f



TOTALLY OT: Pumping water with an elevated pump.

Hey, smart people.

I've been having a discussion with a firefighter that's gone something
like this (heavily paraphrased):

He:  You know you can only lift water about 28ft with a pump?  It's
physically impossible to pump it higher than that if the pump is at
the top of the lift.

(e.g., a pump at the top of a well, something like that)

Me:  I think that's only a limit for a vacuum pump.   Doesn't it work
if you prime the pump from the top?

He:  I repeat, it's physically impossible to pump water higher than
30ft with an elevated pump.

I made this diagram to try to describe what I was thinking, since he
wasn't understanding my explanation:

http://www.ericjacobsen.org/pics/Pumpsnstuff.jpg

The pertinent stuff is Example 3, where Case A is the limit imposed by
trying to lift water with a vacuum pump.   The pressure differential
between 1 Atm and a complete vacuum created behind the pump is the
limitation, so I suggested Case B and Case C, where a prime tank with
enough volume to fill the pipe and the pump is used to prime the
system, so that the pressure differential is no longer limiting the
ability to lift the water.

So far the response is simply, "That won't work."

Apparently common firefighter training conveys that this is
impossible, but I'm failing to see why.   I've found little on the
internet with the searches I've tried, with the exception of how trees
pump water as high as, apparently, 450m under tension (which is pretty
cool, btw).

Does anybody know of an example of this sort of thing working or a
reason why it wouldn't?



Eric Jacobsen
Minister of Algorithms
Abineau Communications
http://www.ericjacobsen.org
0
eric.jacobsen (2636)
11/20/2007 9:43:28 PM
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Eric Jacobsen wrote:
> Hey, smart people.
> 
> I've been having a discussion with a firefighter that's gone something
> like this (heavily paraphrased):
> 
> He:  You know you can only lift water about 28ft with a pump?  It's
> physically impossible to pump it higher than that if the pump is at
> the top of the lift.
> 
> (e.g., a pump at the top of a well, something like that)
> 
> Me:  I think that's only a limit for a vacuum pump.   Doesn't it work
> if you prime the pump from the top?
> 
> He:  I repeat, it's physically impossible to pump water higher than
> 30ft with an elevated pump.

Elevated above what?

> I made this diagram to try to describe what I was thinking, since he
> wasn't understanding my explanation:
> 
> http://www.ericjacobsen.org/pics/Pumpsnstuff.jpg
> 
> The pertinent stuff is Example 3, where Case A is the limit imposed by
> trying to lift water with a vacuum pump.

The proper terminology is "suction pump". A vacuum pump is used to 
create a vacuum, as in semiconductor fabrication.

>                                        The pressure differential
> between 1 Atm and a complete vacuum created behind the pump is the
> limitation, so I suggested Case B and Case C, where a prime tank with
> enough volume to fill the pipe and the pump is used to prime the
> system, so that the pressure differential is no longer limiting the
> ability to lift the water.
> 
> So far the response is simply, "That won't work."

He's right. The pressure at the free surface of the sump (and in the 
pipe at the same elevation) is atmospheric, say 15 psia. It drops 
linearly with elevation to zero at 34 feet, (ignoring that it will boil 
at much over 32 feet), and becomes negative after that. A column of 
water sustains very little tension.

> Apparently common firefighter training conveys that this is
> impossible, but I'm failing to see why.   I've found little on the
> internet with the searches I've tried, with the exception of how trees
> pump water as high as, apparently, 450m under tension (which is pretty
> cool, btw).

Under capillary conditions, yes. in a pipe, no.

> Does anybody know of an example of this sort of thing working or a
> reason why it wouldn't?

Go back to Case C of example 3. Mark off the 32 feet as in Case A and 
continue the scale up to the pump. What is the inlet pressure at the 
pump? Is that physically realizable? What is the vapor pressure of water 
at room temperature? (Water boils when its vapor pressure exceeds the 
external pressure.)

Jerry
-- 
Engineering is the art of making what you want from things you can get.
�����������������������������������������������������������������������
0
jya (12871)
11/20/2007 10:32:31 PM
On Tue, 20 Nov 2007 17:32:31 -0500, Jerry Avins <jya@ieee.org> wrote:

>Eric Jacobsen wrote:
>> Hey, smart people.
>> 
>> I've been having a discussion with a firefighter that's gone something
>> like this (heavily paraphrased):
>> 
>> He:  You know you can only lift water about 28ft with a pump?  It's
>> physically impossible to pump it higher than that if the pump is at
>> the top of the lift.
>> 
>> (e.g., a pump at the top of a well, something like that)
>> 
>> Me:  I think that's only a limit for a vacuum pump.   Doesn't it work
>> if you prime the pump from the top?
>> 
>> He:  I repeat, it's physically impossible to pump water higher than
>> 30ft with an elevated pump.
>
>Elevated above what?
>
>> I made this diagram to try to describe what I was thinking, since he
>> wasn't understanding my explanation:
>> 
>> http://www.ericjacobsen.org/pics/Pumpsnstuff.jpg
>> 
>> The pertinent stuff is Example 3, where Case A is the limit imposed by
>> trying to lift water with a vacuum pump.
>
>The proper terminology is "suction pump". A vacuum pump is used to 
>create a vacuum, as in semiconductor fabrication.
>
>>                                        The pressure differential
>> between 1 Atm and a complete vacuum created behind the pump is the
>> limitation, so I suggested Case B and Case C, where a prime tank with
>> enough volume to fill the pipe and the pump is used to prime the
>> system, so that the pressure differential is no longer limiting the
>> ability to lift the water.
>> 
>> So far the response is simply, "That won't work."
>
>He's right. The pressure at the free surface of the sump (and in the 
>pipe at the same elevation) is atmospheric, say 15 psia. It drops 
>linearly with elevation to zero at 34 feet, (ignoring that it will boil 
>at much over 32 feet), and becomes negative after that. A column of 
>water sustains very little tension.
>
>> Apparently common firefighter training conveys that this is
>> impossible, but I'm failing to see why.   I've found little on the
>> internet with the searches I've tried, with the exception of how trees
>> pump water as high as, apparently, 450m under tension (which is pretty
>> cool, btw).
>
>Under capillary conditions, yes. in a pipe, no.
>
>> Does anybody know of an example of this sort of thing working or a
>> reason why it wouldn't?
>
>Go back to Case C of example 3. Mark off the 32 feet as in Case A and 
>continue the scale up to the pump. What is the inlet pressure at the 
>pump? Is that physically realizable? What is the vapor pressure of water 
>at room temperature? (Water boils when its vapor pressure exceeds the 
>external pressure.)
>
>Jerry

Jerry, thanks.   I came to the same conclusion with a little more
searching, and although I couldn't find a reference that said 'it
boils', I'd concluded that that was basically what would happen.   I'm
glad you've confirmed that for me.

FWIW, I did, in my searching, find a reference from 1969 where a guy
in the UK sorted out that if you eliminate cavitation nuclei and do a
few other things, like de-aerate the prime water, you can 'suction'
water to 17m.   This was a paper in Nature in 1970, so the credibility
is pretty high.   He claimed to be working on improvements, but I
didn't find anything subsequent.

I also found some other confusing things:  As you mention there are
claims that one 'can't pull water, only push it' because water has no
tensile strength, and other sources that claim liquids in certain
conditions have very high tensile strengths...which is what the guy
who did the 17m lift was exploiting.

Regardless, for the majority of applications the ~30 ft limit appears
to be real enough.  At least now I understand why.

Eric Jacobsen
Minister of Algorithms
Abineau Communications
http://www.ericjacobsen.org
0
eric.jacobsen (2636)
11/20/2007 10:44:17 PM
Hi Eric,
A 'vacuum' is the lowest pressure that you can create in a pipe if you 
are pumping air, but with a liquid the position is entirely different as 
a column of liquid has a tensile strength.  A suitable pump can actually 
'pull' the liquid, creating a negative pressure.

The 28 ft. limitation comes in with water because water will boil at 
room temperature when a near-vacuum is applied. This means that the 
column of water breaks up into bubbles and the liquid component 
collapses to the bottom of the pipe.

In theory it should be possible to pull an oil column much higher, even 
allowing for its lower density relative to water.  Because of its lower 
vapuur-pressure, oil will not boil under a vacuum at room temperature. 
In photos of oil-wells they often seem to be pumping from the top, but 
that is as close as I have ever been so I can't say for sure.

The case you mention of tree transpiration is an interesting one, as the 
water is actually pulled up by the leaves.   I am not sure that this has 
been completely analysed.  The fact that the water is in very fine tubes 
in the tissue of the tree must have something to do with it, together 
with the adhesion of the water to the tube wall.



