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Old 10-02-2010, 14:38   #31
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What you can imagine is within reach..

Anjou ! ,
I love your thinking!
Perhaps it does not make sense when the conventional wisdome tought by us and measured by our " classically trained brains kicks in, BUT,all of a sudden nano technology comes into play and we are all changing the Known or common Paradigm.

Human frontiers are constant changing due the bravery in individuals having the stomach of daring thinking out of the box.

Thanks for the thread and for my learning of possibilities in nanotech when it comes to Watermaking.

To give you someting to think about:

Will nanotech as described by the post by anotherT34C be the awnser when it comes to the really big question of recycling ???

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Old 10-02-2010, 14:55   #32
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While I love the concept of the carbon nanotube based membrane, I'm not sure you should just throw out the old systems just yet. There are engineering tricks that are used on the older style systems as "work around" for the problems mentioned by the carbon nanotube guys.

Carbon nanotubes arn't going to change the process of osmotis. The osmotic pressure is what causes sea water supplied RO units to need so much pressure.

Nature likes for everything to be even. Water with no salt in it will try to go through a membrane to water with salt in it, untill the concentration of salt is the same on both sides of the membrane. This would take all your freshwater, and make the salt water less salty. Clearly that is NOT want we want to happen. So we add a pump, and increase the pressure on the salty side of the membrane, untill we generate more pressure than the osmotic pressure. That forces the water through the membrane, and into the freashwater tank. It's backwards osmosis, or Reverse Osmosis.

The carbon nanotubes won't change that process. They just allow you to design a membrane with more optimized. There are ways around that now, not as elegent, or as efficent, but still workable. They utalize a cheaper membrane, but with more surface area. There are chemical and mechenical treatments that are used to plug oversized pores, and things of that nature.

All in all, the nanotube process looks useful for hikers, and survival type equipment. It could be used for a smaller unit on a yacht, but I don't think it would lower costs, or improve energy efficency. At least not untill the cost of making carbon nanotubes crashs. Course they claim to have similar costs to the traditional membranes, but I remain skeptical.

Still, REALLY cool!
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Old 10-02-2010, 17:25   #33
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Originally Posted by ViribusUnitis View Post
While I love the concept of the carbon nanotube based membrane, I'm not sure you should just throw out the old systems just yet. There are engineering tricks that are used on the older style systems as "work around" for the problems mentioned by the carbon nanotube guys.

Carbon nanotubes arn't going to change the process of osmotis. The osmotic pressure is what causes sea water supplied RO units to need so much pressure.

Nature likes for everything to be even. Water with no salt in it will try to go through a membrane to water with salt in it, untill the concentration of salt is the same on both sides of the membrane. This would take all your freshwater, and make the salt water less salty. Clearly that is NOT want we want to happen. So we add a pump, and increase the pressure on the salty side of the membrane, untill we generate more pressure than the osmotic pressure. That forces the water through the membrane, and into the freashwater tank. It's backwards osmosis, or Reverse Osmosis.

The carbon nanotubes won't change that process. They just allow you to design a membrane with more optimized. There are ways around that now, not as elegent, or as efficent, but still workable. They utalize a cheaper membrane, but with more surface area. There are chemical and mechenical treatments that are used to plug oversized pores, and things of that nature.

All in all, the nanotube process looks useful for hikers, and survival type equipment. It could be used for a smaller unit on a yacht, but I don't think it would lower costs, or improve energy efficency. At least not untill the cost of making carbon nanotubes crashs. Course they claim to have similar costs to the traditional membranes, but I remain skeptical.

Still, REALLY cool!
Dittos.

P.S. Banning water. Pretty funny.
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Old 10-02-2010, 18:06   #34
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A Hot Debate about Condensation

Quote:
anjou, she say:
Aircraft con trails are condensed vapour.
The separate oxygen and 2 hydrogen elements in the atmosphere have been pressed together to make water.
Anjou, from one non-scientist to another: nice try, but there's a problem with the premise. That's not how a con(densation) trail is formed. I'm surprised you engineer-types didn't catch this from the onset.

A con trail is condensed water vapor, but a con trail is not created by the leading edge of an airplane wing pressing free oxygen and free hydrogen molecules together. It is created by the water vapor (which is a main product of the internal combustion of hydrocarbon fuel) in the aircraft's exhaust cooling until it becomes visible, like a little cloud. The same thing happens behind your car on a cold day.

Jet engine spits out water vapor, it condenses, we see it. If the cooling is not really fast, we notice quite a space between the jet and the formation of the trail.

