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Re: Trombe wall efficiency



Steve Paschke <steve_paschke@msmgate.mrg.uswest.com> wrote:

>> Nick Pine <nick@vu-vlsi.ee.vill.edu> wrote:
 
>> Here's a small picture, a view from the East, say:
 
   ---------------       ^
   132F <=O= <|   |      up        32F                    311 Btu/hr/ft^2
          |  <| ^ |                                 < --- Sun
      |   | ^<|   |<-Polycarbonate plastic
      |   |  <| ^ |
    house | ^<|<--|--80% shadecloth
     16'  z   z   z i                          South
          |  <| ^ |
      |   |<--|---|--Original house wall                  (clear enough? :-)
          | _<| ^ |
    68F ==I====>  |
   -------------------------------------------
          |  3"   |
 
>Wouldn't black painted metal be better than shadecloth at absorbing heat
>and radiating the heat absorbed?

The idea here is that the cool air rises up through the passage between
the glazing and the shadecloth, moves ***through*** the shadecloth,
from right to left, becoming warmed in the process, as in the Conserval
wall, and goes back into the house at the top. If the black-painted metal
had no holes in it, it would probably not work as well as the shadecloth.
If it did, it might work better, like the Conserval wall.

>I've built a unit several years ago with painted beverage cans with mild
>success.  I think that a large heat sink (made from scrap sheet metal)
>would be most effective.

Lots of absorbing surface area is nice, altho it's curious that
in a linear model, it looks like that doesn't matter at all.

Nick


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