Regards,
John



Eric Jacobsen wrote:
> Hey, smart people.
> 
> I've been having a discussion with a firefighter that's gone something
> like this (heavily paraphrased):
> 
> He:  You know you can only lift water about 28ft with a pump?  It's
> physically impossible to pump it higher than that if the pump is at
> the top of the lift.
> 
> (e.g., a pump at the top of a well, something like that)
> 
> Me:  I think that's only a limit for a vacuum pump.   Doesn't it work
> if you prime the pump from the top?
> 
> He:  I repeat, it's physically impossible to pump water higher than
> 30ft with an elevated pump.
> 
> I made this diagram to try to describe what I was thinking, since he
> wasn't understanding my explanation:
> 
> http://www.ericjacobsen.org/pics/Pumpsnstuff.jpg
> 
> The pertinent stuff is Example 3, where Case A is the limit imposed by
> trying to lift water with a vacuum pump.   The pressure differential
> between 1 Atm and a complete vacuum created behind the pump is the
> limitation, so I suggested Case B and Case C, where a prime tank with
> enough volume to fill the pipe and the pump is used to prime the
> system, so that the pressure differential is no longer limiting the
> ability to lift the water.
> 
> So far the response is simply, "That won't work."
> 
> Apparently common firefighter training conveys that this is
> impossible, but I'm failing to see why.   I've found little on the
> internet with the searches I've tried, with the exception of how trees
> pump water as high as, apparently, 450m under tension (which is pretty
> cool, btw).
> 
> Does anybody know of an example of this sort of thing working or a
> reason why it wouldn't?
> 
> 
> 
> Eric Jacobsen
> Minister of Algorithms
> Abineau Communications
> http://www.ericjacobsen.org
0
11/20/2007 10:44:45 PM
John Monro wrote:

> A 'vacuum' is the lowest pressure that you can create in a pipe if you 
> are pumping air, but with a liquid the position is entirely different as 
> a column of liquid has a tensile strength.  A suitable pump can actually 
> 'pull' the liquid, creating a negative pressure.

> The 28 ft. limitation comes in with water because water will boil at 
> room temperature when a near-vacuum is applied. This means that the 
> column of water breaks up into bubbles and the liquid component 
> collapses to the bottom of the pipe.

> In theory it should be possible to pull an oil column much higher, even 
> allowing for its lower density relative to water.  Because of its lower 
> vapuur-pressure, oil will not boil under a vacuum at room temperature. 
> In photos of oil-wells they often seem to be pumping from the top, but 
> that is as close as I have ever been so I can't say for sure.

That is if there are no low boiling point (high vapor pressure)
hydrocarbons (or others) in the oil.

I always thought the oil well pumps pulled a cable that went down
to the bottom of the well where the actual pump was.

-- glen

0
gah (12851)
11/20/2007 11:24:03 PM
Jerry Avins wrote:
> Eric Jacobsen wrote:
>> Hey, smart people.
>>
>> I've been having a discussion with a firefighter that's gone something
>> like this (heavily paraphrased):
>>
>> He:  You know you can only lift water about 28ft with a pump?  It's
>> physically impossible to pump it higher than that if the pump is at
>> the top of the lift.
>>
>> (e.g., a pump at the top of a well, something like that)
>>
>> Me:  I think that's only a limit for a vacuum pump.   Doesn't it work
>> if you prime the pump from the top?
>>
>> He:  I repeat, it's physically impossible to pump water higher than
>> 30ft with an elevated pump.
> 
> Elevated above what?
> 
>> I made this diagram to try to describe what I was thinking, since he
>> wasn't understanding my explanation:
>>
>> http://www.ericjacobsen.org/pics/Pumpsnstuff.jpg
>>
>> The pertinent stuff is Example 3, where Case A is the limit imposed by
>> trying to lift water with a vacuum pump.
> 
> The proper terminology is "suction pump". A vacuum pump is used to 
> create a vacuum, as in semiconductor fabrication.
> 
>>                                        The pressure differential
>> between 1 Atm and a complete vacuum created behind the pump is the
>> limitation, so I suggested Case B and Case C, where a prime tank with
>> enough volume to fill the pipe and the pump is used to prime the
>> system, so that the pressure differential is no longer limiting the
>> ability to lift the water.
>>
>> So far the response is simply, "That won't work."
> 
> He's right. The pressure at the free surface of the sump (and in the 
> pipe at the same elevation) is atmospheric, say 15 psia. It drops 
> linearly with elevation to zero at 34 feet, (ignoring that it will boil 
> at much over 32 feet), and becomes negative after that. A column of 
> water sustains very little tension.
> 
>> Apparently common firefighter training conveys that this is
>> impossible, but I'm failing to see why.   I've found little on the
>> internet with the searches I've tried, with the exception of how trees
>> pump water as high as, apparently, 450m under tension (which is pretty
>> cool, btw).
> 
> Under capillary conditions, yes. in a pipe, no.

There is no difference. The capillary condition is not sucking from the 
top. It is sucking in a distributed manner the whole way up. If a 
localised condition occurred in the capillary system that equated to 10m 
of sucking, things would behave like any other sucking up a pipe.
> 
>> Does anybody know of an example of this sort of thing working or a
>> reason why it wouldn't?
> 
> Go back to Case C of example 3. Mark off the 32 feet as in Case A and 
> continue the scale up to the pump. What is the inlet pressure at the 
> pump? Is that physically realizable? What is the vapor pressure of water 
> at room temperature? (Water boils when its vapor pressure exceeds the 
> external pressure.)

Jerry loves quoting sewerage treatment works. There is a good reason why 
those works build very expensive large holes in the ground, and put 
their huge inlet water pumps at the bottom.

People think politicians are a bit bit wet, but there is a difference. 
The suckage of water has its limits. :-)

Steve
0
steveu (1008)
11/21/2007 12:22:14 AM
I think the system my parents had while I were a kid was using something 
called injection pump.
Most of the water were send back into the drill hole in a second pipe, 
and only part of the lifted water were used at once.

Our well was 12m (40feet), and I cannot remember anything about any pump 
in the bottom.
There were 2 pipes in the drill hole, one for water going down.
We had to prime the system with water, if it lost water.
I guess the drill hole were air tight, but not sure (to raise pressure 
in the hole).

It has been some years ago. And me getting older, I cannot remember all 
that well ;-)

How does this sound anyway?

-- 
Christen Fihl


0
11/21/2007 12:30:43 AM
Eric Jacobsen <eric.jacobsen@ieee.org> writes:

> On Tue, 20 Nov 2007 17:32:31 -0500, Jerry Avins <jya@ieee.org> wrote:
>
>>Eric Jacobsen wrote:
>>> ......
>>>       I've found little on the
>>> internet with the searches I've tried, with the exception of how trees
>>> pump water as high as, apparently, 450m under tension (which is pretty
>>> cool, btw).

If this refers to newer work on the subject, I would be very
interested to find it too.  As this is not related to my regular work
and I am German, I have no idea of good terms to search for.  Please
could you help me?

>> ...
>>> Does anybody know of an example of this sort of thing working or a
>>> reason why it wouldn't?

An example is the traditional device for measuring preasure of air:
close a tube of glass at one end (by melting), fill it with mercury,
submerge the open end into mercury in a container, bring the tube into
vertical position.  Provided the tube is long enough, the level of the
mercury in the tube will be about 760mm above the one in the container.
In the upper end of the tube is vacuum.

>
> FWIW, I did, in my searching, find a reference from 1969 where a guy
> in the UK sorted out that if you eliminate cavitation nuclei and do a
> few other things, like de-aerate the prime water, you can 'suction'
> water to 17m.   This was a paper in Nature in 1970, so the credibility
> is pretty high.   He claimed to be working on improvements, but I
> didn't find anything subsequent.

Yes, I once also read about this.  

>
> I also found some other confusing things:  As you mention there are
> claims that one 'can't pull water, only push it' because water has no
> tensile strength, and other sources that claim liquids in certain
> conditions have very high tensile strengths...which is what the guy
> who did the 17m lift was exploiting.
>

The problem here is, what you understand under tensile strength.  Its
a macroscopic quantity which is rather easily measured for a rod of
metal.  At a microscopic (atomic) scale we see that the strength is
produced by intermolecular forces and those we also have in water as
can be seen from a drop of water on e.g. a greasy surface.  So water
also has tensile strength though it can not be measured the way it is
done for metals.

I just did a simple experiment in my kitchen which, I think,
clearly demonstrates the tensile strength of water.

I filled a class of _cold_ water up next to the rim.
(Temperature was about eight Celsius.)  Then I looked for the next
thing that might be appropriate and got hold of an eating-knive, where
the end of the handle is of metal, a little rounded, and about 8x12
millimeters in crossection.  I emerged the end of the handle a little
into the water and pulled it slowly upwards, holding the knive in
vertical position.  The water kept connected to the handle until it's
end was 2 or 3 millimeters above the surface.  So I ``pulled'' water,
which, I claim, requires ``tensile strength''.

