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Renewable Energy Questions/Discussion => Renewable Energy Q&A => Topic started by: madlabs on January 19, 2012, 10:13:50 am
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Hi all,
So, at my neighbors place (which will be off grid) the have their well about 20-30' above their building site. For the sake of this discussion, let's say 20'. That would make 8.6 psi pressure at the build site. So, if we took a large diameter pipe, say 4", ran it down the hill to the build site and then choked it off to a smaller diameter, say 3/4", there would be an increase in pressure, no?
I have been looking around for a calculator to figger this out, but no luck. I'm guessing that it's out there and I am not searching for the right term.
Thanks!
Jonathan
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If it was gravity flow than I would say no but I may be thinking incorrect.
Ryan
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Bigger tube means more flow.
Pressure is essentially the "column" of water above the outlet and effectively the same, regardless of the outlet size. Oversimplified but that is how it works.
Sorry to blow your idea out of the water [pun intended], but that is my understanding of it.
Tom
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It's the weight of the water that creates the pressure you feel.
The weight of the water in 20' of 4" vertical pipe is more than the weight of water in a 20' @ 1 inch pipe.......
But we measure pressure as a per unit area amount..... so even for the 4" example, we take only 1 square inch of surface area at the bottom and look at that column of water only.... all the other square inches of cross section are the same........
So the diameter of the pipe counts for nil.... it is the height of the water that determines the pressure in ....lbs PER square inch...... more square inches gives you more lbs, but the same lbs/square inch..... which is your pressure.
Clear as mud..............oztules
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Drats! But part of me still thinks why isn't it like when you put your thumb over the end of a hose, you trade some volume for some pressure. Don't folks decrease pipe size in micro hydro to increase velocity?
Thanks, and forgive my ignorance!
Jonathan
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Drats! But part of me still thinks why isn't it like when you put your thumb over the end of a hose, you trade some volume for some pressure. Don't folks decrease pipe size in micro hydro to increase velocity?
Thanks, and forgive my ignorance!
Jonathan
Don't confuse velocity with pressure.
It is like amps and volts. Lots of volts [pressure] is not much without some pressure [amps]
I usually explain electriocal power using water but it works the other way, too, I guess.
Tom
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Tom, shouldn't you first "pressure" read volume instead.
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Tom, shouldn't you first "pressure" read volume instead.
Actually, I think the second one should be "volume".
Voltage is like "pressure", Amps are like "volume" or "flow".
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"Drats! But part of me still thinks why isn't it like when you put your thumb over the end of a hose, you trade some volume for some pressure. "
You need to look at what is really happening. Without the thumb over the output orifice, there is no back pressure in the hose. All the water pouring out the actual end is no longer under any pressure... as there is no restriction here (there is in the hose itself from wall friction etc).... so the water falls out, pushed only by the water behind it trying to get out too.
When you restrict it, you build up back pressure. If you block it off you will build up full pressure.
So if we had a pressure gauge tapped into the hose say 1 foot in from the outlet, with no thumb, we get very low pressure, but max volume, but when we clamp the end of the hose, we get the static high pressure, and no volume..... so we can use anywhere in between those two states to do things.
If we partly open the outlet (spray a bit about) the pressure now in the hose tries to push whatever volume of water it can, out through the smaller orifice. It cannot push with more pressure than the static pressure (blocked hose).... and will always be less once we release water out.
Friction losses in the hose (result of velocity of the water and hose diameter ) work against us too.
So the smaller the outlet hole, the greater the pressure can build towards static max..... and the more pressure available to push the max water out of the hole.... so it moves faster.
But the pressure can never be higher than the static pressure (except for inertial change... ie the instant you block it..... you must decelerate the water that was moving. This can be used for ram pumping to very high pressure.).
Nothing is for nothing in this universe.... so for turbines we use jets to get the best combination of water velocity driven by back pressure. Restrict too much and we get high back pressure..... but we lose the mass.
If we don't restrict enough, we lose the velocity needed to turn the turbine fast enough.... but you cant beat the turned off (static) pressure. You can balance the pressure:velocity part to get what you need, but not pressure max.... the more you open the jet, the less pressure built up in the pipe to push the water out with.
just more mud....................oztules
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Tom, shouldn't you first "pressure" read volume instead.
Actually, I think the second one should be "volume".
Voltage is like "pressure", Amps are like "volume" or "flow".
Damn, I had a 50/50 chance, I knew one of em should be volume.
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Wow, I always thought of it as voltage = flow speed, amperage= pressure, volume= storage capacity ( in watt hours)
Correct me in how I am wrong
My reasoning,
Voltage/ Flow Either can be very fast but if there is no pressure there can be very little work done.
Amperage/ Pressure If you have to much amperage, it will burn/damage its vessel. as such pressure will do the same
Volume /KWh = Think of it as storage capacity.
Watts = I cannot think of the term for a water equivalent without referring back to a measure of energy such as joules.. However it directly relates as water speed times pressure= work capacity at any given time of measurement.
Ok so thats just how I have always understood it
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Wow, I always thought of it as voltage = flow speed, amperage= pressure, volume= storage capacity ( in watt hours)
Correct me in how I am wrong
My reasoning,
Voltage/ Flow Either can be very fast but if there is no pressure there can be very little work done.
Amperage/ Pressure If you have to much amperage, it will burn/damage its vessel. as such pressure will do the same
Volume /KWh = Think of it as storage capacity.
Watts = I cannot think of the term for a water equivalent without referring back to a measure of energy such as joules.. However it directly relates as water speed times pressure= work capacity at any given time of measurement.
