Condensors white or silver?

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On Oct 23, 9:04 am, " snipped-for-privacy@att.bizzzzzzzzzzzz"

If the color of a fridges coils exposed to the sun doesn't matter, then explain how a white roof results in a cooler house than a black roof.
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On Tue, 23 Oct 2012 08:00:39 -0700 (PDT), " snipped-for-privacy@optonline.net"

There are two conversations going on here. I've already said that the sun has a visible component, many times. The reason that the coils in the back of a refrigerator are black is *NOT* because what we see as black is a better radiator.
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On Oct 23, 12:44 pm, " snipped-for-privacy@att.bizzzzzzzzzzzz"

m> wrote:

Then all the experts who agree that home radiators, for example, radiate more heat when painted black instead of white are wrong? Do you agree or disagree that a home radiator painted black will radiate more heat than one painted white? And if you agree, then how can it not be because black is a better radiator?
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On Tue, 23 Oct 2012 10:23:16 -0700 (PDT), " snipped-for-privacy@optonline.net"

Certainly. The performance in the visible range is *no* guarantee of the performance outside the visible range.

Disagree, as stated. It doesn't matter a whit what it's performance is in visible light.

Bad assumption => faulty conclusion, as usual.
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Regardless of the ir absorption qualities, black will probably never be less than white. I see the point. It's easy enough to check which material is going to get hotter in sunlight, I mean radiation.
Greg
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wrote:

Let's try to pin this down a bit. A condenser (or any heat radiator I can think of) is for shedding heat. Heat is shed via IR radiation, conduction, and convection. Conduction and convection don't care about color. Condensors/radiators are normally shaded, so don't absorb solar visible light heat - color won't matter if it's shaded. There's something called emissivity of IR radiation. Depending on what/who you read, emissivity depends on color. Never found a good answer from the internet. But my understanding is that color is inconsequential for common condensors/radiators. It's just bling. Because conduction/convection is doing virtually all the work in moving the heat. So good airflow/fluid flow around the condensor/radiatior is worth a thousand times more consideration than IR emission. The funny part with home radiators is the arguments against using silver or gold paint because of emissivity. Every home radiator I've ever had was painted silver and worked just fine. Maybe it could have been more efficient with a different color. But maybe not. Because conduction is as important as emissivity. It would be expensive to get NASA engineers in to make the measurements. I never bothered with that. NASA has the answers to all this with their space radiators. I've read they use some wildly expensive materials to get best results.
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On Tue, 23 Oct 2012 21:30:42 -0500, Vic Smith

So far, so good. Conducion does care about paint, though. It's an insulator, to some degree or other. ;-)

At least in the first order, yes.

It doesn't depend on color at all. Snow has a very high emissivity, for instance.

Color doesn't. Some materials, of course, have definite colors and that may change emissivity. IIRC, blue anodizing is slightly better than other colors, not because it's blue, rather because of the specific process/chemicals used.

Yes.
Yes.
The paint will reduce conduction (insulation), and therefore convection. Bad idea, except that protecting the surface from corrosion will usually offset the insulation.

Convection and conduction don't work well in space. ;-)
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Again, there are two discussions going on here. First, which will get hotter in sunlight. Black may get hotter because there is significant energy in the visible range (IIRC the peak is in the green/yellow region). There is far more, integrated over the entire EM spectrum, outside the visible range, so black will not necessarily be hotter. Certainly this can be measured with a thermometer (your hand isn't going to do it).
The other issue is whether black makes a better radiator for a 'fridge. This is *not* true because there is no visible light being emitted so it doesn't matter one bit what the color is in the visible range. There just isn't any radiation there. The emissivity at the black-body temperature of the widget matters, not its emissivity in the visible range.
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On Oct 23, 11:01 pm, " snipped-for-privacy@att.bizzzzzzzzzzzz"

The question at hand was obviously not whether the color of a condensor makes a difference for a fridge in general. The question was whether the color of a fridge condensor that is outside, EXPOSED TO SUNLIGHT, makes a difference.
Stormin: "If a refrigerator is used outdoors, in the summer. The condensor on the back, is black tubing. As we know, black absorbs heat from the sun shine, which makes the compressor work harder. "
Now, it seems you agree that white will reflect more of the sunlight. At the same time, white paint and black paint will both allow about the same radiation from the condensor. That means with white you radiate virtually the same amount of heat out, but because it's white, it reflects a lot of heat from the sun that it would absorb if it were black. Ergo, if the condensor was painted white instead of black, it would transfer virtually the same amount of heat via radiation, but it would be heated less by the sun.
And I also totally agree with Vic that the overwhelming heat transfer from the condensor is via convection, not radiation. So, again, which condensor is going to be more efficient? A black one that has to not only get rid of heat from the fridge mainly via convection, but also the additional heat from the sun? Or a white one, that has less heat absorbed from the sun? I vote for white.
Finally, I think the overall effect on efficiency of the fridge from the color of the condensor with sun shining on it is still probably small in the grand scheme of things.
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One vote, white.
To further refine the question. Maybe a white sun shade, about a foot out, would be workable. Plenty of air flow available.
Christopher A. Young Learn more about Jesus www.lds.org .
The question at hand was obviously not whether the color of a condensor makes a difference for a fridge in general. The question was whether the color of a fridge condensor that is outside, EXPOSED TO SUNLIGHT, makes a difference.
Stormin: "If a refrigerator is used outdoors, in the summer. The condensor on the back, is black tubing. As we know, black absorbs heat from the sun shine, which makes the compressor work harder. "
Now, it seems you agree that white will reflect more of the sunlight. At the same time, white paint and black paint will both allow about the same radiation from the condensor. That means with white you radiate virtually the same amount of heat out, but because it's white, it reflects a lot of heat from the sun that it would absorb if it were black. Ergo, if the condensor was painted white instead of black, it would transfer virtually the same amount of heat via radiation, but it would be heated less by the sun.
And I also totally agree with Vic that the overwhelming heat transfer from the condensor is via convection, not radiation. So, again, which condensor is going to be more efficient? A black one that has to not only get rid of heat from the fridge mainly via convection, but also the additional heat from the sun? Or a white one, that has less heat absorbed from the sun? I vote for white.
Finally, I think the overall effect on efficiency of the fridge from the color of the condensor with sun shining on it is still probably small in the grand scheme of things.
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On Wed, 24 Oct 2012 09:27:37 -0400, "Stormin Mormon"