But I won't say this is ``very high tensile strength''.  When pulling
up water by 10m, a column of one square-centimeter crossection weighs
1kg.  Hardly anybody would call a rope of half an inch diameter strong,
when it breaks under a load of a few kilograms.

-- 
hw
0
hwmuell (37)
11/21/2007 12:58:09 AM
Heinrich Wolf wrote:
> Eric Jacobsen <eric.jacobsen@ieee.org> writes:
> 
>> On Tue, 20 Nov 2007 17:32:31 -0500, Jerry Avins <jya@ieee.org> wrote:
>>
>>> Eric Jacobsen wrote:
>>>> ......
>>>>       I've found little on the
>>>> internet with the searches I've tried, with the exception of how trees
>>>> pump water as high as, apparently, 450m under tension (which is pretty
>>>> cool, btw).
> 
> If this refers to newer work on the subject, I would be very
> interested to find it too.  As this is not related to my regular work
> and I am German, I have no idea of good terms to search for.  Please
> could you help me?
> 
>>> ...
>>>> Does anybody know of an example of this sort of thing working or a
>>>> reason why it wouldn't?
> 
> An example is the traditional device for measuring preasure of air:
> close a tube of glass at one end (by melting), fill it with mercury,
> submerge the open end into mercury in a container, bring the tube into
> vertical position.  Provided the tube is long enough, the level of the
> mercury in the tube will be about 760mm above the one in the container.
> In the upper end of the tube is vacuum.
> 
>> FWIW, I did, in my searching, find a reference from 1969 where a guy
>> in the UK sorted out that if you eliminate cavitation nuclei and do a
>> few other things, like de-aerate the prime water, you can 'suction'
>> water to 17m.   This was a paper in Nature in 1970, so the credibility
>> is pretty high.   He claimed to be working on improvements, but I
>> didn't find anything subsequent.
> 
> Yes, I once also read about this.  
> 
>> I also found some other confusing things:  As you mention there are
>> claims that one 'can't pull water, only push it' because water has no
>> tensile strength, and other sources that claim liquids in certain
>> conditions have very high tensile strengths...which is what the guy
>> who did the 17m lift was exploiting.
>>
> 
> The problem here is, what you understand under tensile strength.  Its
> a macroscopic quantity which is rather easily measured for a rod of
> metal.  At a microscopic (atomic) scale we see that the strength is
> produced by intermolecular forces and those we also have in water as
> can be seen from a drop of water on e.g. a greasy surface.  So water
> also has tensile strength though it can not be measured the way it is
> done for metals.
> 
> I just did a simple experiment in my kitchen which, I think,
> clearly demonstrates the tensile strength of water.
> 
> I filled a class of _cold_ water up next to the rim.
> (Temperature was about eight Celsius.)  Then I looked for the next
> thing that might be appropriate and got hold of an eating-knive, where
> the end of the handle is of metal, a little rounded, and about 8x12
> millimeters in crossection.  I emerged the end of the handle a little
> into the water and pulled it slowly upwards, holding the knive in
> vertical position.  The water kept connected to the handle until it's
> end was 2 or 3 millimeters above the surface.  So I ``pulled'' water,
> which, I claim, requires ``tensile strength''.

You demonstrated surface tension. Search for a way to measure surface 
tension with a wire frame one centimeter wide and an analytical balance. 
The general topic id physical chemistry.

> But I won't say this is ``very high tensile strength''.  When pulling
> up water by 10m, a column of one square-centimeter crossection weighs
> 1kg.  Hardly anybody would call a rope of half an inch diameter strong,
> when it breaks under a load of a few kilograms.

It is what keeps the water in a soap bubble from flowing to the bottom. 
See http://tinyurl.com/2h3fbl for a wonderful treatise on the subject.

Jerry
-- 
Engineering is the art of making what you want from things you can get.
�����������������������������������������������������������������������
0
jya (12871)
11/21/2007 1:33:14 AM
John Monro wrote:
> In theory it should be possible to pull an oil column much higher, even 
> allowing for its lower density relative to water.  Because of its lower 
> vapour-pressure, oil will not boil under a vacuum at room temperature. 
> In photos of oil-wells they often seem to be pumping from the top, but 
> that is as close as I have ever been so I can't say for sure.

Have you ever noticed those nodding things in pictures of Texas? They 
are reaching deep down to pump up the oil from below. Deep wells use 
more sophisticated pumps popped down the holes, when natural pressure no 
longer pushes the oil out.

Steve
0
steveu (1008)
11/21/2007 2:23:52 AM
Christen Fihl wrote:
> I think the system my parents had while I were a kid was using something 
> called injection pump.
> Most of the water were send back into the drill hole in a second pipe, 
> and only part of the lifted water were used at once.
> 
> Our well was 12m (40feet), and I cannot remember anything about any pump 
> in the bottom.
> There were 2 pipes in the drill hole, one for water going down.
> We had to prime the system with water, if it lost water.
> I guess the drill hole were air tight, but not sure (to raise pressure 
> in the hole).
> 
> It has been some years ago. And me getting older, I cannot remember all 
> that well ;-)
> 
> How does this sound anyway?

You are describing a deep-well jet pump. We had one; my father had his 
fatal heart attack priming it. There is a venturi under water, and water 
pumped down (in our case) a one-inch line. The output of the venturi was 
a 1.5-inch line, pressured by the venturi and tied to the suction end of 
a centrifugal pump. I was lucky: the suction sprung a leak somewhere, 
and I replaces the venturi with a submersible pump. no digging was 
needed. The old one-inch line became the pump's delivery line, and the 
piece of old 1.5-inch delivery line, leak and all, became the conduit 
for the wire to power the pump. (I cut it off at the well head, where 
the wires are spliced.) The pump,a shallow-well above-ground jet, and a 
deep-well jet are shown at 
http://www.femyers.com/products/sse/sse_mflconvert.html

Jerry
-- 
Engineering is the art of making what you want from things you can get.
�����������������������������������������������������������������������
0
jya (12871)
11/21/2007 2:31:38 AM
As I recall, boiling can be ignored until one asks "why?" about one of the 
practicalities of it.

Eric's diagram Figure 3 Case A comes close enough.

You draw a free body diagram of a chunk of water.
Consider a chunk of water at the top of the water column.
The pressure at the bottom is 1 atm. or around 15psia.
The pressure reduces going up the water column until, at the surface the 
pressure is zero psia.

There's no such thing as negative pressure in a gas or liquid - in the gross 
sense at least.  They have no tensile strength.  The minimum pressure 
(theoretical at that - a perfect vacuum) is zero psia.

Now, back to that chunk of water free body diagram.  If the pressure on one 
side were smaller than the pressure on the other, the water would move. 
y'know: f=ma, and it could be thus "pumped".  But, the pressure on the top 
side can't be smaller than zero.  Turn things around and ask "at what height 
will the pressure be zero?"  Oh! around 32 feet. There doesn't have to be a 
void to reach this conclusion.  But, it tends to explain how a void would be 
formed through some mechanism or other if one tried to pump thereafter.

One might ask: "What happens if a piston pump "pulls" on the water after the 
pressure reaches zero psia?"  The only thing that happens is that the piston 
stops or breaks or a void is formed.  If there's a void and no more water to 
boil then the void gets larger and the vacuum becomes "better" in terms of 
the number of molecules of gas still bouncing around in there.  But it's 
still not zero psia actually.

Fred 


0
fmarshallx1 (1639)
11/21/2007 2:51:24 AM
On Wed, 21 Nov 2007 01:58:09 +0100, Heinrich Wolf
<hwmuell@willis-werkstaette.de> wrote:

>Eric Jacobsen <eric.jacobsen@ieee.org> writes:
>
>> On Tue, 20 Nov 2007 17:32:31 -0500, Jerry Avins <jya@ieee.org> wrote:
>>
>>>Eric Jacobsen wrote:
>>>> ......
>>>>       I've found little on the
>>>> internet with the searches I've tried, with the exception of how trees
>>>> pump water as high as, apparently, 450m under tension (which is pretty
>>>> cool, btw).
>
>If this refers to newer work on the subject, I would be very
>interested to find it too.  As this is not related to my regular work
>and I am German, I have no idea of good terms to search for.  Please
>could you help me?

Here are some of the interesting urls I found:

http://books.google.com/books?id=w6bUF8bOfKEC&pg=PA47&lpg=PA47&dq=pulling+water+higher&source=web&ots=UeCtrueSKC&sig=m7KXqMvDvdfVLFyyvhQPXogjz8I#PPA47,M1

which talks about tension-cohesion being able to feed trees up to
450m.   I guess that drives a practical limit on tree height?   ;)

This is the abstract for the Hayward paper, which addresses
controlling cavitation to improve suction lifting (it's a short paper,
doesn't go into detail, just explains the basics about the pump):

http://www.nature.com/nature/journal/v225/n5230/abs/225376b0.html

And I love how he cites a paper from 1850.

