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Thermal flow in aluminum

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Posted by amdx on February 22, 2009, 3:27 pm
I'm building a solar collector the uses aluminum to transfer heat to a 1/2"
copper pipe.
The original design uses 0.018" aluminum, I have access to 0.010" scrap.
Will the 0.010" aluminum move the heat received to the pipe at an efficient
I don't know what info is needed to calculate the answer, but I'll give you
some data.

Intensity of the sun 317BTU/sqft-hr or 1000watts/m^2
Glazing material reduces the intensity about 15%.
Heat must flow 3 inches in 0.010" alum to be transfered to copper pipe
Average temp of water in collector 110*F  ( somewhat of a guess)
Water flow is about 0.03 GPM per sqft of collector.

See the design copper/alum connection about 1/2 way down on this page.


Posted by Puppet_Sock on February 22, 2009, 4:31 pm

Take a chunk of your Aluminum about a foot long. Staple
it to some sample wood in a similar way to how your system
is supposed to work, but leave an overhanging end.

Put that end in a heat source. Select a heat source that
won't degrade the Aluminum. A blow torch is too hot.
If you select something hot enough to remove the oxide
coating on the Aluminum, you won't like the result.

Carefully determine how far from the heat source the Aluminum
gets hot. Watch out for burnt fingers.

Posted by Jeff on February 22, 2009, 9:14 pm
 amdx wrote:


  You'll need closer spacing of the risers if you want to keep
efficiency in the same ballpark. Thicker aluminum, or multiple layers is
probably going to be cheaper.


Posted by Joesepi on February 24, 2009, 2:13 am
 The contact heat transfer will probably be more critical than the aluminum

Posted by amdx on February 24, 2009, 12:33 pm

  Yes, I'm sure that could be a bottleneck to heat removal. The collector
designer uses silicone because it is so much better than air and its high
temperature characteristics. I have a couple of emails out to thermal mastic
manufacterers to get some additional details, if it's cost effective I would
use it.

  My question still remains, "Will the 0.010" aluminum move the heat
received to the pipe at an
 efficient rate."
 I couldn't get the program listed by Jeff to do anything but tell me I had
an error.

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