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Pipescs

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Reply with quote  #11 
Quote:
Good thoughts and I agree. I think that putting the CPVC close enough (maybe a double layer) to eliminate the need for the metal absorber would be a more advantageous approach.


New guy here.

By double layers, do you mean to leave out the flashing and simply put the tubes one to two inchs apart, staggering the two layers of tubes, so that they would be a direct pick up from the sun?

Garage_Hermit

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Reply with quote  #12 
Maybe I am off the wall here, and certainly not wishing to upset centuries of tradition (!) but would it not be far easier (and maybe cheaper...) just to wrap Aluminium Mesh around the CPVC pipes ?

Even going for several turns...

Or, simpler still, wrap the mesh around a set of pipes (because, originally, I was just talking about wrapping each pipe individually).

Like this...


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Scott Davis

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Reply with quote  #13 
Hi Pipscs,

The way the CPVC Ts are constructed, it is tough to get the risers much closer than 2" spacing.  So, if you built two risers assemblies, each with 2" spacing and then stacked them, you would essentially have 1" spacing.  We've done zero testing on this, but my guess is you wouldn't need an other metal at all for additional absorber with that approach.

Again, as always, only side by side testing would tell us for sure how it would compare, but I have no doubt it would work well!

G H, the idea behind the flashing is that it conducts heat that lands between the risers, to them.  A screen would not conduct heat nearly as effectively.


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Garage_Hermit

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Reply with quote  #14 
OK, Scott,
So how about he goes for 1" spacing, wrapped with mesh ?

Some mesh is surely better that all-air ?
Especially with a heavy gage, low-porosity mesh, like I found here...

http://simplysolar.supporttopics.com/post/Black-Screen-Types-6150384?highlight=mesh
http://simplysolar.supporttopics.com/post/Black-Screen-Types-6150384?highlight=mesh" rel="nofollow" target="_blank">
G_H

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Garage_Hermit

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Reply with quote  #15 
Thanks, Scott, I already appreciate what the flashing is for !

However,in an experimental configuration with so little space between risers, and/or offsetting of risers, it is obvious that flashing is starting to become a problem technique, ergo no flashing.

In this case, mesh -- especially a heavy gage, tight-woven mesh -- would certainly be better than air
(because metal is a better conductor than air...).

G_H

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Scott Davis

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Reply with quote  #16 
Hi G H,

Actually, the way I did the flashing on my CPVC collector, simply gluing and not bending at all, it was as easy as falling off a log and the performance speaks for itself.  We are just hypothesizing that with closer riser spacing, you may not need the flashing at all.  At some point that is definitely true, as all the flashing does is transfer the heat that falls between the pipes, to the pipes.  The question is, what spacing achieves that.  Maybe 2", maybe 1.5" or maybe 1"?  We will only be able to find that out with some side by side testing.

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Keith671

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Reply with quote  #17 
I been reading some of the older posts and came across this one on the double layer. I am planning to build an 8x8 with 3" spacing. Would this essentially be the same as building 2 collectors in one? How would you feed a double layer array? Would you just tee the main feed and feed them equal. Same with the return. I like the idea of no aluminum.

Keith R.

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solardan1959

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Reply with quote  #18 
Keith,
   I would love to see the difference between a collector with 3 inch spacing and another same size and spec panel with two layers.  I feel the double layer would greatly outperform the single layer but not double as you suggest for a couple of reasons.  I think the back layer may be slightly more shaded so it would produce slightly less heat.  I also thing the greater amount of flowing water would drop the panel temp slightly so again not double the output.
   Yes tees on both the input and output to split the flow but a valve to adjust flow to each layer would also probably be better so you can balance flow and heat output. I would adjust the flow to ensure both layer were at the same output temp.  Valves are probably not needed but could be an improvement.
The "greatly outperform" statement is a guess on my part with no facts to back it up.
Dan
Scott Davis

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Reply with quote  #19 
Hi Dan,

Additional fluid flow would actually increase output.  Remember, total output is temperature rise X flow rate, so even though the temperature leaving the collector is lower with a higher flow rate, even more heat is returned to the house.

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solardan1959

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Reply with quote  #20 
Hi Scott,
We both said the same thing, I said it would greatly outperform the single layer but probably would not be double as was suggested. (if I did not say it quite that way it, that's what I meant)  I am thinking about doing this with my scrounged glass, I have two 2'X6' pieces and would make one a single layer and the other a double layer. I just need to come up with a couple of storage tanks. or maybe hook them up to a couple of 75' coils of pex to dissipate the heat.
Dan
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