And this article which references Hayward's work.   Section 4.1 is
interesting, and section 7.1 also deals with feeding trees (overall a
pretty cool paper, IMHO):

http://www.lps.ens.fr/~caupin/fichiersPDF/CRPhys_2006_7_1000-1017.pdf

You can see from the first url I was searching on just simple terms
like "pulling water higher", but I got good stuff by adding "suction"
and things like that as well.


>>> ...
>>>> Does anybody know of an example of this sort of thing working or a
>>>> reason why it wouldn't?
>
>An example is the traditional device for measuring preasure of air:
>close a tube of glass at one end (by melting), fill it with mercury,
>submerge the open end into mercury in a container, bring the tube into
>vertical position.  Provided the tube is long enough, the level of the
>mercury in the tube will be about 760mm above the one in the container.
>In the upper end of the tube is vacuum.
>
>>
>> FWIW, I did, in my searching, find a reference from 1969 where a guy
>> in the UK sorted out that if you eliminate cavitation nuclei and do a
>> few other things, like de-aerate the prime water, you can 'suction'
>> water to 17m.   This was a paper in Nature in 1970, so the credibility
>> is pretty high.   He claimed to be working on improvements, but I
>> didn't find anything subsequent.
>
>Yes, I once also read about this.  
>
>>
>> I also found some other confusing things:  As you mention there are
>> claims that one 'can't pull water, only push it' because water has no
>> tensile strength, and other sources that claim liquids in certain
>> conditions have very high tensile strengths...which is what the guy
>> who did the 17m lift was exploiting.
>>
>
>The problem here is, what you understand under tensile strength.  Its
>a macroscopic quantity which is rather easily measured for a rod of
>metal.  At a microscopic (atomic) scale we see that the strength is
>produced by intermolecular forces and those we also have in water as
>can be seen from a drop of water on e.g. a greasy surface.  So water
>also has tensile strength though it can not be measured the way it is
>done for metals.
>
>I just did a simple experiment in my kitchen which, I think,
>clearly demonstrates the tensile strength of water.
>
>I filled a class of _cold_ water up next to the rim.
>(Temperature was about eight Celsius.)  Then I looked for the next
>thing that might be appropriate and got hold of an eating-knive, where
>the end of the handle is of metal, a little rounded, and about 8x12
>millimeters in crossection.  I emerged the end of the handle a little
>into the water and pulled it slowly upwards, holding the knive in
>vertical position.  The water kept connected to the handle until it's
>end was 2 or 3 millimeters above the surface.  So I ``pulled'' water,
>which, I claim, requires ``tensile strength''.
>
>But I won't say this is ``very high tensile strength''.  When pulling
>up water by 10m, a column of one square-centimeter crossection weighs
>1kg.  Hardly anybody would call a rope of half an inch diameter strong,
>when it breaks under a load of a few kilograms.

As Jerry mentioned, I think you demonstrated surface tension, which is
a bit different than material tensile strength.   Nevertheless, some
of the references hint that tensile strength does come into play with
some of these pumping or "negative pressure" effects.

Pretty interesting stuff, in any case.
Eric Jacobsen
Minister of Algorithms
Abineau Communications
http://www.ericjacobsen.org
0
eric.jacobsen (2636)
11/21/2007 3:36:59 AM
On Tue, 20 Nov 2007 18:51:24 -0800, "Fred Marshall"
<fmarshallx@remove_the_x.acm.org> wrote:

>As I recall, boiling can be ignored until one asks "why?" about one of the 
>practicalities of it.

Exactly the process I went through.  The logic got stuck for a while
on lifting a water column strictly by the pressure differential, I
suggested getting around that via priming, but hadn't taken the next
logical step to realize that the conditions at the top of the column
would lead to boiling.   As soon as I saw a sort of obscure hint about
cavitation it occured to me that it'd easily go to full-on boil as
soon as there was a cavitation opportunity, and then there'd be
nothing to fully support the column.

Hayward's trick was to eliminate as many cavitation opportunities as
he could, including using a bellows for the pump rather than anything
with parts that would have exposed friction surfaces, and a few other
subtleties that were pretty creative.  I think it's impressive that he
went from a 10m theoretical limit to a 17m practical limit...very
cool.

>Eric's diagram Figure 3 Case A comes close enough.
>
>You draw a free body diagram of a chunk of water.
>Consider a chunk of water at the top of the water column.
>The pressure at the bottom is 1 atm. or around 15psia.
>The pressure reduces going up the water column until, at the surface the 
>pressure is zero psia.
>
>There's no such thing as negative pressure in a gas or liquid - in the gross 
>sense at least.  They have no tensile strength.  The minimum pressure 
>(theoretical at that - a perfect vacuum) is zero psia.

And that's where some other interesting stuff comes in.   Apparently
negative pressure in liquids has been demonstrated since the middle
1600s, and that's where the arguments for strong tensile strength
comes from.  Section 4.1 in Caupin's paper that I previously
mentioned, here:

http://www.lps.ens.fr/~caupin/fichiersPDF/CRPhys_2006_7_1000-1017.pdf

describes the simple experiment to demonstrate negative pressure in
liquids.   They even thought to then introduce a bubble into the
column and watch the whole thing collapse, since it's not stable in
that condition.

Hayward's pump realized something like -0.17Mpa suction in the water
to get the 17m of lift.


>Now, back to that chunk of water free body diagram.  If the pressure on one 
>side were smaller than the pressure on the other, the water would move. 
>y'know: f=ma, and it could be thus "pumped".  But, the pressure on the top 
>side can't be smaller than zero.  Turn things around and ask "at what height 
>will the pressure be zero?"  Oh! around 32 feet. There doesn't have to be a 
>void to reach this conclusion.  But, it tends to explain how a void would be 
>formed through some mechanism or other if one tried to pump thereafter.
>
>One might ask: "What happens if a piston pump "pulls" on the water after the 
>pressure reaches zero psia?"  The only thing that happens is that the piston 
>stops or breaks or a void is formed.  If there's a void and no more water to 
>boil then the void gets larger and the vacuum becomes "better" in terms of 
>the number of molecules of gas still bouncing around in there.  But it's 
>still not zero psia actually.

Agreed.  The boiling will continue in order to maintain some low
pressure, and won't stop until the pressure rises enough to exceed
boiling conditions.   It's a stable system from that perspective, and
not intuitive at first glance, at least for me it took a second
glance, at which point it became obvious.  ;)

Eric Jacobsen
Minister of Algorithms
Abineau Communications
http://www.ericjacobsen.org
0
eric.jacobsen (2636)
11/21/2007 4:00:44 AM
glen herrmannsfeldt wrote:
> John Monro wrote:
> 
>> A 'vacuum' is the lowest pressure that you can create in a pipe if you 
>> are pumping air, but with a liquid the position is entirely different 
>> as a column of liquid has a tensile strength.  A suitable pump can 
>> actually 'pull' the liquid, creating a negative pressure.
> 
>> The 28 ft. limitation comes in with water because water will boil at 
>> room temperature when a near-vacuum is applied. This means that the 
>> column of water breaks up into bubbles and the liquid component 
>> collapses to the bottom of the pipe.
> 
>> In theory it should be possible to pull an oil column much higher, 
>> even allowing for its lower density relative to water.  Because of its 
>> lower vapuur-pressure, oil will not boil under a vacuum at room 
>> temperature. In photos of oil-wells they often seem to be pumping from 
>> the top, but that is as close as I have ever been so I can't say for 
>> sure.
> 
> That is if there are no low boiling point (high vapor pressure)
> hydrocarbons (or others) in the oil.
If you wanted to go into the matter that far, you would have to consider 
the partial pressure contributed by each volatile fraction.
> 
> I always thought the oil well pumps pulled a cable that went down
> to the bottom of the well where the actual pump was.
Thanks Glen and Steve. I wondered about that, but had no information
> 
> -- glen
> 
0
11/21/2007 6:07:51 AM
I think the boiling of water is not the limiting factor, but the wate
column will simply "tear off".

Imagine a glass pipe full of mercury (which in my imagination doesn'
"boil", technically that's not correct, but the partial pressure is -very
low).
I put the pipe into a bucket full of mercury, seal with my thumb and star
to pull it out.
At a height of I think 700 mm, the mercury column drops.

The same happens with the water pump at 10 m. A real pump works EVEN WORS
when it's running dry. But still, if I fill it with water it can only reac
the performance of an ideal pump. 

