Noctua Introduces Chromax.black CPU Coolers

[EarthDog]

Right.. but we aren't in a vacuum.

Conduction doesn't need air... it moves through, in this case, a metal heatsink.

The heat absorbed by the heatsink via conduction has to go somewhere and that process has a name. It isn't radiating off the heatsink (Stefan-Boltzman law?)?

http://physics.bu.edu/~duffy/py105/Heattransfer.html

Everything around us takes in energy from radiation, and gives it off in the form of radiation. When everything is at the same temperature, the amount of energy received is equal to the amount given off. Because there is no net change in energy, no temperature changes occur. When things are at different temperatures, however, the hotter objects give off more energy in the form of radiation than they take in; the reverse is true for the colder objects.

Sorry, this clearly isn't my forte... lol.

 

[Zerileous]

I think mackerel is saying the heat gets into the air via conduction, hence why we keep forcing molecules of air to smack into the surface of the HSF (or rad for that matter). Of course I haven't finished my coffee yet so I may have completely missed the point .

 

[EarthDog]

Right. And there are properties for how fast that enerygy can be absorbed and dissipated.

I think what may be throwing me off is this (definition of conduction): When heat is transferred via conduction, the substance itself does not flow; rather, heat is transferred internally, by vibrations of atoms and molecules.

The air molecules from fans are there to raise the temperature difference and removal of heat from the object. It may be conduction.... I don't know...air is an insulator...

https://physics.stackexchange.com/q...onditions-for-heat-transfer-from-metal-to-air

The other heat flows will be caused by convection between the box and the air, and radiation.

They are calling it convection from source to air....


Absorption of heat and radiation of heat are different properties, right?

 

[Zerileous]

Yeah convection is the word there https://keydifferences.com/difference-between-conduction-convection-and-radiation.html

I don't think radiation is going to play a significant role regardless. Even in "passive" heatsinks, I'm assuming that airflow from case fans contributes to convection which is the primary method of removing the heat.

 

[EarthDog]

Right... I knew it wasn't conduction, but didn't know which it was.

 

[mackerel]

Let us imagine a simplified case where there is no fan. Heat will conduct from the heatsink to air. And there it will stay. By blowing that air through, we get cooler air in, and more heat transfer as it is related to the temperature difference. It doesn't have to be the same material. The only requirement for conduction is for matter to be in physical contact.

If you consider air to be a conductor or insulator is kinda relative. It isn't a great conductor so an air gap can be effective as an insulator. But that isn't to say it doesn't hold heat at all.

Convection I don't think is really applicable in this case, at least not where fans are in use. Convection in a fluid is when the fluid near the heat source gets warmer, and makes it less dense. It will tend to flow upwards, and be replaced by cooler, denser fluid. This can turn into get a flow pattern. There are some passive cooled cases which rely on this. I think one of the old Mac bins used it also. No moving parts (other than the air). If you're pushing air with a fan, I don't think you can call it convection.

 

[EarthDog]

What about the links and passages I quoted?

Specifically this: heat is transferred internally, by vibrations of atoms and molecules.

Doesnt the heat off the heatsink rise and mix with the cooler air and is convection?

 

[Zerileous]

This conversation makes me feel like I need to go re-take high school physics

If convection is not applicable when fans are in use, are convection ovens a misnomer? https://www.thekitchn.com/whats-a-c...e-it-appliance-guides-from-the-kitchen-216549

 

[EarthDog]

Same... I know I am missing something here. I think we all are, honestly.

I do know that absorption and dissipation of heat are two different properties of a material (think aluminum foil covering food in your oven... its hot when it is touching something, but then cools incredibly quickly). I just don't know what that process is called with the heat moving into the air.

I know by simply feeling it there is convection and radiation on a heatsink, right???? Let's say you run a heatsink and fan and it gets saturated. You turn it off and you can feel the heat coming off of the heatsink. Is the heatsink radiating the heat off of it? Convecting? I don't know. I don't feel conduction is it though because the definition specifically mentions internal movements of molecules. There are also equations for convection and air coefficients too... so convection isn't only in a liquid.

 

[mackerel]

I think we're over-complicating things now... conduction, physical heat transfer through contact. That includes metal to air. Once the air gets warmer, convection may happen.

I've not heard of a convection oven before. We call them fan assisted ovens here. Convection is the physics process. A fan would have a similar effect of moving the fluid around. Convection applies to fluids, could be liquid or gas.

A hot heatsink without a fan on it, at a distance you will be feeling a combination of radiated heat and convection. I don't know in what combination. If you feel from the side, that'll be radiated heat only. Above it, could be convection too. If you touch the heatsink, then you get conduction.