So approaching water-making by using the example of con trails would mean we plan to somehow capture our engine exhaust and collect the resulting condensation: Lord, what kind of a contraption would that be?
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Old 11-02-2010, 02:29   #35
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OK - I'm not a physicist but I read Physics at university.

The original poster said "All thats needed is either a pressure pump to force 2 x H and 1 x O molecules together at the right temperature or a canister of each gas and a mixing chamber".

This is the wrong end of the problem. Hydrogen and oxygen will combine very, very easily. The Hindenberg was a good example of this. An envelope filled with hydrogen in an oxygen atmosphere (the air you are breathing right now is 21% oxygen). All that was needed was some energy to initiate the reaction between the two gases and the heat released by their combination enable more hydrogen to start reacting. It is self sustaining.

Getting hydrogen and oxygen to combine is simple - possibly too simple, that is why it is so dangerous. You can do it in your kitchen with a matchstick.

Now, keep thinking of the Hindenberg. When all that hydrogren and oxygen combined to make water, it released enormous amounts of heat. That heat was created because the energy needed to bond 2 hydrogens to one oxygen (at the molecular level) is far, far less than the energy available to bond hydrogen to hydrogen and oxygen to oxygen. Free hydrogen and free oxygen are vanishingly rare. Hydrogen comes as H2 (two atoms joined) and oxygen as O2 (two atoms joined).

So to make water we need 4 hydrogen atoms and two oxygen atoms

2H2 + O2 -> 2H2O

To split water back to hydrogen and oxygen you need to put IN the same amount of energy that you got out by combining them. (Actually you need more but I'm simplifying)

Now back to the Hindenberg. To produce the Hydrogen needed to fill the Hindenberg you would need as much energy to spilt the water as the Hindenburg gave out when she burned.

This is the major problem with fuel cells. They work - no one disputes it, but you get less energy back than what you expended to get the hydrogen in the first place.
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Old 11-02-2010, 02:35   #36
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Actually there are two additional problems with hydrogen

1. The molecules are so small that they pass through most other materials. This means that even steel cylinders leak hydrogen. Hydrogen stored under pressure merely leaks faster.

2. Hydrogen causes many metals to become brittle which was the problem with galvininsing steel for many years. This used to be done electrolytically and produced free hydrogen at the cathode which embrittled the steel.
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Old 11-02-2010, 03:03   #37
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You guys must have paid a lot more attention in school than I did!
I'm not worthy ..bow...bow...
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Old 11-02-2010, 03:28   #38
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I was thinking of making a pig drink seawater and then collecting his sweat....


seriously, how do marine mammals maintain their biological water ratios? they don't drink fresh water, right? What percentage of a whale is fresh water........

and where did it come from?

Thats the kind of questions that come to my mind, if we are looking for a 'new' technology. The ocean is full of mammals, that are, what, 90% water, and yet they have no source of fresh water...
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Old 11-02-2010, 04:07   #39
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Not quite true.
Its pressure not the engine combustion which makes con trails.
Fast jets make con trails even at the wing tips where the vorticies squeeze the molecules together untill they are so heavy and become water droplets.

Thanks Mintyspilot. I shall read it again later till it all sinks in and makes sense.
I need more tutoring in chemistry and physics.

I guess its all about Boyles law and you cant get out more than you put in, ......except thats not quite true. But thats another story and I need to find the weblink to explain better. oh, well ok then but quickly

About 15 years ago, a heating engineer was in a plant room to do some servicing and he put his hand on what he knew to be a cold feed pipe, and it was almost too hot to touch. He double checked there was no crossover or back flow from anther system, and there wasnt.
He gave a lot of thought to this and discovered there was high frequency water hammer in the cold system and the friction generated the heat.
ok, fast forward.......he made a device like a washing machine, with an inner and outer drum. The inner drum revolved at very high speed, many thousands of RPM and into this he injected a mist of water. It spun out through the holes in the inner drum, and blasted against the outer drum. It caused a lot of heat to be generated in the water which turned to steam.

He build a working prototype and installed it at his local fire dept, where they were only too willing to use the hot water. a small unit the size of a TV set made more than enough hot water.
He worte a paper on it and published. The science comuniity were in awe and went to see it work.
They marvelled at it and then shook heads and said it was a fake, fraud etc because it broke Boyles law.
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Old 11-02-2010, 04:21   #40
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" I guess its all about Boyles law and you cant get out more than you put in"

In that case look up Thermodynamics (particularly the 2nd law on ENTROPY) rather then Boyle's Law. Boyle's law is part of the simple kinetic theory of gases and relates pressures and volumes

Thermodynamics - Wikipedia, the free encyclopedia

I should also point out that I hold a solo rating in gliders so ask away about aviation stuff....