Ok so thats just how I have always understood it
I think of "amperage" as being like "flow", because you need a large wire to carry a lot of amps, just like you need a large pipe to carry a lot of water (flow). Wire insulation needs to be thicker for higher voltage (pressure) just like pipe wall thickness has to be thicker for higher pressures.
A high pressure (voltage) CAN cause a high flow (current) as long as your pipes/wires are big enough
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Lemmeesee....
If we take voltage, we can see that it pushes the electrons through a circuit.
If we take pressure, we use it to push the water molecules through the water circuit (hose, pipe etc)
So pressure is volts..... psi
Flow rate is the current .... number of electrons or water molecules flowing at the moment.
So Amps is flow rate .... gallon per minute, cubic feet/second. etc
If we get the flow rate and divide by time we get volume..... If a coulomb /sec is an amp, then a gallon per second/second is a volume.
So a coulomb is Volume .... gallons or cubic feet etc.
Now :D
So watts are pressure X flow rate..or psi X gpm
Watt hours are psi X gpm X hours
even more mud................oztules
anyone want to try capacitance?? perhaps area x head :-\
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"even more mud................oztules
anyone want to try capacitance?? perhaps area x head "
Well, in the hose and pressure discussion, the hose as it expands when the big digit is over the end, act sort of like a capacitor storing energy. Partially removing the big digit must be similar to a variable resistor.
Just stirring the mud .....
Ron
BTW, this has been a good discussion. It clarified how I can describe sparky stuff to the ignorant.
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"BTW, this has been a good discussion. It clarified how I can describe sparky stuff to the ignorant"
Just use a tazer and take questions afterwards. :)
Rover
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Oz, perfect explanation. Made me go DUH, which, for me anyway, is always the sign of a good explanation.
Thanks!
Jonathan
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Well I think this thread should be preserved at the top of the list some how ,just so it doesn't get lost in the shuffel. Excellent thread ,maybe add to the title though to mention the electrical part. Gotta go back and reread this a few more times............thanks ...........artv
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I agree, this is an excellent discussion. I have taught basic electricity for 20 years. To recap, voltage = pressure, amperage = rate of flow, wattage (power) = flow x pressure and energy = flow x pressure x time. Someone mentioned capacitance. Think of a water tank. Capacitance = volume of tank. Pressure is directly related to height of tank. Chuck
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Hi all, been reading and experimenting,
If you put a stick ,down into a flowing stream, the stream will swirl around the stick.?..right?
If you can get these swirls to act together ,...you can increase out-put......
You need a form of controlled switching( I need )
artv
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You need a different hobby art.
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To get back to the original question.....
So, if we took a large diameter pipe, say 4", ran it down the hill to the build site and then choked it off to a smaller diameter, say 3/4", there would be an increase in pressure, no?
Bluntly no....
If you had a garden hose with a nozzle at the bottom of the hill ....turned it on
so it was really squirting out hard enough to knock your socks off ......
aimed it toward the sky....it could do no more than squirt as high as the top of
the 20 ft. hill ....if you walked up the hill 10 ft. to try and squirt Billy Bob at the
top of the hill with the hose ? ....nuff said ::)
Norm :D
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Having studied hydraulics, water flow and pressure is a hydraulic situation. Pumps create flow and pipes create pressure. This is why homes are Piped 3/4 inch all the way to the area we want to plumb then reduce to 1/2 inch stubbed thru the wall and finally 3/8 to the fixtures .
Reducing down creates the necessary pressure needed at the fixture but larger piping to the general area will allow a high volume of water. Reduction in piping also prevents being roasted by hot water in the shower when someone flushes the toilet that got plumbed with 1/2 inch pipe. American mobile home manufacturers do this commonly (idiot syndrome to save pennies).
As for the well being 20 ft above the home, you would get that extra column of pressure created by gravity if you drilled straight down 20 ft then straight over to house, you may gain 20psi but since your coming down at an angle the column is not affected by gravity the same as a vertical column. I'm sure there's more math involved to find the advantage going down hill from the well. 1" or 4" you'll get the same results when they tie to the 3/4" piping at the house. Better off just running 1" right off the pump unless it's a submersed pump (1 1/4 to 2")then your dealing with head pressure and the pumps capability of pumping against gravity. I have heard that for solar purposes submersibles are a better alternative. They run off 220v and can keep up with those long showers.
For every foot of water column you achieve 1 psi, hence the popularity of water towers. Pumps keep the tank full much easier than pumps trying to keep up with varying customer demand.
Well, hope that clarifies it. Oz make my eyes crossed tho
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"For every foot of water column you achieve 1 psi,".... hmm not really.
Water only has Specific Gravity of 1.... so actually 1 foot of ( fresh) water equates to about .43psi..... so 20 ft of head from our original hill is 8.6 psi etc etc etc.
If we wanted to pretend that 1 ft of water = 1psi, .... then the waters specific gravity would need to be in the region of 2.3
.................oztules
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you would get that extra column of pressure created by gravity if you drilled straight down 20 ft then straight over to house, you may gain 20psi but since your coming down at an angle the column is not affected by gravity the same as a vertical column.
I think you're dead set wrong there.
The static pressure is a function of the total vertical difference. 20 feet straight down is the same pressure as 20 feet down and 20 feet sideways (ie, 28 feet at 45 degrees).
BUT pressure under flow is reduced by the friction losses, and here the friction losses over 20 feet horizontally at full pressure would be higher than the friction losses of a total of 28 feet of the same pipe, at a 45 degree angle - meaning the angled pipe will deliver more pressure at a given flow rate, than 20 feet down then 20 feet across!
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If it was gravity flow than I would say no but I may be thinking incorrect.
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Old thread I know but was wondering if they were using a submersible Pump or shallow well and what size discharge pipe.
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Damn, I had a 50/50 chance, I knew one of em should be volume. :)
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