-mn


0
mnentwig (306)
11/21/2007 9:07:57 AM
mnentwig wrote:
> I think the boiling of water is not the limiting factor, but the water
> column will simply "tear off".
> 
> Imagine a glass pipe full of mercury (which in my imagination doesn't
> "boil", technically that's not correct, but the partial pressure is -very-
> low).
> I put the pipe into a bucket full of mercury, seal with my thumb and start
> to pull it out.
> At a height of I think 700 mm, the mercury column drops.

I think 760mmHg is standard atmospheric pressure, but you have the right 
idea. The difference with a volatile liquid, like water, is its maximum 
height in the tube is less than its density would suggest. I think one 
atmosphere is about 10m of water, but a pump may stop working above 
about 9m because of the vapour issue.

> The same happens with the water pump at 10 m. A real pump works EVEN WORSE
> when it's running dry. But still, if I fill it with water it can only reach
> the performance of an ideal pump. 

Steve
0
steveu (1008)
11/21/2007 10:19:48 AM
>> I think 760mmHg is standard atmospheric pressure

Hehehe either the weather is really bad. Or I am high :)

-mn
0
mnentwig (306)
11/21/2007 2:42:58 PM
On Nov 20, 9:31 pm, Jerry Avins <j...@ieee.org> wrote:
> Christen Fihl wrote:
> > I think the system my parents had while I were a kid was using something=

> > called injection pump.
> > Most of the water were send back into the drill hole in a second pipe,
> > and only part of the lifted water were used at once.
>
> > Our well was 12m (40feet), and I cannot remember anything about any pump=

> > in the bottom.
> > There were 2 pipes in the drill hole, one for water going down.
> > We had to prime the system with water, if it lost water.
> > I guess the drill hole were air tight, but not sure (to raise pressure
> > in the hole).
>
> > It has been some years ago. And me getting older, I cannot remember all
> > that well ;-)
>
> > How does this sound anyway?
>
> You are describing a deep-well jet pump. We had one; my father had his
> fatal heart attack priming it. There is a venturi under water, and water
> pumped down (in our case) a one-inch line. The output of the venturi was
> a 1.5-inch line, pressured by the venturi and tied to the suction end of
> a centrifugal pump. I was lucky: the suction sprung a leak somewhere,
> and I replaces the venturi with a submersible pump. no digging was
> needed. The old one-inch line became the pump's delivery line, and the
> piece of old 1.5-inch delivery line, leak and all, became the conduit
> for the wire to power the pump. (I cut it off at the well head, where
> the wires are spliced.) The pump,a shallow-well above-ground jet, and a
> deep-well jet are shown athttp://www.femyers.com/products/sse/sse_mflconve=
rt.html
>
> Jerry
> --
> Engineering is the art of making what you want from things you can get.
> =AF=AF=AF=AF=AF=AF=AF=AF=AF=AF=AF=AF=AF=AF=AF=AF=AF=AF=AF=AF=AF=AF=AF=AF=
=AF=AF=AF=AF=AF=AF=AF=AF=AF=AF=AF=AF=AF=AF=AF=AF=AF=AF=AF=AF=AF=AF=AF=AF=AF=
=AF=AF=AF=AF=AF=AF=AF=AF=AF=AF=AF=AF=AF=AF=AF=AF=AF=AF=AF=AF=AF=AF- Hide quo=
ted text -
>
> - Show quoted text -

Hello Jerry and others,

Yes, deep well jet pumps are quite common. That is what I use to get
my water from 60 feet down. You select the injector according to depth
and flow rate of the pump. Since my well is bored (has a 24 inch
diameter), a submersable pump would twist the water line and cause it
to fail. Drilled wells on the other hand are typically 4 to 6 inches
in diameter and submersible pumps are quite common for those. There is
an attachment you put on the water/power line that retards the torque.
Drilled wells tend to be deeper than bored wells. This helps with the
drawdown that occurs when you fill your water tank.

Clay






0
physics1 (667)
11/21/2007 2:54:38 PM
On Nov 20, 11:00 pm, Eric Jacobsen <eric.jacob...@ieee.org> wrote:
> On Tue, 20 Nov 2007 18:51:24 -0800, "Fred Marshall"
>
> <fmarshallx@remove_the_x.acm.org> wrote:
> >As I recall, boiling can be ignored until one asks "why?" about one of the
> >practicalities of it.
>
> Exactly the process I went through.  The logic got stuck for a while
> on lifting a water column strictly by the pressure differential, I
> suggested getting around that via priming, but hadn't taken the next
> logical step to realize that the conditions at the top of the column
> would lead to boiling.   As soon as I saw a sort of obscure hint about
> cavitation it occured to me that it'd easily go to full-on boil as
> soon as there was a cavitation opportunity, and then there'd be
> nothing to fully support the column.
>
> Hayward's trick was to eliminate as many cavitation opportunities as
> he could, including using a bellows for the pump rather than anything
> with parts that would have exposed friction surfaces, and a few other
> subtleties that were pretty creative.  I think it's impressive that he
> went from a 10m theoretical limit to a 17m practical limit...very
> cool.
>
> >Eric's diagram Figure 3 Case A comes close enough.
>
> >You draw a free body diagram of a chunk of water.
> >Consider a chunk of water at the top of the water column.
> >The pressure at the bottom is 1 atm. or around 15psia.
> >The pressure reduces going up the water column until, at the surface the
> >pressure is zero psia.
>
> >There's no such thing as negative pressure in a gas or liquid - in the gross
> >sense at least.  They have no tensile strength.  The minimum pressure
> >(theoretical at that - a perfect vacuum) is zero psia.
>
> And that's where some other interesting stuff comes in.   Apparently
> negative pressure in liquids has been demonstrated since the middle
> 1600s, and that's where the arguments for strong tensile strength
> comes from.  Section 4.1 in Caupin's paper that I previously
> mentioned, here:
>
> http://www.lps.ens.fr/~caupin/fichiersPDF/CRPhys_2006_7_1000-1017.pdf
>
> describes the simple experiment to demonstrate negative pressure in
> liquids.   They even thought to then introduce a bubble into the
> column and watch the whole thing collapse, since it's not stable in
> that condition.
>
> Hayward's pump realized something like -0.17Mpa suction in the water
> to get the 17m of lift.
>
> >Now, back to that chunk of water free body diagram.  If the pressure on one
> >side were smaller than the pressure on the other, the water would move.
> >y'know: f=ma, and it could be thus "pumped".  But, the pressure on the top
> >side can't be smaller than zero.  Turn things around and ask "at what height
> >will the pressure be zero?"  Oh! around 32 feet. There doesn't have to be a
> >void to reach this conclusion.  But, it tends to explain how a void would be
> >formed through some mechanism or other if one tried to pump thereafter.
>
> >One might ask: "What happens if a piston pump "pulls" on the water after the
> >pressure reaches zero psia?"  The only thing that happens is that the piston
> >stops or breaks or a void is formed.  If there's a void and no more water to
> >boil then the void gets larger and the vacuum becomes "better" in terms of
> >the number of molecules of gas still bouncing around in there.  But it's
> >still not zero psia actually.
>
> Agreed.  The boiling will continue in order to maintain some low
> pressure, and won't stop until the pressure rises enough to exceed
> boiling conditions.   It's a stable system from that perspective, and
> not intuitive at first glance, at least for me it took a second
> glance, at which point it became obvious.  ;)
>
> Eric Jacobsen
> Minister of Algorithms
> Abineau Communicationshttp://www.ericjacobsen.org

Eric,

A lot of shallow wells have a practical limit of around 20 feet.
Boiling is a main problem. But also with small pressure differences,
you don't get much flow. A household well needs to deliver at least 3
gallons per minute with 5 gpm being much nicer. Certainly one may use
a large storage tank, but one wants the well's flow rate to be able to
exceed the sustained pump rate. And irrigation wells have extreme flow
rates.

Cavitation as you mentioned is actually a huge problem. Turbulent flow
in the pipe can lead to vapor locking of the pump. Plus minerals in
the water make it a little heavier than simple fresh water. I.e. salt
water 33 feet is equivalent to frest water at 34 feet.

So the common method for a well over 20 feet deep is either a
submersable or a jet pump.

Capillary action is a neat way to move water up a great height. The
California Redwood, which if I recall correctly, is the tallest living
thing and it tops out at about 350 feet. And of course these trees are
themselves growing at an altitude much higher than sealevel. So this
method works, but how fast is the transport? If you had a drilled well
(4 inch diameter) 300 feet deep, What would be the rate of production
of the well if it will filled with some material that simulated the
fiber structure of a tree? I don't know, but that answer would tell if
this approach is practical (high enough flow rate) or not.