James said: "You guys must have paid a lot more attention in school than I did!"

Swings and roundabouts matey - I know bugger all about sailing, that's why I'm spending time on these forums.
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Old 11-02-2010, 04:43   #41
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Funny how serious some of the postings appear. Never knew we had this many cutting edge PhD researchers here? There's going to be major wars over water in our lifetime. So I'm sure a lot of attention being given to the making of water way beyound the concerns of some boaters. :-)
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Old 11-02-2010, 05:27   #42
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Quote:
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...
Its pressure not the engine combustion which makes con trails.
Fast jets make con trails even at the wing tips where the vorticies squeeze the molecules together untill they are so heavy and become water droplets ...
Actually, it can be both.

Contrails form when hot humid air from aircraft engine exhaust mixes with environmental air of low vapour pressure, and low temperature. Vapour pressure is the amount of pressure that is exerted by water vapour itself (as opposed to atmospheric, or barometric, pressure which is due to the weight of the entire atmosphere above you). The mixing occurs directly behind the plane due to the turbulence generated by the engine. If condensation (conversion from a gas to a liquid) occurs, then a contrail becomes visible. Since air temperatures at these high atmospheric levels are very cold (generally colder than -40 F), only a small amount of liquid is necessary for condensation to occur. Water is a normal byproduct of combustion in engines.

The swirling pattern in a contrail is caused by the vortices coming from the tip of the aircraft. This is due to the difference in pressure (“lift”) caused by the curved foil shape of the wing.

If contrails persist for a long enough period of time, say on the order of an hour or more, they can spread out across the sky, due to the prevailing winds at the level at which they formed.

Of interest to Sailors:


If a contrail is persistent or persistently spreading, then the upper atmosphere contains large amounts of moisture.
If a contrail is short-lived, then the upper atmosphere is relatively dry.

On days where the contrails disappear quickly or don't even form, we can expect continuing good weather (dry upper atmosphere).

On days where they persist, a change in the weather pattern and/or precipitation may be expected (moist upper atmosphere - near saturation).
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Old 11-02-2010, 05:35   #43
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Quote:
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Actually, it can be both.

Contrails form when hot humid air from aircraft engine exhaust mixes with environmental air of low vapour pressure, and low temperature. Vapour pressure is the amount of pressure that is exerted by water vapour itself (as opposed to atmospheric, or barometric, pressure which is due to the weight of the entire atmosphere above you). The mixing occurs directly behind the plane due to the turbulence generated by the engine. If condensation (conversion from a gas to a liquid) occurs, then a contrail becomes visible. Since air temperatures at these high atmospheric levels are very cold (generally colder than -40 F), only a small amount of liquid is necessary for condensation to occur. Water is a normal byproduct of combustion in engines.

The swirling pattern in a contrail is caused by the vortices coming from the tip of the aircraft. This is due to the difference in pressure (“lift”) caused by the curved foil shape of the wing.

If contrails persist for a long enough period of time, say on the order of an hour or more, they can spread out across the sky, due to the prevailing winds at the level at which they formed.

Of interest to Sailors:

If a contrail is persistent or persistently spreading, then the upper atmosphere contains large amounts of moisture.
If a contrail is short-lived, then the upper atmosphere is relatively dry.

On days where the contrails disappear quickly or don't even form, we can expect continuing good weather (dry upper atmosphere).

On days where they persist, a change in the weather pattern and/or precipitation may be expected (moist upper atmosphere - near saturation).
OK...thats some good forecasting technique.
Gord you always amaze me.
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Old 11-02-2010, 06:15   #44
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I heard an interview on npr of a company that is researching solar panels that convert water to hydrogen directly for fuel cells thus solving the electricity/ battery storage problems. If water could be collected from hydrogen use that would solve a bunch of problems at once. Electric drive from sun, no batteries,water as by product.
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Old 11-02-2010, 07:04   #45
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Yes - any country with a lot of sunlight and salty water handy should be able to produce hydrogen by simple electrolysis. Fresh water (by using sunlight to boil salty water and cooling the vapour) should be possible as well.

In Seville in Spain they use sunlight to boil water to steam which then drives a turbine to make electricity. The technology exists and is proven. Some willpower to make it work is all that is needed.

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