Using compression/expansion (pressure differential).

or, similar to the hot side of an air conditioning unit.

No fire needed, just the ability to compress the liquid.

Seems I was inspired by an old junkyard wars tv episode.

Just something to consider.

yeah, it's the "pressure-temperature" curve. One of the reasons people use Pressure Cookers: boil at lower temps.

How this will help in real life, I have no idea.

Could one put water in a pressure cooker, set that on the fire for a while, and have "safe" water???

I think the pertinent fact is the water would still need to boil. The only thing increasing pressure does is increase the temperature at which water boils. NOTE: I probably mixed this up in my original post. This means that the pressure cooker would raise the boiling point (thus allowing cooking at a higher pressure WITHOUT boiling water off).

"Maximum vaporization occurs at the boiling point, 100°C (212 °F) at 1 atmosphere. Conversely, the vapor pressure of water, that is, the pressure of the vapor in equilibrium with the liquid, is 760 mm Hg at 100 °C. If the atmospheric pressure is reduced to say, 525.8 mm Hg, as would be the case if the same kettle is boiled on the top of a mountain, the boiling point will be reduced by several degrees to 90 °C (194 °F). The reason: at this temperature the vapor pressure of water is 525.8 mm Hg."

http://www.unesco.org/webworld/ramp/html/r8707e/r8707e06.htm

Sorry about the earlier typo: I wasn't reading as thoroughly as I should have (studying at the time). Notice also how little the boiling point changes, even with rather significant changes in pressure.

Sure, if you reduce the pressure enough, water will boil at room temperature. But if you are talking about cooking or purifying water, it won't help. It is the temperature that matters for cooking or purifying (killing bacteria). The actual boiling or vaporization point of water has nothing to do with it. On the opposite end of the scale, raising pressure raises the temperature at which water boils, which is what a pressure cooker does. At sea level pressure, you can't get water hotter than 212 degrees farenheit, but by increasing the pressure, you can get water much hotter which is why a pressure cooker can cook foods faster, or break down foods that need a higher temperature than the normal boiling point of water.

No, not lowering the pressure, but raising it, dramatically. If you raise the pressure on a container 2/3 full of water, it should eventually reach temps above 100 C (212 F). Think like with a fire piston.

Water is incompressible so you can't raise its temperature by compressing it. You could raise the temperature of air and transfer the heat to the water, but...

To raise the temperature of 1 gallon of water from room temp to boiling takes over 1000 BTU. That's 778,000 ft-lbs. So if you weigh 200 lbs, you can jump off a ~4000 ft cliff and land on the piston - boiling water!

(My apologies for the non-SI units)

Actually, it does NOT need to boil. It needs to reach around 200 degrees, which kills everything. If it were in a strong enough pressure vessel, it might not boil until 220 or so.

Boiling is just any easy way to see if it the water is pasteurized yet.

200F kills close to everything, but not quite. There are spore-forming bacteria (Bacillus and Clostridium species) that are heat resistant and can withstand 200F and still be viable. Our steam autoclaves operate at 250F under 15 psi, at this temperature and pressure, sterilization is usually a 15 minute process, although depending upon the type of load and how it is packed into the autoclave, sterilization times may be extended to as much as 1 hour.

Pete

I think they were more referring to the 212 degree heat thing as being destructive to bacteria/viruses that are most often considered harmful to humans and take residence in water.

The ones you listed are mostly related to food poisoning (of all things) and are more of a reason to cook your food thoroughly than in relation of trying to purify water. Here's a list (per wikipedia)

Bacillus anthracis is a Gram-positive, facultatively anaerobic, rod-shaped bacterium of the genus Bacillus. An endospore forming bacterium, B. anthracis is a natural soil-dwelling organism, as well as the causative agent of anthrax.

Bacillus cereus is an endemic, soil-dwelling, Gram-positive, rod shaped, beta hemolytic bacteria that causes foodborne illness.

Bacillus coagulans is a species of lactic acid forming Bacillus bacteria, which can contaminate canned food and gives it a flat sour taste.

