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Author Topic: Thermal absorber question  (Read 4638 times)

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madlabs

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Thermal absorber question
« on: July 10, 2013, 12:27:52 PM »
Hi All,

So I'm putting the pieces together for a solar heat collector for a food dehydrator. Very simple design.


----------------- glazing

----------------- Aluminum siding, painted black

========== 1" foam insulation with reflective side up.

The question is: Does it matter if I paint the back of the aluminum black? Very little light, if any, will get down there.

Jonathan
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SteveCH

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Re: Thermal absorber question
« Reply #1 on: July 10, 2013, 02:41:39 PM »
If I'm picturing this accurately, there is no reason to paint the back side of the aluminum.
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Larsmartinxt

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Re: Thermal absorber question
« Reply #2 on: July 10, 2013, 04:02:20 PM »
Quote from: SteveCH on July 10, 2013, 02:41:39 PM
If I'm picturing this accurately, there is no reason to paint the back side of the aluminum.
Why not?
I would paint the entire inside of that box black to absorb as much heat as possible
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madlabs

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Re: Thermal absorber question
« Reply #3 on: July 10, 2013, 08:45:02 PM »
Why not would be that I would have to buy another can of paint! :-0

And I'd like to know if it matters. As I said, there will be essentially no light down there. But does the reflective foil on the insulation reflect radiant heat?

Jonathan
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Bruce S

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Re: Thermal absorber question
« Reply #4 on: July 11, 2013, 09:28:31 AM »
Mad;
I would say it doesn't matter.

Here's a pic of our solar dryer inside. I thought about painting the inside, but after covering it and watching the inside temps hit 107F I'm inclined not to add anything. This also helps during our semi-annual clean ups.
Bruce S
PS>> I left it large so you can see the details. IF way too large let me know and I'll replace with smaller version.
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madlabs

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Re: Thermal absorber question
« Reply #5 on: July 11, 2013, 10:35:45 AM »
Turns out it does matter in the collector. Painting the back of the aluminum absorber is the way to go. In fact, I'm a little embarassed that I asked.

Bruce, nice rack! ;-) So the sides are metal too? More pics please! But maybe post 'em in the dehydrator thread so folks can find 'em?

Thanks!

Jonathan

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Bruce S

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Re: Thermal absorber question
« Reply #6 on: July 11, 2013, 02:22:23 PM »
Just a quick post to say yes, it's all metal.
I'll post other pics, not so large in view size over in the other thread.
Cheers
Bruce S
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Mary B

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Re: Thermal absorber question
« Reply #7 on: July 11, 2013, 02:39:03 PM »
Sheet pan rack, your local  restaurant supply will have new ones plus auctions  of closed down  restaurants will often have them show up.
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Bruce S

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Re: Thermal absorber question
« Reply #8 on: July 11, 2013, 02:54:04 PM »
OR on Craigslist :). That's where my wife found the one we used. It's double sided.
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