 0) (#36)
by joestue on Sun Jun 15th, 2008 at 02:11:53 AM MST
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I was using kinetic energy as a way of explaining it, but you are absolutely right

[ Parent ]

Re: Hydro in the Gutters (3.00 / 0) (#47)
by MattM on Sun Jun 15th, 2008 at 06:28:03 PM MST
(User Info)

That would make sense if your home could support 62400 pounds of water on a rooftop. Otherwise you better be draining off at the same rate the water is collecting. If you are draining at the same rate you are collecting then your water is in freefall. Once your restrict the flow until its backed up all the way down that 100' drop then you now lose energy from the pressure of going through a pipe. Now you just added in atmospheric pressure into the equation. This is all going to get a lot more complicated then a simple 100' drop.
----------------------------- Go Huskers!
[ Parent ]

Re: Hydro in the Gutters (3.00 / 0) (#35)
by joestue on Sun Jun 15th, 2008 at 02:08:08 AM MST
(User Info)

Velocity does not matter.

Furthermore, you calculated average velocity, a worthless number, the RMS velocity would be a better number.

force x distance/time = power.
mass x gravitational acceleration x distance[height] / time = power

state your math

[ Parent ]

Re: Hydro in the Gutters (3.00 / 0) (#43)
by thirteen on Sun Jun 15th, 2008 at 08:37:52 AM MST
(User Info)

where does the pipe restriction work into this varying water supply problem?

[ Parent ]

Hydro in the Gutters | 67 comments (67 topical, 0 editorial)

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