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Posted by Anti-Spam on August 17, 2008, 7:05 am
I did post this in an engineering group, got no takers, so bought my
questions here, sorry for the cross post. Would like some help please,
I am not a professional mechanical engineer, but I/we can put stuff
together. We are looking to start a small scale manufacturing

Would like peoples advise please, I am putting a design together for
Solar Water Heating Panels. I was going to use off-the shelf copper
tubing for the water matrix, but I needed to fill in the gaps between
the tubes with some sort of heat collecting/transmitting metal to
transmit all the heat into the tubes. It would be nice if I could use
pressed aluminum plates which have a channel stamped into them, that
simple clip onto the copper tubes. Ideally some sort of thermal
conductive adhesive would bond the two together to give maximum heat
transfer. Anybody think of any problems with that idea? and any ideas
as to a supplier in Europe of the adhesive?

As far as the water matrix is concerned, I was going to use 28mm
copper tubes for the upper and lower feed/return tubes, and 12mm
copper tubes as the vertical heat collecting tubes. Not been able to
find a sensibly priced, off the shelf T-pieces 28-12-28, so will most
probably just drill the 28mm tubes and poke the 12mm tubes into the
holes and braze the tubes in place, would anybody care to give their
opinion on that idea please.

For the carcases of the panels, I was going to get a price on having
an aluminium extrusion tool made, so I could make the frames out of
extruded aluminimum, I have no idea what something like that would
cost, can anybody give me an idea of price please?

Lastly, if I did go down the route of using aluminum extrusion, what
sort of machine would I need to buy, that could cut the relatively
delicate extrusion into nice mitred corners?

Thanking you in anticipation.
Mark in Spain

Posted by Jeff on August 17, 2008, 5:21 pm
Anti-Spam wrote:


  Has a nice design program.

  Roughly thicker plates mean you can get by with wider spacing between
the tubes. I made mine out of aluminum flashing as it is so cheap, but
used more than one layer.

http://builditsolar.com  has some jigs on bending the plates and a lot of
great resources and articles.

   You may also wish to just buy preassembled absorbers and just make
the box. This is an extremely time consuming process!

   I smeared a little heat sink compound on the pipes and rivited the
back channel to  the front plate. I used a bit of silicone to help bond
the plates. Some have suggested attaching with just silicone caulk and
if you've ever done a 1000 rivets you can see the beauty of that! I
don't believe that the fin to tube bond is as important as the
properties of the fin itself as there is a lot of contact area.

   You may wish to search this groups archives. Solar Mike in NZ as well
as others have given a lot of advice to me while I was building mine.

   That's fine. I used silver solder. You'll need tight holes and it is
a bit difficult to drill them. I had best luck with a step bit as my
drill press had a bit of chatter.

Plywood with a good grade of paint should work. Insulate with
polyisocyanurate sheets. You can cover the plywood with aluminum if you

   You have a great location for solar!


Posted by Anti-Spam on August 18, 2008, 6:48 am

Thanks Jeff for your time. I am going to make some prototypes using
wood frames to get started, so I can test various tube size options.

Posted by renewable_sources on August 18, 2008, 1:56 pm
To bond your tube to the flat plate try a mix of Epoxy resin with
powdered aluminum and carbon for color ( or grind up some graphite or
aquarium filter charcoal) use enough to make a filet on both sides of
the tube.  Gel type epoxy resin is best to prevent run off. It should
be a thick paste in consistency. Heat transfer is provided by the
powdered aluminum.

Posted by Anti-Spam on August 18, 2008, 7:11 pm
 On 18 Aug 2008 08:56:05 -0500, renewable_sources@hotmail.com wrote:

Great Stuff, this is a definite.

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