Posted by Duane C. Johnson on December 10, 2003, 8:11 pm
I just posted my drawing of a press beading tool. See:
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Posted by Bert Menkveld on December 11, 2003, 12:52 pm
I dealt with this problem in designing a solar collector absorber. I
settled on using 1/16" thick alumininum (0.063") and a pipe spacing of 8",
which I figured gives a maximum temperature rise (of the collector surface
mid-way between pipes compared to the pipe) of about 15C at the maximum
insolation of 1000W/m^2.
I found the 0.063" aluminum locally available for under Can$ / ft^2 (about
US$ / ft^2) in 4 x 8 ft sheets.
Posted by <farview on December 13, 2003, 3:27 am
"Bert Menkveld" <bertATreentronicsDOTcom> wrote in message
Did you form the 1/16" Al in any way? Probably have to form a groove with a
That is a good price. You must be near big distributors near the east
coast. They gig us pretty hard on freight to get stuff here to SW Colorado.
Posted by Bert Menkveld on December 16, 2003, 3:55 pm
No, I just used it flat. I looked around for quite a while for a good
thermally conductive "goo" to thermally bond the copper tubing to the flat
aluminum sheet, but found this type of thermal cement to be available only
in industrial quantities and pricing. I discovered that silicone caulking
actually has fairly good thermal conductivitiy, so I used that between the
copper tubing and the aluminum sheet, holding it together with simple bits
of twisted copper wire run through small holes in the aluminum plate.
Though I have not yet attempted any measurements of the temperature
difference between the tubing and the plate, theory suggest the temperature
drop is reasonable, and practice shows that the panel works "OK". (How's
that for a scientific evalution? :)
I found a couple of local metal shops that had this stuff in stock, so I
didn't specifically pay for shipping (just went and picked it up).
Posted by John Hall on December 16, 2003, 7:05 pm
On Tue, 16 Dec 2003 10:55:49 -0500, "Bert Menkveld"
I'm looking into making some solar collectors (I hope I got the
correct terminology - I get confused between panels and collectors)
for DHW preheat. I'm wary of using dis-similar metals because of
different coefficients of linear expansion, causing the copper pipe to
move relative to the aluminium sheet. This would occur at least daily,
and might cause the pipe to wear through. Also, electro-chemical
effects causing corrosion etc.
Do these cause problems in practice?
Cochrane, Alberta, Canada.
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