Half a croissant, on a plate, with a sign in front of it saying '50c'
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Keep the warmth where you want it .....
  [vote for,

"Hot air rises" - and this can be a real problem in some places; in stairwells, high rooms and atria, the heat ends up near the ceiling, doing no good to anyone.

The answer to this perennial problem is a DenseAir heating machine. It sucks in normal atmospheric air, and separates it by a fractional distillation or gas centrifuge process into oxygen, nitrogen and argon.

The Nitrogen we can do without; it's the argon we're after. Argon is substantially heavier (even when warm) than normal air - so, using evergy extracted from outside, the argon and oxygen are re-evaporated (heat pumping) recovering energy from the environment. This oxygen/argon mix is further heated to the desired temperature by waste heat from the motors or engines which drive the compressors or centrifuges, thus recycling more energy.

Cool nitrogen is expelled through high-level vents; warm oxygen/argon mix is blown out (gently) at floor level. The result is that the humans wander round in a layer of warmer, slightly denser, but still perfectly breathable odourless gas indistinguishable from normal air. Because you're only heating the bottom 3 metres of your structrure, much less energy is needed.

8th of 7, Nov 18 2002


       I always wondered why air didn't naturally fractionate. I have difficulty imagining that random motion is enough to keep it all mixed.   

       If the reason air is so well mixed is because the atoms travel long distances between collisions then your carefully separated air will mix quickly.   

       If the distance between collisions is short then why doesn't air naturally fractionate?
st3f, Nov 18 2002

       As regards natural fractionation, I wonder if this might not occur over large still bodies of water, like a lake. Different gasses have different solubilities in water. One could see how the lake might locally deplete the air of nitrogen and enrich it (relatively speaking) with less-soluble argon.
bungston, Nov 18 2002

       Fractional separation actually does occur in water; that's how Norsk Hydro get their heavy water ..... but it's a very slow, inefficient process.   

       [Nick@nite] Because that would be a nutcracker to crack a nut. I prefer sledgehammers - or steam hammers - or shaped charges ......
8th of 7, Nov 18 2002

       In still, closed areas (like caves), CO2 (which is heavier than O2 or N2) will sometimes settle out and form a layer. This can create a hazard for explorers. So it does happen, but in anything like a building with doors opening and people moving about, it probably wouldn't be more than a minute before it was all mixed up again.   

       In any case, the cost of separating out argon (which is a very small fraction of the air) seems likely to render this an uneconomical but interesting idea. Perhaps you'd do better to fill the top of your building with some other lighter-than-air inert gas. Helium's a bit expensive, hydrogen's not exactly inert, but maybe we could come up with something.   

       Of course you still have the problem that someone unwittingly gets on a ladder to change a light bulb, enters the oxygen-free zone, passes out, falls off the ladder, and...
egnor, Nov 18 2002

       If you had a Van de Graph generator zipping round on a monorail above the diners heads, it could zap them on the pate with a mini thor bolt thus increasing internal body temperature organically. This is the greenest solution I need hardly add.
Admiral Hackbar, Nov 18 2002

       Employ microwave radiation. But be sure and leave your pacemaker at home.
RayfordSteele, Nov 18 2002

       Could you set up an artificial convection current in the lower half of the atrium? You could blow air in horizontally to deflect the rising hot air.
st3f, Nov 19 2002

       You could empoy mime artists to rush round galvanizing people, maybe rub their shoulders, paint the walls pink, generally create the illusion of warmth?
General Washington, Nov 19 2002

       [AH] with the added benefit of extra ozone to plug that pesky hole.   

       Alternative solution: Put the floors on a rotating platform lift thingy and move them to the position of optimum temperature.
egbert, Nov 19 2002


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