Clostridium includes common free-living bacteria as well as important pathogens.[2] There are four main species responsible for disease in humans:

C. botulinum, an organism producing a toxin in food that causes botulism.[3]
C. difficile, which can overgrow other bacteria in the gut during antibiotic therapy, can cause pseudomembranous colitis.[4]
C. perfringens, causes a wide range of symptoms, from food poisoning to gas gangrene. Also responsible for enterotoxemia (also known as "overeating disease" or "pulpy kidney disease") in sheep and goats.[5]
C. tetani, the causative organism of tetanus (lockjaw).[6]

Just trying to make sure this doesn't cause confusion for some.
Good info nonetheless

Menawa wrote: "Sure, if you reduce the pressure enough, water will boil at room temperature."

That's right. And the water that flashes into vapour should be extremely pure.

So how do we capture that vapour? I see some sort of crazy hand-cranked piston setup, with raw water in one vessel and drinking water condensing in another.

Seems like a lot more work than filtering, though.

BENJAMMIN--
is this what you were thinking of???
this is a homemade "fixture" for removing dents from Sigg
bottles..it's the cap with a bike valve glued in..



you put it on the bottle and pump up with a HAND PUMP and
the dents pop out..no it will no blow up..the gasket will
leak long before the bottle will fail..i get it up to 80PSI
with no problem and the Forest Service has tested the bottles
for use in aircraft and they fail only at very high PSI..
ANYWAY---could you crush the life out of the nastys in
the water by putting them under just the pressure you
could come up with in a home made gizmo ??? i think that
was the crux of Benjammin's question..



ACTION PHOTO...and please no "nannyism's" on this..
if you use a HAND PUMP the pressure will come up slow
enough that the cap gasket will leak and the bottle
will not blow up and cause you and your family,frends
and the health care system unnessary grief and expense..
thank you....

So I'm wandering, if you had a bike pump and pressurized it, at what pressure would you need to get it up to 212 degree and how long would you have to hold it to kill viruses? I would think the heat in the tank would convect out to the open air quickly once you came up to the temp/pressure not giving enough time to kill pathogens.That would probably be where vacuum jacket would help, but would crush under pressure. Force=Area(in Square inches)X Pressure. It would be interesting if you have a laser thermometer and measured the outside wall as you brought pressure up, and looked at how fast it dissipated.

CANOEDOGS - Not to nanny you here - and you may be sure that they'll never blow up - BUT *very* cheap insurance would be to mostly fill the bottle with water. Bonus is that you won't have to pump as many strokes.

Gotta agree with thseng--liquids are, for all practical purposes, incompressible. That's how we can take advantage of hydraulics.

But, an interesting idea. Benjammin, please don't go and hurt yourself with that fire piston. Seriously--you won't be boiling any water with it!

THSENG..
these are photos i took for another campers site a few
years ago..i tryed filling with water first but could only
pump a few times before it became to hard to do..then i tryed
them dry and it was pumping up a bike tire and the dents
"crinked" out..i also did stuff like put a wet rug over the
bottle for a "blast mat" but found that was not nessary.

Uhhhhhhhh... A pressure cooker RAISES the boiling temperature so that you can get the temperature of the food or water ABOVE 212F(100C)...
At high altitudes, you have to use a pressure cooker just to make sure that your food reaches a safe temperature, or that your water is sterilized... It is not the boiling that cooks or sterilizes, it is the temperature... And you can not get the temperature of something(in it's liquid state) above it's boiling point. So you have to raise the boiling point to a point where the temperature is high enough to cook or sterilize...

> Pressure Cookers: boil at lower temps.
Hmm... . My thought was that water under pressure boils at higher temps. Hence pressure cookers for canning reaching higher temps than 212 to sterilize the food better, quicker, or whatever.

Cooking at high altitude requires different times because water boils at less than 212 degrees, right?

I am pretty sure the pressure alone will not be enough to get water to boil. As someone mentioned, water is incompressible, so putting it under extreme pressure will not do much. We used to test high pressure tube fittings at up to 6000 psi, filled to the top with water, with no noticable change in the temperature. This prevented an potentially deadly explosion, because a if a device was filled with air at that pressure, the expansion of the air would cause a huge BOOM! and probably kill anyone nearby. Filled with water though, it's more of just a small harmless pop because there is much less air volume to expand.

