The JAD V2 Kit Showcase - 1x18650 Heavy-Duty C6

[Wolfman29]

One complaint: Al does not dissipate heat more quickly than Cu. That's a common misconception. A solid copper heatsink is always better than a solid Al heatsink.

 

[Seoul_lasers]

One complaint: Al does not dissipate heat more quickly than Cu. That's a common misconception. A solid copper heatsink is always better than a solid Al heatsink.

Totally, agree!!!!!!

After playing with a number of copper sinks and Ryan's Copper laser, Copper is fantastically more efficient than Aluminum at conducting heat. Copper, Silver would be even more conductive, abiet much more expensive!

Aluminum is used simply because it is cheap and light weight. Copper is heavy and quite a bit more $$.

It's simple science really, Aluminum = 250 W/m.K vs Copper = 401 W/m.K
W/m.K = Watts per meter Kelvin. The only material better than Copper is Silver at 429 W/m.K, Gold actually isn't that great with heat coming in at just 310W/m.K

 

[Wolfman29]

Yup. That's the only reason why!

And that's the same reason I want a solid silver laser >

 

[RyanElectro]

Actually, I beg to differ. No doubt that copper does conducts heat better as well as absorb more heat. But Aluminum definitely dissipates heat faster. I can actually feel it in my hands, aluminum builds cooling down faster than copper.

I made this conclusion with a few others after reading and posting on rhd's "copper, copper, copper well maybe not" thread. IIRC, I think there was a statistic and various comments somewhere in that thread that pointed out aluminum dissipates heat faster than copper.

I'm almost certain of this, that's why CPU heatsinks, GFX cards heatsinks, no matter how expensive the card, all have copper as direct contact to the heatsource, but aluminum fins to dissipate heat, not copper fins. I don't think it's simply a cost issue either.

It's simple science really, Aluminum = 250 W/m.K vs Copper = 401 W/m.K
W/m.K = Watts per meter Kelvin. The only material better than Copper is Silver at 429 W/m.K, Gold actually isn't that great with heat coming in at just 310W/m.K

You're talking about heat conductivity, which I've always agreed on as well. But speed of dissipation is quite different. Copper absorbs more heat and absorbs it fast, but it also holds on to heat longer, making it an excellent transferrer of heat (ie. explains the widespread use of copper heat pipes in heatsink designs), but not a dissipater of heat (where aluminum fares better).

Just my theory & experience with both materials... I would go looking for that statistic but I'm real tired right now just came home from a tennis match. You guys can try looking for it if you want

Btw that solid silver laser is a must do. I say it should have some holy/christian design cues like a cross haha. It's like a silver sword or silver bullet but instead a laser. +10 damage against undead haha, great for zombie apocalypses.

 

[Wolfman29]

This is why you're viewed as arrogant. I know what I am talking about here. I do physics.

You feel aluminum cool down faster because it has a smaller heat capacity. That means that, for a joule of energy lost in heat, it will drop in temperature more than copper will. That does not mean it will "dissipate heat" faster. Copper has a higher thermal conductivity, meaning its interface with air is better "thermal contact" than aluminum's. The only reason it seems it takes a while for copper to cool down is because it has such a huge specific heat as well - it takes a long time to drop in temperature, it degree for degree, it releases significantly more energy than aluminum.

 

[RyanElectro]

This is why you're viewed as arrogant. I know what I am talking about here. I do physics.

You feel aluminum cool down faster because it has a smaller heat capacity. That means that, for a joule of energy lost in heat, it will drop in temperature more than copper will. That does not mean it will "dissipate heat" faster. Copper has a higher thermal conductivity, meaning its interface with air is better "thermal contact" than aluminum's. The only reason it seems it takes a while for copper to cool down is because it has such a huge specific heat as well - it takes a long time to drop in temperature, it degree for degree, it releases significantly more energy than aluminum.

Gee, I even tried my best to edit the post like crazy to ensure I don't sound "arrogant".

Strangely, it is also your post that sounds arrogant to me, as if you're saying you're smarter than me when you say, "I know what I am talking about here. I do physics." Like I'm some idiot who knows nothing.

I do think I'm right, but it seems that I am not able to affirm my point without sounding "arrogant". Please realize just because I think I'm right doesn't mean I'm arrogant, it would be arrogant if I thought I was right because I think I am smarter than you. But no, it would be stupid to think that. I thought I was right based on my experiences, as well as from a collective discussion in rhd's "copper, copper, copper" thread.

Though your last explanation does point at a source of my theory: aluminum having lower heat capacity, therefore dissipates heat faster. However, I doubt this point: "Copper has a higher thermal conductivity, meaning its interface with air is better "thermal contact" than aluminum's." I think it's a stretch to say because a material has higher thermal conductivity, that it has a better "thermal contact" with air. Air acts very differently to metal, and is a horrible conductor of heat, will there even be much of a difference vs. aluminum?

