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Self Contained Oxygen Extraction Underwater Breathing Apparatus

S.C.O.E.U.B.A. The recent extraction of three of my wisdom teeth, (I don't recomend the experience), prompted the tiniest kernel of an idea which I don't have the knowledge to take futher than an inkling.
 
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The dentist gave me a plastic tipped syringe to squirt salt water into the holes to dislodge food particles.
By trying to fill the syringe too quickly the negative pressure boiled the gasses from the water and the syringe would fill with air.

I was thinking that if Hydrogen, {ammended from CO2}, were scrubbed from the mix before the gasses recondensed then oxygen could be added to a scuba or re-breather system while still submerged letting divers stay down for much longer periods of time.


Like-a-Fish Technologies http://www.likeafish.biz/
[MechE, Sep 28 2008]

Piezo flipp..er, fins. http://www.freepate...ne.com/5494468.html
[2 fries shy of a happy meal, Sep 29 2008]

Human Oxygen requirements http://www.newton.d.../eng99/eng99210.htm
?not confirmed [Ling, Oct 01 2008]

Dissolved air in water http://www.engineer...ty-water-d_639.html
[Ling, Oct 01 2008]

[link]






       more probable the negative pressure undissolved the gases.
FlyingToaster, Sep 28 2008
  

       'Undissolved' is a far less accurate description for low pressure gas extraction than 'boiling', in my opinion. That being said, you probably just had the tip of your syringe out of the brine for a minute, sucking in a little bit of air in the process. Very little oxygen soluble in water at ATP. Also, CO2 aids breathing at small percentages so scrubbing might not be necessary, simplifying this dubious process.[+/-]
daseva, Sep 28 2008
  

       Heavily pre-heated in science fiction, currently under development in real life. Do a search for artificial gills.
MechE, Sep 28 2008
  

       Ah, thank you. I searched quite a bit for negative pressure oxygen extraction but only found sites having to do with pulmonary edema. I had assumed that any attempts to extract air from water would be done through electrolysis.
<hmmm makes note to search for piezo flippers>
  

       <later edit
[link]>
  

       Currently the time a diver spends underwater is limited by the CO2 scrubber, not the amount of air they can carry.   

       Rebreathers can last up to 6hrs, open circuit (typical SCUBA units) can last up to 2hrs without too much additional training (ie not too deep, large twin-set, not excessive use of stage bottles).   

       Any environment that would require a diver to stay down longer would be very deep (eg offshore saturation diving, ~200m) or poor access (wreck and caves) and the dissolved oxygen would be very low.   

       [2 fries], Not flippers. Fins.
miasere, Sep 29 2008
  

       It is much more likely that your pull created a pressure drop so much greater than what could be equalized by the nozzle that the seal between the wall and the rubber gasket failed temporarily failed.   

       Has anyone ever considered electrolyzing water to gain the requisite breathing water? Too slow, i would bet, on a small scale. <gasp>
ericscottf, Sep 29 2008
  

       Unless your dives were shallow, you''d still have to take along an appropriate inert gas to bulk out the breathing mix - pure oxygen is toxic at relatively low partial pressures.
You could suffer the potentially fatal effects of oxygen toxicity at only five or six metres.
AbsintheWithoutLeave, Sep 29 2008
  

       The partial pressure argument is a good one. But you may find that garden variety scrubbers already take this into account (it is the main reason they reticulate). CO2 is a neccesary component of our breathing. Without significant CO2 pressure (accumulation) on your system the "breathe in" impulse does not trigger. It is quite possible to suffocate in a pure O2 environ, at abnormal pressures. It is debated whether this is due to O2 toxicity at the pressure or lack of the "CO2 breathe impulse." That is my understanding.
4whom, Sep 29 2008
  

       Is an unburnt mix of oxygen and hydrogen breathable?
Voice, Sep 29 2008
  

       //That being said, you probably just had the tip of your syringe out of the brine for a minute, sucking in a little bit of air in the process.//   

       //It is much more likely that your pull created a pressure drop so much greater than what could be equalized by the nozzle that the seal between the wall and the rubber gasket failed temporarily failed.//   

       The entire syringe would fill with gas and unless I pulled too far and popped the plunger out of the tube it would quickly refill with fluid as the pressure equalized.   

       [correction] I meant Hydrogen and not CO2 in the main body of the idea.   

       //Is an unburnt mix of oxygen and hydrogen breathable?// For non-smokers, yes.
coprocephalous, Sep 30 2008
  

       Just the tip.   

       To generate enough oxygen to breathe you would require 8.2kW of energy, plus and additional 0.82kW for every meter you were underwater. Since AA batteries have the highest energy density (as they have the largest market), a litium battery can have up to 3Ahrs, at 1.5V, giving 4.5W. This means you would have to carry 1823 AA batteries plus 183 for each additional metre depth.   