Shade the coils.
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On Wed, 24 Oct 2012 05:51:03 -0700 (PDT), " snipped-for-privacy@optonline.net"

There were two discussions getting mixed together.

That was the original issue, yes, which I answered quite early in the thread (shade it). Like every thread on the Usenet, it went in various directions, including what was the best color for a radiator.

Like always, you put words in people's mouth and then claim victory when they're not correct. Go for it. You will anyway.

I've said that all along. Please do read the thread before making such an ass of yourself.

I'd vote for shading it. Neither black nor white will be satisfactory. Any paint will just add to the problems.

I think you might be wrong. The higher the delta-T the higher the hill the heat has to be pumped.
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On Oct 24, 9:53 am, " snipped-for-privacy@att.bizzzzzzzzzzzz"

Which of course does not answer the direct question. I mean here you are arguing science, so why not give the actual answer to the direct question?
Like every thread on the Usenet, it went in various directions,

I have not put words in anyone's mouth. I just believe I definitively answered the actual question posed by Stormin.

There you go again, getting nasty for no reason. All I said was I agreed with Vic. Apparently you do too, so why the attitude?

And there you go again, as usual, redirecting away from the question if black or white makes a difference.

That's interesting for two reasons. One is that by inference, you apparently agree that for Stormin's stated problem, white versus black does make a difference, though it's small. But as usual, you can't just man up and say so.
And second you obviously have not seen the results of experiments done with central AC units where the compressor/condensor was placed in direct sun versus shade. There was negligible difference in energy used because like the fridge they are highly dependent on the surrounding air temp, not the sunlight falling on the coils.
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On Wed, 24 Oct 2012 09:00:18 -0700 (PDT), " snipped-for-privacy@optonline.net"

Actually, it did.

I did. The binary answers weren't sufficient.

You're a liar but that's nothing new, either.

More lies. ...to be expected.

No, that's the right answer. You're just looking for an excuse to cause trouble. Again.

I said that, dumbass. Good Lord, you're stupid!

Go away, idiot.
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On Oct 24, 1:26 pm, " snipped-for-privacy@att.bizzzzzzzzzzzz"

So typical and sadly to be expected from KRW.
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On Thu, 25 Oct 2012 07:14:49 -0700 (PDT), " snipped-for-privacy@optonline.net"

When you get involved, it can hardly come out differently.
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Yes, and thank you. You are a very kind person.
Someone posted such a study on alt.hvac some years ago. I was amazed to see they reported little difference, if the condensor was in the sun or shade. My intuition is that shade is much better.
Christopher A. Young Learn more about Jesus www.lds.org .
I have not put words in anyone's mouth. I just believe I definitively answered the actual question posed by Stormin.
And second you obviously have not seen the results of experiments done with central AC units where the compressor/condensor was placed in direct sun versus shade. There was negligible difference in energy used because like the fridge they are highly dependent on the surrounding air temp, not the sunlight falling on the coils.
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Exactly. An awning. As easy as a piece of thick cardboard sitting partly on top of the fridge with something to hold it down. Or a tarp. And if painting it did help, which it won't, it would hurt the fridge when you put it back inside.
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If something is black, it will absorbe the most heat, it will also radiate the most heat. It depends on if the air around the object is hotter or colder than the object. As you move to white or silver, this abosrbs and also gives off the least heat.
Being in or out of the sun has nothing to do with this. However if something is in the sun and not shaded from it, the sun will cause black to heat up faster than the silver or white from the rays of the sun.
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On 10/19/2012 7:40 AM, Stormin Mormon wrote:

Condensers and radiators are black for a reason. The darker object emits/loses heat more efficiently. It also absorbs heat better but when the source of heat is gone, heat will be released quicker. In science class, teachers have been demonstrating the effect to students for many years. In your case, I would leave the condenser black and find a way to shade it from direct sunlight with something painted in a light color. ^_^
http://wiki.answers.com/Q/Why_are_car_radiators_painted_black
http://www.bbc.co.uk/schools/gcsebitesize/science/aqa_pre_2011/energy/heatrev2.shtml
https://en.wikipedia.org/wiki/Planck%27s_law_of_black-body_radiation
https://en.wikipedia.org/wiki/Thermal_radiation
There is even special paint for radiators, you don't want too thick a coating.
http://www.eastwood.com/eastwood-radiator-black-paint.html
TDD
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