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Re: [Hammock Camping] Radiation/absorption question

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  • zippydooda
    Youngblood, you are correct. So, you paint your radiators black, since you want for the heat to get out of them. But, you use a brightly polished teakettle
    Message 1 of 12 , Oct 31, 2004
      Youngblood, you are correct. So, you paint your radiators black,
      since you want for the heat to get out of them. But, you use a
      brightly polished teakettle (or light colored, I guess), because it
      keeps the heat in.

      At night, the outside surface of your peapod (or underquilt) is
      warmer than the surroundings, so you want to try to keep that heat
      in. So, you use a light color or even a reflective cover. If you
      make it dark, you will radiate more heat. You can't soak up heat at
      night with a dark peapod, because heat has to move from hotter to
      colder items (it's a law).

      Like others said, the color of the inside of the bag doesn't matter
      too much, since it's more of a conductive thing going on there. So
      black would be nice since it hides dirt and makes it easier to dry
      your bag in the sun.

      All this radiation stuff works the same with heat flowing the other
      way, too, right? Dark stuff gets hotter in the sun than light
      stuff. The color of a surface (or whether it is rough or polished,
      in the case of metal) influences heat going both in and out.

      Hopefully this makes sense.

      Bill in Houston


      --- In hammockcamping@yahoogroups.com, "Dave Womble" <dpwomble@y...>
      wrote:
      >
      > Ralph,
      >
      > I have this figured differently than you. I believe that darker
      > materials are better at both absorbing and emmitting radiant heat.
      >
      > Youngblood
      >
      > --- In hammockcamping@yahoogroups.com, Ralph Oborn
      <Ralph.oborn@g...>
      > wrote:
      > > You would also want it darker (better absorbing) in the infrared.
      If
      > > it is bright (emmittive) in the IR then even at night you are
      losing
      > > energy (warmth). IR reflectors (foils) will slow it down, unless
      you
      > > are touching it then it is conductive heat transfer.
      > >
      > > Ralph Oborn
      > >
      > >
    • dlfrost_1
      ... camouflage? Probably for both reasons. The hairs of a Polar Bear are almost clear and are hollow. The white appearance comes from the even scattering of
      Message 2 of 12 , Oct 31, 2004
        --- In hammockcamping@yahoogroups.com, "Randy Saylor" <r.saylor@s...>
        wrote:
        > Why are polar bears white? Is it to reduce radiation or give good
        camouflage? Probably for both reasons.

        The hairs of a Polar Bear are almost clear and are hollow. The white
        appearance comes from the even scattering of light and is vital for
        camouflage, as these animals are mainly ambush hunters. Because of
        the internal scattering, the fur is also efficient at absorbing
        infrared warmth from the sun. Their skin is dark back to protect
        against UV light. (This why you see black around the eyes and nose--
        the fur is thinnest there.)

        Doug Frost
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