Clay


0
physics1 (667)
11/21/2007 3:09:10 PM
Clay wrote:

Clay,

> Yes, deep well jet pumps are quite common. That is what I use to get
> my water from 60 feet down. You select the injector according to depth
> and flow rate of the pump. Since my well is bored (has a 24 inch
> diameter), a submersable pump would twist the water line and cause it
> to fail. Drilled wells on the other hand are typically 4 to 6 inches
> in diameter and submersible pumps are quite common for those. There is
> an attachment you put on the water/power line that retards the torque.
> Drilled wells tend to be deeper than bored wells. This helps with the
> drawdown that occurs when you fill your water tank.

My well was drilled. It went down to 280 feet before hitting adequate 
water (there was a trickle of sulfurous water at about 30 feet that was 
capped off) and when it hit the seam, water rose to within 40 feet of 
the surface. Pumping at about 20 gallons/minute dropped the level about 
a foot. The jet was set down about 50 feet, and it worked fine for 
years. During a summer of drought, many wells went dry, including ours. 
We lowered the jet another 15 feet and installed an outside hose cock. 
(The only one had been in the pump house.) About eight neighbors got 
their water from us for about two weeks.

Jerry
-- 
Engineering is the art of making what you want from things you can get.
�����������������������������������������������������������������������
0
jya (12871)
11/21/2007 5:17:20 PM
Fred Marshall wrote:
> As I recall, boiling can be ignored until one asks "why?" about one of the 
> practicalities of it.
> 
> Eric's diagram Figure 3 Case A comes close enough.
> 
> You draw a free body diagram of a chunk of water.
> Consider a chunk of water at the top of the water column.
> The pressure at the bottom is 1 atm. or around 15psia.
> The pressure reduces going up the water column until, at the surface the 
> pressure is zero psia.
> 
> There's no such thing as negative pressure in a gas or liquid - in the gross 
> sense at least.  They have no tensile strength.  The minimum pressure 
> (theoretical at that - a perfect vacuum) is zero psia.

Not much, anyway. Liquids will sustain a little tension, at least for a 
short while. Usually, it has negligible effect. Sometimes the effect is 
dramatic, but then it's usually surface (not internal) tension at play.

Consider a soap bubble. Thermodynamics tells us that a bubble can't 
consist of a pure liquid; that's why we need soap to form one. A 
simplistic analysis predicts that gravity brings the water in the film 
to the bottom. With no top, there's no bubble. In a pure liquid, that's 
what happens. In a mixture, the properties needn't be everywhere the 
same, and with soap, the film tension at the top is enough higher than 
the tension at the bottom to hold the water up.

   ...

Jerry

P.S. Soap molecules have a hydrophilic and a hydrophobic end. When 
enough soap is dissolved in water, a monolayer of soap forms at the 
air-water interface, with the hydrophobic ends facing the air. This 
lowers the surface tension (thereby allowing the solution to wet 
surfaces that clean water won't). In a bubble, gravity drains the upper 
part of the film, making it thin enough to disrupt the monolayer, so 
raising the surface tension. The differential surface tension supports 
the film of water/soap solution.
-- 
Engineering is the art of making what you want from things you can get.
�����������������������������������������������������������������������
0
jya (12871)
11/21/2007 5:35:34 PM
On Wed, 21 Nov 2007 07:09:10 -0800 (PST), Clay <physics@bellsouth.net>
wrote:

>On Nov 20, 11:00 pm, Eric Jacobsen <eric.jacob...@ieee.org> wrote:
>> On Tue, 20 Nov 2007 18:51:24 -0800, "Fred Marshall"
>>
>> <fmarshallx@remove_the_x.acm.org> wrote:
>> >As I recall, boiling can be ignored until one asks "why?" about one of the
>> >practicalities of it.
>>
>> Exactly the process I went through.  The logic got stuck for a while
>> on lifting a water column strictly by the pressure differential, I
>> suggested getting around that via priming, but hadn't taken the next
>> logical step to realize that the conditions at the top of the column
>> would lead to boiling.   As soon as I saw a sort of obscure hint about
>> cavitation it occured to me that it'd easily go to full-on boil as
>> soon as there was a cavitation opportunity, and then there'd be
>> nothing to fully support the column.
>>
>> Hayward's trick was to eliminate as many cavitation opportunities as
>> he could, including using a bellows for the pump rather than anything
>> with parts that would have exposed friction surfaces, and a few other
>> subtleties that were pretty creative.  I think it's impressive that he
>> went from a 10m theoretical limit to a 17m practical limit...very
>> cool.
>>
>> >Eric's diagram Figure 3 Case A comes close enough.
>>
>> >You draw a free body diagram of a chunk of water.
>> >Consider a chunk of water at the top of the water column.
>> >The pressure at the bottom is 1 atm. or around 15psia.
>> >The pressure reduces going up the water column until, at the surface the
>> >pressure is zero psia.
>>
>> >There's no such thing as negative pressure in a gas or liquid - in the gross
>> >sense at least.  They have no tensile strength.  The minimum pressure
>> >(theoretical at that - a perfect vacuum) is zero psia.
>>
>> And that's where some other interesting stuff comes in.   Apparently
>> negative pressure in liquids has been demonstrated since the middle
>> 1600s, and that's where the arguments for strong tensile strength
>> comes from.  Section 4.1 in Caupin's paper that I previously
>> mentioned, here:
>>
>> http://www.lps.ens.fr/~caupin/fichiersPDF/CRPhys_2006_7_1000-1017.pdf
>>
>> describes the simple experiment to demonstrate negative pressure in
>> liquids.   They even thought to then introduce a bubble into the
>> column and watch the whole thing collapse, since it's not stable in
>> that condition.
>>
>> Hayward's pump realized something like -0.17Mpa suction in the water
>> to get the 17m of lift.
>>
>> >Now, back to that chunk of water free body diagram.  If the pressure on one
>> >side were smaller than the pressure on the other, the water would move.
>> >y'know: f=ma, and it could be thus "pumped".  But, the pressure on the top
>> >side can't be smaller than zero.  Turn things around and ask "at what height
>> >will the pressure be zero?"  Oh! around 32 feet. There doesn't have to be a
>> >void to reach this conclusion.  But, it tends to explain how a void would be
>> >formed through some mechanism or other if one tried to pump thereafter.
>>
>> >One might ask: "What happens if a piston pump "pulls" on the water after the
>> >pressure reaches zero psia?"  The only thing that happens is that the piston
>> >stops or breaks or a void is formed.  If there's a void and no more water to
>> >boil then the void gets larger and the vacuum becomes "better" in terms of
>> >the number of molecules of gas still bouncing around in there.  But it's
>> >still not zero psia actually.
>>
>> Agreed.  The boiling will continue in order to maintain some low
>> pressure, and won't stop until the pressure rises enough to exceed
>> boiling conditions.   It's a stable system from that perspective, and
>> not intuitive at first glance, at least for me it took a second
>> glance, at which point it became obvious.  ;)
>>
>> Eric Jacobsen
>> Minister of Algorithms
>> Abineau Communicationshttp://www.ericjacobsen.org
>
>Eric,
>
>A lot of shallow wells have a practical limit of around 20 feet.
>Boiling is a main problem. But also with small pressure differences,
>you don't get much flow. A household well needs to deliver at least 3
>gallons per minute with 5 gpm being much nicer. Certainly one may use
>a large storage tank, but one wants the well's flow rate to be able to
>exceed the sustained pump rate. And irrigation wells have extreme flow
>rates.
>
>Cavitation as you mentioned is actually a huge problem. Turbulent flow
>in the pipe can lead to vapor locking of the pump. Plus minerals in
>the water make it a little heavier than simple fresh water. I.e. salt
>water 33 feet is equivalent to frest water at 34 feet.
>
>So the common method for a well over 20 feet deep is either a
>submersable or a jet pump.

Somehow I just knew there'd be expertise on this subject in this
crowd.   I've not been disappointed.  ;)

>Capillary action is a neat way to move water up a great height. The
>California Redwood, which if I recall correctly, is the tallest living
>thing and it tops out at about 350 feet. And of course these trees are
>themselves growing at an altitude much higher than sealevel. So this
>method works, but how fast is the transport? If you had a drilled well
>(4 inch diameter) 300 feet deep, What would be the rate of production
>of the well if it will filled with some material that simulated the
>fiber structure of a tree? I don't know, but that answer would tell if
>this approach is practical (high enough flow rate) or not.

I'm guessing the flow rate is low as well.   Without a need for a high
flow rate, trees can use whatever technique just meets their
requirements.

Nevertheless, I've no idea how much water a redwood would pump in a
day.   I can imagine on a hot, dry day that the structure of a giant
redwood could be losing a lot of water, but maybe they're really
efficient at minimizing loss as well.

