How well do different metals (specifically copper and aluminium) conduct heat to air?

[Commander Kinsey]

How well do different metals (specifically copper and aluminium) conduct heat to air?

[SH]

Theres these wonderful inventions called:

Bing DuckDuckGo Google

So if you search for "copper thermal properties"

and search for "Aluminium thermal properties"

You should also search "thermal emissivity"

[Brian Gaff]

The amplifier I am listening to at this time has a heat pipe of copper on its output devices, ending in an aluminium heat sink outside of the area where it might heat the pcb. I am certainly not sure how heat pipes actually work, but they do, you can tell by just touching the heat sink. Is it that old fluid evaporation again? Brian

[Max Demian]

Painted black -> very well Painted white -> not so well

That's radiation, mainly. Conduction is better, depending on whether there's space for convection or there's forced convection (with a fan, say).

I don't think the type of metal [1] makes any difference, and all metals conduct heat well.

[1] Not if you an astronomer. Astronomers call all elements that aren't hydrogen or helium "metals".

[Paul]

A heat pipe (with a couple drops of working fluid inside), transmits more heat than the equivalent diameter *solid copper* pipe. By a significant ratio.

And the manufacture of heatpipes has improved to the point, you don't have to worry nearly as much about leakage. Computer coolers use multiple pipes, so if the fluid disappeared from one pipe, the other pipes are still there. A pipe does not have to be at atmospheric pressure either. It could be 2 ATM or

0.5 ATM.

There was one report, of a cooler where the pipes obviously had not been filled, and the cooler would not "make the fins hot" meaning all pipes failed. A dry heatpipe conducts almost no heat at all, as it's a "long path" of significant thermal resistance.

And thermal resistance, is why making the fins on a cooler longer, has diminishing effect. A 40mmx40mm Al chip cooler which is three inches tall, is not significantly better than one where the fins are one inch tall. The long/thin fin is not able to transport heat out to the end of the fin. And this is why heatpipes exist, to solve the transport problem, and put the heat in the right place to get the benefit from the fins.

If the entire heatpipe is too hot, the transport no longer works. The heatpipe behavior is not exactly a linear function under all circumstances. CPU heatsinks, have a proposed max power they are rated for, where the end of the heatpipe still condenses fluid and the flux transport is working. You cannot pump 1kW of energy into a heatpipe cooler, if it is rated at 180W, because it then behaves as a rather shabby "thin" ally cooler. And does almost no cooling at all.

Pure Al | Al with copper slug | Increasing Solid copper or copper with nickel plate | goodness Copper baseplate, copper heatpipes, Al fins V

In the previous table, moving air through the fins, helps. Up to the asymptotic limit of around 800 LFPM. We had a piece of equipment once, where the air movement was 800 LFPM (and you needed to wear ear protection), so, um, don't do that :-)

Paul

[Paul]

Yes, the metal type makes a difference.

Paul

[Fredxx]

Being pedantic, conduction to air is seen as convection. The surface area, ie roughness is perhaps the best indicator and not colour.

When it comes to radiation, the colour perceived by our eyes is not a good indicator at the wavelength of interest at which radiation of a room temperature object.

Again surface texture is key. A heavily anodised aluminium surface is actually a good emitter, a polished one would be reflective.

Well, it's the surface temperature that matters rather than the metal.

What do they call metallic hydrogen below the surface of Jupiter?

[invalid unparseable]

I read: "A good conductor of heat will have low specific heat capacity." So, copper is better.

[Smolley]

Silver is better.

[Michael Chare]

The idea of a CPU cooler that uses a heat pipe is quite interesting. I wonder if a heat pipe cooler would be better at cooling my PC without running the fan than the cooler I bought some years ago.

[Andrew]

My HP AIO PC has what looks like a copper heatpipe transferring the CPU heat to an aluminium finned arrangement surrounding the fan.

[Andrew]

And painted matt black even better

[Ian Jackson]

Doesn't the paint create an (albeit thin) layer of low thermal conductivity, which tends to 'keep the heat in'?

[Ian Jackson]

But won't this depend on its thickness?

[Fredxx]

And it's properties in the long wave band, a long way from what your eyes see? It is credible to have a visibly white surface with a far higher emissivity than a black surface.

I have no idea why so many think a black painted surface is going to be better than a white surface.

[Ed Pawlowski]

Copper absorbs better, aluminum dissipates it faster. Few a few pennies more, gold wold be even batter.

[Paul]

Zalman made a computer case, with extensive used of heat pipes. The chassis walls of the PC, provided convection cooling. Good for a PC of less than 400W power consumption or so.

The power supply for that, had no fan in it. But a practical PC builder, would still fit a fan and move some quantity of air through the case, just to prevent hot spots and premature failures. If you were a practical builder, you would likely use an IR camera to ascertain whether your "kit" was suited to such poor cooling.

Some modern CPUs and motherboards, the consumption is low enough, you could indeed use a TNN500AF without any fan whatsoever. But if you were building a computer with 64 cores and an expensive vid card, that box can't cool it via external convection alone.

The box was prohibitively expensive, but some recording studios apparently set up some PCs that way. Convection cooled.

Paul

[Reentrant]

Comprehensive table here:

[micky]

Good question.

Why do so many people, even in hot, warm, and temperate climates, buy black cars? In the summer they are intolerable hot when entered and, even if one has AC, for several minutes afterwards. (They are also harder to see and more likely to be hit.)

Why do people with convertibles buy cars with black seats? My first two came with black seats and trying to sit down on one wearing short pants is murder**. Since then, I've bought nothing but tan seats, or white.

But one can tell from what is for sale that many other still buy cars with black seats and black roofs.

**I learned to hold my body a few inches over the seat for a couple minutes while the black seat radiated its heat without being provided any more, and that cooled it enough to sit down.

[Cindy Hamilton]

Because they look so badass.

Cloth, leather, or vinyl?