I'm not gonna get into saturation given the way things are going here...

 

[EarthDog]

Can you address the difference between your definition of conduction and what I've linked a couple of times?

heat is transferred internally, by vibrations of atoms and molecules.

No definition (ive seen so far) of conduction infers or alludes to transferring outside of the material...


EDIT: looks like it is all of the above...

Heat is a form of energy that manifests itself in the motion of molecules and atoms, as well as subatomic particles. Heat energy can be transferred by conduction, convection, or radiation.

I think I get it........... or will say I do so we don't keep going in circles, lol.

 

[mackerel]

It looks like we're digging into a level beyond my understanding and ability to communicate. There's a certain language that seems to be used that doesn't necessarily translate into a layman reading.

https://en.wikipedia.org/wiki/Thermal_conduction

Say you have a homogeneous solid. That fits into the description of conduction right? What if it were less uniform but still a solid? Same happens, but maybe at different rates through the various parts. In the more generalised case, anything in physical contact with anything else can conduct heat to it. You still get movement of atoms, molecules, electrons, whatever. If they meet, they can transfer heat.

 

[EarthDog]

But it specifcally says INTERNALLY.... lol.

From your link...

In conduction, the heat flow is within and through the body itself. In contrast, in heat transfer by thermal radiation, the transfer is often between bodies, which may be separated spatially. Also possible is transfer of heat by a combination of conduction and thermal radiation. In convection, internal energy is carried between bodies by a moving material carrier. In solids, conduction is mediated by the combination of vibrations and collisions of molecules, of propagation and collisions of phonons, and of diffusion and collisions of free electrons. In gases and liquids, conduction is due to the collisions and diffusion of molecules during their random motion. Photons in this context do not collide with one another, and so heat transport by electromagnetic radiation is conceptually distinct from heat conduction by microscopic diffusion and collisions of material particles and phonons. But the distinction is often not easily observed, unless the material is semi-transparent.

In the engineering sciences, heat transfer includes the processes of thermal radiation, convection, and sometimes mass transfer. Usually, more than one of these processes occurs in a given situation. The conventional symbol for thermal conductivity is k.

Anyway, I digress.

 

[trents]

Normally, this would be true, which is why Noctua took so long researching this. Their CEO addressed this specific point in their press release.

Can you link this?

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Conduction is how it moves heat through itself, radiation is how it gets rid of that heat, no? I'd think most any paint would act as some some sort of insulator unless the paint itself had some added properties to move that heat energy?

This makes sense to me. There is a difference between something being black and being painted black it would seem to me when it comes to heat absorption and dissipation.

 

[Woomack]

Noctua coolers arrived but I had only time to test one of them. U12S chromax performs about the same as U12A +/-1°C using Ryzen 3900X CPU. The U12S comes with one fan but after adding 2nd one, temps are not much better - about 2°C lower temps with 2 fans. Pretty much the same difference as with the D9L and 1 or 2 fans.

 

[trents]

The black is cosmetic like LEDs on RAM and motherboards.

 

[freeagent]

Supposedly it marks up pretty easily too, so be gentle.

 

[Woomack]

The black is cosmetic like LEDs on RAM and motherboards.

The U12A is slightly thicker and has 1 heatpipe more than the U12S so at least on the 3900X I was expecting a bit more than +/- 1°C.

Supposedly it marks up pretty easily too, so be gentle.

Actually, I already scratched it a bit with a screwdriver (not on purpose) and it made only a thin line that wasn't going through the paint. I guess no one would notice that at first sight and would have to take a closer look to actually see it. Also, fingerprints are not visible on this paint. Even on the "standard" version, it was visible and no one is installing coolers wearing gloves

 

[trents]

"The U12A is slightly thicker and has 1 heatpipe more than the U12S so at least on the 3900X I was expecting a bit more than +/- 1°C."

Probably to compensate for the insulating effect of the paint.

 

[Woomack]

Another way actually, thinner but black version of the cooler which supposes to be worse is the U12S, and it performs almost as good as the thicker, U12A cooler. Also, U12S has "focussed flow" fans in more standard design while U12A has Sterrox fans which suppose to deliver higher performance but have no "focused flow" design.
I don't think that black paint on this cooler really matters in thermal performance or the difference is really low. For me, the performance of the U12S/black is higher than expected but maybe it's because I was testing them on AMD where is a low difference between 6,8 and 12 cores.

U12A is this https://noctua.at/en/products/cpu-cooler-retail/nh-u12a
U12S chromax.black is this https://noctua.at/en/products/cpu-cooler-retail/nh-u12s-chromax-black