Google "black body." This is basic physics. It's not a surface area effect.
edit: Here's a table of emissivity for your future reference- http://www.engineeringtoolbox.com/emissivity-coefficients-d_447.html
Sorry but in this case the examples posted above are quite irrelevant.
They refer to FAN cooled heatsinks,
An externally hosted image should be here but it was not working when we last tested it.
with tons of exposed internal surface for better exchange with the air flow, and very poor external surface exposure (which would help radiation).
In this case colour isn´t important, since I guess convection takes away 100X what radiation does.
the thermal engineering is is fairly well understood - and as in most engineering questions - it depends
convective cooling is conduction to the air, less barriers the better, some power law dependency from larger delta T causing more air convective movement
forced air movement with fans usually means thermal conduction of bare metal wins out
for radiation direction of heat transfer and efficiency depend on relative temperature differences, can become larger than convection for >100 C deltas for typical electronic assemblies, but is large power of the delta T and becomes very small for lower delta T
but it can be worthwhile to have better emissivity in low airflow speed natural convection, external heatsinks seeing ~20 C room
as mentioned internal heat from current ripple with ESR should be low in most audio equipment, in fact often the biggest life shortening threat to Al Electrolytics may be from being too close to other heat sources - especially tubes
so you can't make a blanket statement - there are differences depending on internal heat generation, air temperature and flow, flow resistance, relative temperature and solid angle between radiative sources and sinks...
convective cooling is conduction to the air, less barriers the better, some power law dependency from larger delta T causing more air convective movement
forced air movement with fans usually means thermal conduction of bare metal wins out
for radiation direction of heat transfer and efficiency depend on relative temperature differences, can become larger than convection for >100 C deltas for typical electronic assemblies, but is large power of the delta T and becomes very small for lower delta T
but it can be worthwhile to have better emissivity in low airflow speed natural convection, external heatsinks seeing ~20 C room
as mentioned internal heat from current ripple with ESR should be low in most audio equipment, in fact often the biggest life shortening threat to Al Electrolytics may be from being too close to other heat sources - especially tubes
so you can't make a blanket statement - there are differences depending on internal heat generation, air temperature and flow, flow resistance, relative temperature and solid angle between radiative sources and sinks...
I work in pro audio, where the internal cosmetics are not an issue. I am sure in the audiophile area, the internal appearance of an amp is a marketing concern at the very least.
So in my experience, when I open an amp and see caps with the end exposed like that, it is almost always because the heat inside the amp - not necessarily from the cap itself, it is surrounded by heat - has cause the cap wrapper to shrink, thus exposing its own end.
So in my experience, when I open an amp and see caps with the end exposed like that, it is almost always because the heat inside the amp - not necessarily from the cap itself, it is surrounded by heat - has cause the cap wrapper to shrink, thus exposing its own end.
As you live in a democracy you are of course free to believe or disbelieve anything you choose. Your belief does not affect the fact.SonyFan said:
Aluminium is cheap, light in weight, a good heat conductor and easy to machine. The best heatsinks are blackened to aid radiation. Convection does not worry about colour, but may be affected by surface roughness.
Very unlikely, whether the heat source is inside or outside.
I first saw the evidence in a standard school lab experiment when I was about 14. Later I learnt the theory in my physics degree. Note that if there is an external heat source then the black body will get hotter, as it absorbs more.
So the rule is not 'black things are cooler', but 'black things are better coupled to their thermal environment'.
Perhaps just a minor exaggeration, in leiu of a coherent response?SonyFan said:
One man's argument is another man's attempt at teaching basic physics.
To sum up this thread so far:
You think they look nice.
You didn't realise that the change might affect their ripple current rating, because of thermal radiation effects.
I highly doubt this. Capacitors don't get hot as it is. If it does it will be such a small effect it isn't worth discussing here and scaring people off of the idea if they like it. If you have some kind of personal problem message me and we will talk privately like men. That includes my apparent lack of knowledge of physics. If you believe a knowledge of physics is required for removing the shrink wrap on a capacitor or discussing it you are delusional and I would kindly ask that you take that discussion elsewhere. Start your own thread if you want called don't cut your capacitor wrap. Offer up your measurements of temperature differences and ripple performance. I know you won't, because they won't be significant. Next you'll come back and put the burden of proof on me, even though it is your argument. Right? Don't just tell me "facts are facts" because that's not an answer. You have your hypothesis, do your experiment before you come argue your conclusions. Don't tell me you don't need to do the experiment because you know better. Try publishing a conclusion like that.
If you really think the extremely tiny temperature change (that may or may not happen) is really relevant to discussion here you are a troll or suffer a mental disorder. I think you just have a point to make and this isn't the place for it. If you want me to say that you're smarter than me and that you have a superior knowledge on the subject, I will, it is obviously the case. That seems to be what you're angling for if you aren't deranged.
Where do I do this? Read the whole post. I don't deny that it might effect anything, I deny that it is worth discussing for this purpose. If you think it is, you provide the proof, like I said. Your argument, your proof. No proof? Stop posting.
I'm not asking you to do the experiment either, just that you stop acting like you already have.
I would like you back this claim with evidence too. Something you seem shy about. I am not above admitting that I am wrong, I wouldn't be this far if I had never learned anything. If I misspoke stupidly you must understand that my knowledge is limited.
It doesn't change the fact that this mod isn't going to hurt your capacitors or cause any significant change in performance. For the purpose of this thread, that is what is important. This doesn't mean I am denying it will change performance at all. Smudging the can up with your hand probably would under the right conditions. I am denying the significance of this effect in this application specifically.
This discussion of thermal considerations is all very interesting, but what I don't get is why anybody would want to cut slices of plastic off in the first place. Don't get me wrong - I've got nothing against audiophools playing with razor blades, I'm just wondering what the motivation is.
Purely cosmetic. There is nothing to be gained but looks, I just like the big shiny top exposed. This was done purposefully on some new production caps back in time and still is today by Elna on certain models. As discussed it may in fact be detrimental. I don't think it's detrimental enough to stop me from doing it. My cut caps are cool to the touch under load just like covered ones.
I just got off Skype with a good friend who is self-employed as a robotics engineer and PCB designer. I asked about the cut shrink wrap and he told me that he believes this is done for "pick and place" and similar assembly machines. It provides a more uniform top, and he says a lot of parts are made now with considerations like this for automated assembly. He also laughed when I asked about black heat sinks and said of course they are better. I have learned something.
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