The other factor that needs to be considered is high heat capacity of the water and the amount of time it takes to bring up that pressure. The reason those fire pistons work is because the volume of tinder is very small and they compress the air in a very short amount of time, thereby increasing the pressure and temperature very rapidly. If you try and slowly pressurize it, most of the heat generated will quickly dissapate through the walls of the chamber. You could increase the temperature of the water using the pressure/temperature principle, but the I'm guessing it would be very inefficient. It would probably be the same effect as using water to cool the heatsink fins generated from an air compressor. Water is able to absorb a tremendous amount of heat, which is why it is used in everybodys radiators.

The microbes would be sustained in the droplets of vapor. The only way to do it would be to drop the pressure to the point that they explosively decompress, and if you have the omphy of a vacuum pump, you're not that far into the back country.

*nods* The ones you can't kill by boiling anyway at 1 atmosphere. But what survives above 170 but dies below 212?

I ask becuase IIRC commercial pasteurization usually just has to worry about hitting 170, but it's been a while since I worked in the bottling plant.

"Boiling water without a heat source... Using compression/
expansion (pressure differential)... or, similar to the hot side of an air conditioning unit. No fire needed, just the ability to compress the liquid."

I'm assuming that this was just a rhetorical, toss-it-out-there idea. After all, which are you most likely to be able to do in a survival situation, dredge up debris to make this iffy contraption, or make a fire with almost anything else, by comparison?

Sue

In all honesty, I think you'd find that the air you were compressing was getting kinda liquidy first. And liquid hydrogen and oxygen will kill anything- either from the cold or from the kaboom.

Hey, some guys have skills, they can make you a shopping mall with a q-tip and a pocketknife...

You need to watch more MacGyver. I bet he could do it with a paperclip and turkey baster and of course, duct tape.

I was Googling for something and I stumbled across this invention that is kind of similar in concept. I don't know much about it, but I just thought I'd throw the idea out there if anyone was interested in it.

It's called the Hydrosonic Pump, invented by a heating engineer out in Georgia. Basically, it heats water through turbulence or shock waves. Imagine a single car engine cylinder and piston head. Scale it up bigger and turn things on their side. Attach a motor to the piston head so that it spins in place (not travels back and forth). The sides of the piston head have a bunch of holes, and there's a bit of a gap between the piston (actually, I guess I should call it a rotor) and the cylinder wall. Fill the cylinder with water and start spinning the rotor. The caviation or turbulence generates heat, which then heats the water up. Even makes steam.

Here's the kicker, which makes the Hydrosonic Pump controversial--it apparently generates more energy than it uses. I know, I know, Law of Conservation of Energy and all, but I'm not sure if anyone has been able to discredit that claim. There are a few actual commercial installations running this thing, mostly for generating steam heat, and apparently their energy bills have all gone down.

Anyway, putting aside the energy issue, this thing really does heat up water without any combustion involved. OK, so out in the bush, you could carry one of those old manual egg beaters/mixers, with the hand crank, and crank that thing really, really fast, and then you'd be able to boil that river water and make it safe to drink...well, after you've recovered from all that faster-than-humanly-possible cranking.

All I'm going to say is, I hope the inventor got the patent before going public.

Oh, if anyone is interested in watching a video about the Hydrosonic Pump, I stumbled across it by watching this video. The video has several segments about interesting--unbelievable, actually--energy-related inventions.

Note that the video is mislabled. I was looking for a video on the Federal Reserve that someone suggested to me, and I stumbled on this video instead. Very interesting if you like science shows.

Arney, you might want to hold off on buying stock. Let's see their electric bill for $0 first.

What they have there is no better than, and much more expensive than, the $5 resistive heating element in standard electric water heater. Which, by the way, is and always was 100% efficient in converting electrical energy to heat.

If, and that's a big "if", they are measuring the energy of the steam correctly, most likely they are making what Don Lancaster calls "Freshman EE Student Lab Mistake #1" - Incorrectly measuring AC electical power input.

Why don't they just route the steam back to a turbine which turns the pump. Spin the whole thing up with the electric motor, then pull the plug - it should keep running, right? C'mon guys, if you won't bother with the science, just convince all us skeptics by doing a simple demonstration.

Ditto for the other "inventions" in that video. Any time you hear that they are "pulsing" the electric current, it is a dead giveaway. People, even "scientists" invariably under-measure the true power in pulsed current.

Oh, and by the way - Water is not a fuel - its an ASH.