Another thing occurred to me last night, which is that the negative
water pressure supported along the length of the tree probably
contributes to the tendency of trees to explode when hit by lightning.
I've always heard that it's the water vaporizing that does this, but
it's not just vaporizing it's essentially detonating (well, I hope the
gist of the distinction makes sense), since it's already in a
metastable superheated state in the tree.   A lightning bolt comes
along and adds energy (and a lot of cavitation) and BOOM!, instant
vaporization.   It doesn't even need to be heated to change the state
from liquid to vapor, it just gets triggered.

Eric Jacobsen
Minister of Algorithms
Abineau Communications
http://www.ericjacobsen.org
0
eric.jacobsen (2636)
11/21/2007 5:49:06 PM
On Nov 20, 4:43 pm, Eric Jacobsen <eric.jacob...@ieee.org> wrote:
> Hey, smart people.
>
> I've been having a discussion with a firefighter that's gone something
> like this (heavily paraphrased):
>
> He:  You know you can only lift water about 28ft with a pump?  It's
> physically impossible to pump it higher than that if the pump is at
> the top of the lift.
>
> (e.g., a pump at the top of a well, something like that)
>
> Me:  I think that's only a limit for a vacuum pump.   Doesn't it work
> if you prime the pump from the top?
>
> He:  I repeat, it's physically impossible to pump water higher than
> 30ft with an elevated pump.
>
....
> So far the response is simply, "That won't work."
>
> Apparently common firefighter training conveys that this is
> impossible, but I'm failing to see why.

Eric, i hadn't gone through the other responses closely, but i hadn't
seen this term:  "Water barometer":

i can't find a really good link but this says it:

http://cancerweb.ncl.ac.uk/cgi-bin/omd?water+barometer


why is it that a Mercury barometer gets to a height of 760 mm?  what
would happen if you hooked up a vacuum pump up to the top of the
mercury barometer and sucked even harder?  can you create a better
vacuum that a pure vacuum?  it's the same reason that H20 barometer is
up at about 10 meters.  you have a column of air (about 200 kilometers
high) pushing down on the same spot that a column of Hg or H20 is, and
all 3 columns weigh the same.

r b-j
0
rbj (4086)
11/22/2007 3:18:14 AM
Jerry Avins <jya@ieee.org> writes:

> Heinrich Wolf wrote:
>> Eric Jacobsen <eric.jacobsen@ieee.org> writes:
>> ...
>> I just did a simple experiment in my kitchen which, I think,
>> clearly demonstrates the tensile strength of water.
>> I filled a class of _cold_ water up next to the rim.
>> (Temperature was about eight Celsius.)  Then I looked for the next
>> thing that might be appropriate and got hold of an eating-knive, where
>> the end of the handle is of metal, a little rounded, and about 8x12
>> millimeters in crossection.  I emerged the end of the handle a little
>> into the water and pulled it slowly upwards, holding the knive in
>> vertical position.  The water kept connected to the handle until it's
>> end was 2 or 3 millimeters above the surface.  So I ``pulled'' water,
>> which, I claim, requires ``tensile strength''.
>
> You demonstrated surface tension. Search for a way to measure surface
> tension with a wire frame one centimeter wide and an analytical
> balance. The general topic id physical chemistry.

You seem to refer to those experiments where the force needed to pull
a flat sling of wire from the surface is measured?  If so, that's not
the essential thing in my demonstration.

Of course surface tension is just another macroscopic quantity that
originates from inter-molecular forces, same as tensile strength does.

Surface tension is defined as the specific work required to increase
the surface.  Therefore, when one wants to measure surface tension,
one makes the ratio circumference/magnitude of the area that touches
the water as big as possible: take a thin wire or a stripe of metal
sharpened at one edge like a knive's blade.

I tried to do the opposite, I tried to make this ratio small.

Of course, surface tension came into play too, and to me, the fun here
is to find out without much equipment what is more important: surface
tension or tensile strength.

As I do not have an appropriate balance at hands, I make the
assumption that the force that breaks the column (thread) of water is
approximatly proportional to the mass of water that was lifted above
the original surface.

If the strength of this column under tension comes from surface
tension, then this strength is proportional to the circumference of
the column.  Otherwise, if it comes from tensionl strength, then the
strength is proportional to the crosssection of the column.

To test this, I got two round rods of iron, one and four centimeters
in diameter, where on each I filed one face flat to have comparable
conditions.  Using these rods the same way I did with the eating knive
showed that I could lift both about 3 millimeters above the surface
until the thread broke.  So it should have been essentially tensional
strength.

-- 
hw
0
hwmuell (37)
11/22/2007 10:30:58 PM
Eric Jacobsen <eric.jacobsen@ieee.org> writes:

> On Wed, 21 Nov 2007 01:58:09 +0100, Heinrich Wolf
> <hwmuell@willis-werkstaette.de> wrote:
>
>>Eric Jacobsen <eric.jacobsen@ieee.org> writes:
>>
>>> On Tue, 20 Nov 2007 17:32:31 -0500, Jerry Avins <jya@ieee.org> wrote:
>>>
>>>>Eric Jacobsen wrote:
>>>>> ......
>>>>>       I've found little on the
>>>>> internet with the searches I've tried, with the exception of how trees
>>>>> pump water as high as, apparently, 450m under tension (which is pretty
>>>>> cool, btw).
>>
>>If this refers to newer work on the subject, I would be very
>>interested to find it too.  ....
>
> Here are some of the interesting urls I found:
> ...

Thank you very much.  The paper by the frenchmen seems to be very
usefull to me. At a first glance, I got a phrase for the thing I am
looking for: ``Ascent of sap in trees''.

-- 
hw
0
hwmuell (37)
11/22/2007 10:31:02 PM
Eric Jacobsen <eric.jacobsen@ieee.org> writes:

> On Wed, 21 Nov 2007 07:09:10 -0800 (PST), Clay <physics@bellsouth.net>
> wrote:
>
>>On Nov 20, 11:00 pm, Eric Jacobsen <eric.jacob...@ieee.org> wrote:
>>> On Tue, 20 Nov 2007 18:51:24 -0800, "Fred Marshall"
>>>
> ...
> Another thing occurred to me last night, which is that the negative
> water pressure supported along the length of the tree probably
> contributes to the tendency of trees to explode when hit by lightning.
> I've always heard that it's the water vaporizing that does this, but
> it's not just vaporizing it's essentially detonating (well, I hope the
> gist of the distinction makes sense), since it's already in a
> metastable superheated state in the tree.   A lightning bolt comes
> along and adds energy (and a lot of cavitation) and BOOM!, instant
> vaporization.   It doesn't even need to be heated to change the state
> from liquid to vapor, it just gets triggered.

You might be interested in what I have seen at quite a few trees
(european kind of spruce, 15 to 30 meters high) hit by lightning and
at a rafter of a house.

On trees lightning forms a channel close to the surface which seems to
follow roughly the direction of the fibers of the wood; i.e in the
lower part it tends to wind around the tree as the grain usually does.
Stripes of wood are ``blown'' out.  The crossection of the channel
seems to be constant along the height of the tree, it's usually about
the width of a big man's hand.

The house, and the rafter, was almost 200 years old and hit in June,
when it is hot and wood was really dry.  Again a channel was formed
that seems to follow the grain of the wood and stripes scattered
around.  The width of the channel is less then what I saw in trees,
about 5 centimeters.  To me, this seems no surprise, as some of the
charge may well have flown along other paths.  But otherwise all
looked quite similar to the effect on trees.  So I think it's just
evaporation and heating of gases inside the wood.

-- 
hw
0
hwmuell (37)
11/22/2007 10:31:05 PM
Heinrich Wolf wrote:
> Jerry Avins <jya@ieee.org> writes:
> 
>> Heinrich Wolf wrote:
>>> Eric Jacobsen <eric.jacobsen@ieee.org> writes:
>>> ...
>>> I just did a simple experiment in my kitchen which, I think,
>>> clearly demonstrates the tensile strength of water.
>>> I filled a class of _cold_ water up next to the rim.
>>> (Temperature was about eight Celsius.)  Then I looked for the next
>>> thing that might be appropriate and got hold of an eating-knive, where
>>> the end of the handle is of metal, a little rounded, and about 8x12
>>> millimeters in crossection.  I emerged the end of the handle a little
>>> into the water and pulled it slowly upwards, holding the knive in
>>> vertical position.  The water kept connected to the handle until it's
>>> end was 2 or 3 millimeters above the surface.  So I ``pulled'' water,
>>> which, I claim, requires ``tensile strength''.
>> You demonstrated surface tension. Search for a way to measure surface
>> tension with a wire frame one centimeter wide and an analytical
>> balance. The general topic id physical chemistry.
> 
> You seem to refer to those experiments where the force needed to pull
> a flat sling of wire from the surface is measured?  If so, that's not
> the essential thing in my demonstration.
> 
> Of course surface tension is just another macroscopic quantity that
> originates from inter-molecular forces, same as tensile strength does.
> 
> Surface tension is defined as the specific work required to increase
> the surface.

