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temp glazing and cheap solar collector - Page 6

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Posted by Jeff on December 6, 2006, 6:44 pm
 
sylvan butler wrote:

than

    You may wish to back up to the point that I had asked. And that was,
since I'm using polyethelene can I read through that and find the hot
and cold spots. The answer appears to be yes, because of the relative
transparency. The actual temperature is immaterial for my purposes, and
since this does not work for other glazing, I'm in luck.

   Without actual readings from the absorber you

   Gary has a few things going that will lower stagnation temps in
general. The collector is vertical and will recieve less sun when the
the sun is higher in the summer, and that he is using single wall
glazing. There've been quite a few of these "matrix" type collectors
made and stag temps never seem to be a serious problem, as they may be
in other types and orientations.

I'm not surprised he was published. Gary's got it going on! And that pic
makes the perfect cover.

   Cheers,
Jeff




Posted by sylvan butler on December 7, 2006, 10:13 pm
 

than

Regardless of your question or intent, _I_ was responding to _Gary's_
comment (quoted above) about Acrylic, Polycarbonate, Vinyl and
Polyethylene glazing and trying to determine if it was the glazing
temperature or the absorber temperature based on a comparison to the
temperature of an unglazed absorber.


sdb

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Posted by SJC on December 5, 2006, 12:14 am
 

anyway).

absorber?

  What this means to me is that the polyethylene is the same temperature as the
aluminum and is not an insulator. That means that your loses are about as high
as having no glazing at all. A pretty inefficient configuration, I would say.



Posted by Gary on December 5, 2006, 3:55 am
 SJC wrote:

Well, I don't think so.  I should have said a bit more about how I took the
measurements.  I let the painted alum come up to temperature with no glazing.  I
would the then take the various glazing samples (which were out of the sun, and
at garage temperature of about 60F), and quickly place the glazing sample over
the alum and take the temperature measurement with the IR scanner fast enough to
not let the glazing change temperature.   I think that in all cases the
temperature of the glazing samples was about 60F when the temperature
measurement was taken.  I think that since the polyethylene is transparent to
IR, the IR temperature scanner sees through it to alum underneath.

Gary




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Posted by Jeff on December 5, 2006, 8:31 am
 Gary wrote:

   Thanks. (I've read through the thread)

   That makes a lot of sense and also answers my unasked question about
Vinyl. It would appear the acrylic actually might be the best material,
stagnation temps aside as it would have the lowest reradiation loss.

   I made a quick trip up to Cleveland and back to get a friend (1400
miles) (fixed car on both ends and fixed brothers car and friends
equipment) and it has completely knocked me out. Almost unable to move.
Current thinking is to oversize the plenum. Perhaps 16" by 8" and to
oversize the back end of the collector. That would guarantee the
pressure drop across the screen and through the orfices would be dominant.

  Went out to the local community organic store and was surprised not to
find "Mother Earth News".

   Cheers,
Jeff


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