Posted by Sid on July 6, 2004, 6:48 pm
It would also bounce the radiation (long wavelength) from the radiator back,
preventing the cooling effect.
One possible way of looking at the idea of using reflectors to cool is this.
A flat plate insulated and silvered on the bottom is only radiating energy
from half of its' surface area. By using reflectors, you can double it,
along with the radiative cooling effect.
Perhaps as an experiment you could fill some copper tubes with warm water
and make use of reflectors with one of them, and record how quickly their
temperatures drop, and how low their temperatures go. Should be fairly quick
and easy to do.
Here's a though. Since the radiation is long wavelength, the reflectors need
not be shiny or opaque. Glass could do the trick!
Posted by daestrom on July 6, 2004, 8:56 pm
What you're saying is true, *if* the reflector blocks the line-of-sight
between the collector and some warm body here on Earth. But I was thinking
of folding any such reflector down so that there is a wider arc of *sky*
exposed to the collector. If the reflector is just between the collector
and some portion of the sky, then the radiant flux from the reflector *must*
be higher than the portion of the sky it obscures. And in that case, no
reflector is better.
But yes, if instead it blocks radiant energy from some earth bound objects,
then it would improve the cooling.
Posted by N. Thornton on July 6, 2004, 10:17 pm
Lets see... objects on earth have temp determined by conduction and
radiation to and from other objects around them, including air. If we
vacuum insulate something, there is very little conduction, and temp
is determined by the equilibrium of radiated heat to and from the
object. Now if we add sky pointing reflectors all around our insulated
object, the object still radiates but the sky radiates very little
back. Dose this mean that oevr time this object would fall well below
earth air temp?