Not exactly; the units don't match. Surface tension is measures in 
dynes/centimeter (newtons/meter).

>                 Therefore, when one wants to measure surface tension,
> one makes the ratio circumference/magnitude of the area that touches
> the water as big as possible: take a thin wire or a stripe of metal
> sharpened at one edge like a knive's blade.
> 
> I tried to do the opposite, I tried to make this ratio small.
> 
> Of course, surface tension came into play too, and to me, the fun here
> is to find out without much equipment what is more important: surface
> tension or tensile strength.
> 
> As I do not have an appropriate balance at hands, I make the
> assumption that the force that breaks the column (thread) of water is
> approximatly proportional to the mass of water that was lifted above
> the original surface.

Surely the mass depends on the diameter of the tube in a way that bulk 
tensile strength does not.

> If the strength of this column under tension comes from surface
> tension, then this strength is proportional to the circumference of
> the column.  Otherwise, if it comes from tensionl strength, then the
> strength is proportional to the crosssection of the column.
> 
> To test this, I got two round rods of iron, one and four centimeters
> in diameter, where on each I filed one face flat to have comparable
> conditions.  Using these rods the same way I did with the eating knive
> showed that I could lift both about 3 millimeters above the surface
> until the thread broke.  So it should have been essentially tensional
> strength.

It was the capillary effect of surface tension. Try the same experiments 
with a wax coating on the rod. There will be no lift without wetting.

Jerry
-- 
Engineering is the art of making what you want from things you can get.
�����������������������������������������������������������������������
0
jya (12871)
11/22/2007 11:19:54 PM
Jerry Avins <jya@ieee.org> writes:
>Heinrich Wolf wrote:
>> Jerry Avins <jya@ieee.org> writes:
>> 
>>> Heinrich Wolf wrote:
>>>> Eric Jacobsen <eric.jacobsen@ieee.org> writes:
>>>> ...
>>>> I just did a simple experiment in my kitchen which, I think,
>>>> clearly demonstrates the tensile strength of water.
>>>> I filled a class of _cold_ water up next to the rim.
>>>> (Temperature was about eight Celsius.)  Then I looked for the next
>>>> thing that might be appropriate and got hold of an eating-knive, where
>>>> the end of the handle is of metal, a little rounded, and about 8x12
>>>> millimeters in crossection.  I emerged the end of the handle a little
>>>> into the water and pulled it slowly upwards, holding the knive in
>>>> vertical position.  The water kept connected to the handle until it's
>>>> end was 2 or 3 millimeters above the surface.  So I ``pulled'' water,
>>>> which, I claim, requires ``tensile strength''.
>>> You demonstrated surface tension. Search for a way to measure surface
>>> tension with a wire frame one centimeter wide and an analytical
>>> balance. The general topic id physical chemistry.
>> 
>> You seem to refer to those experiments where the force needed to pull
>> a flat sling of wire from the surface is measured?  If so, that's not
>> the essential thing in my demonstration.
>> 
>> Of course surface tension is just another macroscopic quantity that
>> originates from inter-molecular forces, same as tensile strength does.
>> 
>> Surface tension is defined as the specific work required to increase
>> the surface.
>
> Not exactly; the units don't match. Surface tension is measures in 
> dynes/centimeter (newtons/meter).

Jerry, please multiply nominator and denominator of this fraction with
unit length ... ;-)

>> ....
>> As I do not have an appropriate balance at hands, I make the
>> assumption that the force that breaks the column (thread) of water is
>> approximatly proportional to the mass of water that was lifted above
>> the original surface.
>
> Surely the mass depends on the diameter of the tube in a way that bulk 
> tensile strength does not.

What tube? 

But you are right: here is a flaw in my argument.  Now I see that you
can explain the effects I reported by surface tension alone.  So there
was no ``demonstration of tensile strength''.  Thank you for your
input.

-- 
hw
0
hw1 (14)
11/25/2007 10:56:00 PM
Heinrich Wolf wrote:

>         ...  Now I see that you
> can explain the effects I reported by surface tension alone.  So there
> was no ``demonstration of tensile strength''.  Thank you for your
> input.

I won't beat a dead horse then. You're welcome.

Jerry
-- 
Engineering is the art of making what you want from things you can get.
�����������������������������������������������������������������������
0
jya (12871)
11/26/2007 3:17:17 AM
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Cheers guys. I'm not running DHCP, I should have said I've pegged all my IP's (in an attempt to keep it simple). I do recall seeing lease times which is why I think its one of these 180 minute issues but goodness knows where. Yeh, I've tried the various MS discussion groups but its such a diverse environment I've never had a reply, let alone any help. I guess its a case of knowing how to ask the question as much as understanding the answer. I'll keep plugging away. I can't help feeling its some obscure check box somewhere. * To join/leave the list, ...

No pills, no pumps
Penis Enlargement announcement http://www.etumex.com/pt/ OK, so you've got a Ph.D. Now, don't touch anything. Delusions of grandeur make me feel a lot better about myself. Vanity makes us do more things against inclination than reason. Don't let the bastards grind you down. ...

is correct this Pumping Lemma? and this?
Prove that L = {a^n b^n+2 | n > 0} on alphabet {a, b} is not regular with Pumping Lemma. For all n exist a word | not satisfy the P.L. with three rule: 1. |xy| <= n 2. |y| > 0 3. xy^iz belong L for all i >= 0 Factorize w = xyz = a^n-k a^k b^n+2 with 0 < k <= n and this expression satisfy rule 1 and 2 but not 3, therefore xz = a^n-k b^n+2 with k > 0 and xz not belong L... is not regular is it correct? The other questions is: an authome DFA with this peculiarity: L = {a, b} with odd word-length and end with ba OR word-length is a multiple of 3. What is the correct...

Pumping Lemma Palindrome
I�m having difficulty proving L={ww^r | w an element of (0,1)* ending in a 10} where w^r is w reverse is not a regular language using the pumping lemma. I am able to show that L={ww^r | w an element of (0,1)*} is not regular. Is it safe to assume that since palindromes are not regular, specified ending palindromes are also not regular? Any advice on how to solve this problem would be greatly appreciated. TIA. "labrat" <Scezic@hotmail.com> wrote in message news:108opslqj7c4472@corp.supernews.com... > Any advice on how to solve this problem would be greatly appreciated. T...

Posessives [Totally OT]
Recently in these discussions a diversion was a discussion regarding where to place the apostrophe and whether an additional "s" should be added when forming the possessive of a name. I'm amused that here I am at Sherlock's in Austin and the restrooms are labelled "Mens" and "Ladies", but that isn't as bad not far away a place offers "hot dog's"! -- James Leo Ryan ..... Austin, Texas ..... taliesinsoft@me.com On Wed, 17 Sep 2008 16:28:07 -0500, TaliesinSoft <taliesinsoft@mac.coom> wrote: >Recently in these discussions a...

Web resources about - TOTALLY OT: Pumping water with an elevated pump. - comp.dsp

Elevated railway - Wikipedia, the free encyclopedia
An elevated railway (also known in Europe as overhead railway ) is a form of rapid transit railway with the tracks built above street level on ...

Elevated – The Dead Simple L Train Tracker for Chicago’s CTA on the App Store on iTunes
Get Elevated – The Dead Simple L Train Tracker for Chicago’s CTA on the App Store. See screenshots and ratings, and read customer reviews.

bronx-elevated-train-tracks-2
Explore dandeluca's photos on Flickr. dandeluca has uploaded 7532 photos to Flickr.

Great Museums: Elevated Thinking: The High Line in New York City - YouTube
Narrated by actress Susan Sarandon, this hour-long documentary film showcases the High Line, a most unusual and unlikely public park. Since opening ...

UAE Friday sermon: Islam elevated status of women in society - The National
ABU DHABI // The advent of Islam led to the elevation of women’s status in society, worshippers will be told during Friday’s sermon. The sermon ...

Adam Schneider elevated to St Kilda's senior list
St Kilda coach Alan Richardson is &quot;incredibly frustrated&quot; that he cannot name rookie-listed Jack Sinclair in the Saints' line-up this ...

World Cup opener elevated Tim Cahill to greatest-ever Socceroo
Great: notable; remarkable; exceptionally outstanding. Tim Cahill has become the greatest ever Socceroo.

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Elevated 8 Chifley bad for city, say planners
The designers of Sydney's newest office tower are under fire from urban planners for not encouraging street-level activity and for creating an ...

$1.6 billion elevated rail project to replace level crossings on Dandenong line
Elevated trains will run nine metres above street level along the Dandenong Pakenham line.

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