         

       Per minute.
miasere, Sep 30 2008
  

       //Per minute.//
Where does that come from?
Mixed units?
sp. "metre"
AbsintheWithoutLeave, Sep 30 2008
  

       we used to play with the things in school; many advantages over the more common water pistol... so I speak from experience :) he's introducing cavitation, it's not difficult, remember: 14psi.
FlyingToaster, Sep 30 2008
  

       Water contains 0.045g of oxygen per kg, at 25C, 1 bar gauge pressure. It's 3 x more at 5 bar gauge, or when colder.
A person requires about 3kg O2 per day.
  

       It seems the system would need to process 66 tons of water per day, but this is less than 1L per second.
Ling, Oct 01 2008
  

       Is an oxygen sink (making the oxygen come to you) different from processing fixed units of water (gold in rock)?
wjt, Oct 01 2008
  

       //Not trying to be difficult, but that's the way it is//
So, you're just effortlessly difficult, [ub]? <gdr>
coprocephalous, Oct 01 2008
  

       Sorry [AWL], breathing rate is roughly 20-25l/min. As 1 mol of a gas is 24l, you need enough energy to produce 1 mol of gas every minute.
miasere, Oct 01 2008
  

       1 mol is 22.4l at STP.
I breathe about 16 litres per minute (surface equivalent).
However, of those 16 litres, only about three and a half are actually oxygen.
AbsintheWithoutLeave, Oct 01 2008
  

       1 mol is 22.4 l at 0 degrees C, 24l at 24 degrees C, room temperature. While water is colder than air we can assume that people will need to breathe about 1 mol per minute.   

       Breathing rate is irrispective of concentration. If you are thinking of using the system as closed circuit (rebreather) then the fact you can extract oxygen from water is irrelevant as the scrubber (sofnolime) only lasts 6hrs max. With open circuit breathing rate should always be assumed to be under slight stress as the worst case scenario must be taken into account. If you only assume 16l then if you have to do heavy work then you will not have enough to breathe.
miasere, Oct 01 2008
  

       Maybe the most efficient way would be to pull a vacuum on a loooong horizontal cylinder full of water. The piston could be mounted in the end, so the force would be smaller (like a bicycle pump). Horizontal orientation makes sure the pressure in the water is mostly the same. When the air bubbles off, collect it, rinse and repeat.
Ling, Oct 01 2008
  

       //While water is colder than air //
Not necessarily; only last weekend I was diving in 20 degree fresh water, but the air temperature was only 11 or 12.
It /felt/ colder, but that's because water is a better conductor of heat than air.

Yes, one may have to breathe a mole of /gas/ per minute on the surface, but only 21% of that gas needs to be oxygen, so you only need to extract a mole of oxygen every five minutes or so, not one mole per minute.
AbsintheWithoutLeave, Oct 01 2008
  

       //The only way to be certain it's cavitation is to completely immerse the syringe, to establish it's not air from another inlet point. Not trying to be difficult, but that's the way it is.//   

       Ok, I submerged the syringe, filled it with water, tapped the syringe under water as the last air bubbles were expelled and then tried the process again while the syringe was submerged.
The cylinder still filled almost completely with gas before the water bubbled its way into the syringe. I held the plunger taut and did not let it snap back from the end of the cylinder.
  

       So I guess my question is;
If held as a gas at this pressure, would hydrogen still be less dense than, and also separate from oxygen given Earths gravitational pull?
  

       Cool links. Thanks.   

       //At this pressure, would hydrogen still be less dense than, and also separate from oxygen given Earths gravitational pull? //   

       At any pressure hydrogen is less dense than other gasses. More specifically it has a lower partial pressure, relative to the other gasses, that all sum to the pressure. Not likely to seperate, however.
4whom, Oct 02 2008
  

       [2_fries] your last question leaves me thinking you're still confusing dissolved gases in water with the bonded oxygen in the water molecule. Not the same thing at all.   

       It's feasible you could extract a tiny amount of dissolved oxygen by hand pressure. It is utterly impossible that you could be breaking the bonds of the H2O molecule to create gaseous H2 and O2. That's achieved by electrolysis, and requires metric buttloads more energy input. Completely different process.
BunsenHoneydew, Oct 02 2008
  

       Your not doing the syringe test in the kitchen sink beside your old microwave while heating up a coffee, with your cellphone is ring in your pocket , in your house that's situated in close proximity to high tension power lines ? ;-)
wjt, Oct 02 2008
  

       I "had" assumed that the two gasses would separate. Though all I have done is create water vapor of course.   

       Cavitation is interesting and I wonder if this could be adapted to do something besides eroding propeller blades.   

       Would it be possible to turn a burnable liquid directly into a vapor using this principal to increase combustability? I mean we turn gasoline into a mist with injectors now right? Would a vapor not burn more efficiently and increase milage?   

       We do. Liquids rarely burn, especially hydrocarbons. What burns is the vapour of the liquid. Diesel needs to be heated until it starts to vapourise before it will ignite. Petrol (Gasoline) is more volatile and will vapourise itself, hence its explosivness.
miasere, Oct 06 2008
  

       Water is not a fuel, it's an ash. It is what is left over after you burn hydrogen. There's no chemical energy hidden in water waiting to explode, like there is in hydrocarbon fuels.
BunsenHoneydew, Oct 07 2008
  
      
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