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followup regarding a thermosiphon panel - Page 2

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Posted by Gary on November 2, 2006, 2:23 am
Tater wrote:


Thats really puzzling.

So, there must be some air moving through the collector?

I guess you could see if someone has the corrugated PVC glazing -- this is not a
good long term choice, as it does not have good temperature capability, and
degrades faster, but it would be OK just to test.  Its significantly cheaper
than the SunTuf polycarbonate -- maybe $.7 per sqft?

6 ft should still be OK.

And, your airflow path goes under the bottom of the absorber shelf, and then
turns up next to the glazing, then through the absorber screens, and exits on
the north side of the collector up high?

The exit vent area should be at least half the cross section area, and the inlet
vent area should also be at least half.  More is better.

If you follow all the rules, then this implies:

Ainlet = Aoutlet = (h)(1/15)(1/2)  sqft per foot of collector width

So, for an 8 ft high collector, this would be 0.27 sqft per foot of collector
width, or about 1.1 sqft for a 4 ft wide collector -- with more being better.

I am guessing that the glazing is the most likely cause for the no performance.
The other things might cut the performance back some, but its just really a
puzzle that you are not getting a good temperature rise.


They do work -- honest :)
I went out to the garage today, and it was just getting to 70F downstairs, and a
little warmer up in the storage loft.  The outside high temperature for the day
was 28F -- we are getting an early dose arctic air.

I'd like to hear how this works out.
If you have a digital camera, you might email me some pictures just to see if I
can spot anything.


"Build It Yourself" Solar Projects

Posted by Tater on November 2, 2006, 3:20 am

Gary wrote:

yeah...but it is less than what one would exhale gently

also, I do not have the thermometers in side the panel itself. kind of
hard to do without ripping out the hardware cloth on the top.

like I said, the general design was (almost) exactly like yours. only
difference was the film instead of polycarb. and a 1/2 inch metal foil
inulation board painted black. and........


 Rough calculations from memory made each one nearly full size as cross
sectional area. rough cut openings were approx 4-5" tall, went
completely across the panel, with the exception of the wall studs.

doubt it, you'd see a sheet of nearly white plastic with *something*
black behind it.

I dont doubt that they work, I just wanted to inform some people of my
progress, and let then know that not all panels work right, even if
they are hybrids of two working designs.

the other poster that is heating his hangar, I hope he reads this, If i
can get the garage roasting, I'll siphon some of the heat to the house,
and cut my home heating fuel costs. thats a next year project, pending
sucess of this.

Posted by SJC on November 2, 2006, 4:51 am

  One thing I read about insulation is that you do not want contact.
The foil is in contact with the foam and this can reduce performance.


and a


Posted by Tater on November 2, 2006, 9:04 pm
SJC wrote:

of the insulation? yes. in another thread i explained why i put the
insulation in, and has nothing to do with insulating, so it's a moot

Posted by Jeff on November 2, 2006, 9:26 pm
 Tater wrote:

   This caught my eye before but I didn't weigh in. I'm not sure exactly
how you have the insulation, but... painting the foil black negates the
radiant barrier aspect. Probably better to have it just bounce the light
back on the screens.

   Your main problem is elsewhere, and only you will be able to go in
there and figure it out.


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