Could body-warmed air be used to heat head and neck skin?

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Offline thedoc

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Paul asked the Naked Scientists:
   You are standing at a bus stop at 0530 in a cool 4 degrees with your beanie down over your ears to keep the warm. If you were wearing a singlet with vertical tubes imbedded in the singlet, the air in the tubes would be heated by your body heat. Hot air rises, comes out at your neck, rises and keeps your nose and cheeks warm. How's that for an invention? I was going to suggest nanotubes to be more "scientific" but the air might now rise so readily, considering the size of the diameter of the nanotubes and the size or O2 or Nitrogen,etc.

What do you think?
« Last Edit: 28/07/2015 01:50:01 by _system »


Offline alancalverd

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Re: Could body-warmed air be used to heat head and neck skin?
« Reply #1 on: 28/07/2015 10:38:37 »
Natural air convection requires about a minimum of 1 cm diameter, so the tubes will need to be wider than the airgap in a double glazed window (they are designed to the maximum width that won't support convection).

You could use a pump, but your heart does a very good job of circulating warm  blood (a much better heat transfer fluid than air) to where it's needed.

And here's the downside: the capillaries in your extremities shut down progressively in the cold, to conserve heat where it's needed - in the brain, heart and digestive system. If you start moving heat away from the core to heat the less important bits, you will become hypothermic remarkably quickly. It's a pleasant death, as the warm extremities, which carry the nerves that make you conscious of the cold, will feel comfortable whilst you lose consciousness as the bridge and engine room shut down. But presumably you want to go to work rather than die in the street, so just enjoy the sensation of a ship on full alert! 
helping to stem the tide of ignorance