The biggest thing, is that I physically feel aluminum cooling at a faster rate than copper. And you have explained that phenomenon well. However, only way to truly figure this out is via practical experiment. I cannot merely buy that "you do physics" and therefore assume everything you say must be true. On the contrary, I do view most of your points as valid plausible explanations.

I mean not to offend, really, and I rather not keep saying this. This is the just way I type/speak, I am really trying to sound "more non-arrogant" but this is me trying as hard as hell man I'd like to say "get used to it" but again I don't wanna sound arrogant. Don't get the idea that I only want to be right. I have no problems being wrong, I am here for science and truth too. I just want to make sure when I do edit my knowledge bank, it is edited correctly. Also it's worth to note I am a natural skeptic

Thanks the explanation though, interesting read.

 

[Wolfman29]

Apologies - it just bugs me when people accept common misconceptions as true. But air, much like all materials (metals included) have thermal conductivity.

And the only reason aluminum SEEMS to cool faster is because really, it stores less energy. Yet, copper gets rid of energy faster overall than aluminum.

I'd have to check back again, but I am pretty sure the rate of heat transfer is proportional to the product of the two heat conductivitys.

 

[RyanElectro]

Apologies - it just bugs me when people accept common misconceptions as true. But air, much like all materials (metals included) have thermal conductivity.

And the only reason aluminum SEEMS to cool faster is because really, it stores less energy. Yet, copper gets rid of energy faster overall than aluminum.

I'd have to check back again, but I am pretty sure the rate of heat transfer is proportional to the product of the two heat conductivitys.

It's all good man, I understand pet peeves, I've got quite a few myself

But I do think that's really good explanation to the phenomenon of Al cooling faster, and I'll actually be surprised if you're wrong about that. I'm starting to lean on your theory but only thing stopping me is that I really don't think, because of copper's higher thermal conductivity, that it will make much of a substantial difference in dissipation to air, because air is horrible at conducting heat. In essence, is thermal conductivity linearly related to speed of dissipation to air?

I will try to find some physics majors or profs and get a second opinion, though I know very few people in this field (glad you're in it).

But I'm definitely interested to know the scientific truth now. Thanks for your input

 

[Wolfman29]

Well, all other things considered, why would aluminum dissipate heat faster than copper? What other physical property besides thermal conductivity and specific heat relates to the thermal transfer to any other media?

None.

Specific heat tells how much energy it can store per degree. This does not relate to how much energy it can dissipate, only how "cool" it gets per unit of dissipated energy. The only other property is the thermal conductivity. That solely governs thermal dissipation.

 

[RyanElectro]

Well, all other things considered, why would aluminum dissipate heat faster than copper? What other physical property besides thermal conductivity and specific heat relates to the thermal transfer to any other media?

None.

Specific heat tells how much energy it can store per degree. This does not relate to how much energy it can dissipate, only how "cool" it gets per unit of dissipated energy. The only other property is the thermal conductivity. That solely governs thermal dissipation.

Hmm, interesting, I was trying to think of that as well. I can't really think in equations as I'm not a physics major. But I can think in theory. Perhaps being much less dense, there is a lot more space between particles, therefore the particles "have more surrounding air" to cool down them. Less material + more air, in the same amount of space = faster dissipation.

What do you think?

 

[Wolfman29]

Nuuuu. There is no air in aluminum. Actually, being less dense, there would be less aluminum atoms to contact the air than copper =p

 

[foulmist]

Hmm I found this on another forum which may clear things up a bit:
EDIT: what I understood is: in working (steady state) copper IS BETTER! When in off state ALUMINUM will TRANSFER the heat into the AIR faster and will cool faster (but only when the device is OFF [the heat source is gone]) Correct?

False Perception: Since aluminum stores less energy per volume, it must be more efficient at getting rid of heat.

Truth: During steady-state operation, there is no net energy storage in the heat sink or fins/pins; hence, specific heat plays no part in steady-state performance.

Fact 2: Aluminum has lower density than Copper. Volume for volume, aluminum is much lighter than copper.

False Perception: Weight acts as a “sink” for heat. Since copper is more dense, it absorbs heat well from the die. Since aluminum is light, it gets rid of heat more effectively than copper.

Truth: Density has no direct relationship with steady-state heat transfer.

Fact 3: A small volume of aluminum will cool more quickly than an equal volume of copper once the heat source is gone. This is due to the same reason as fact #1, namely there is less energy stored per unit volume is aluminum than copper. This is, however, a transient condition. Heat transfer from a computer is a steady-state condition where the temperature of the heat sink remains relatively constant. The specific heat of a material partially determines how a material responds to transient conditions but has no effect at all on steady-state operation.

False Perception: Since aluminum cools more quickly once a heat source is removed, it must be more efficient at convection.

Truth: The heat source driving energy into the heat sink remains in effect until you turn off your computer. If you have aluminum pins or fins, congratulations, they will cool off more quickly than copper ones after you shutdown your PC.

The only properties belonging to the solid that affect convection are geometry and surface temperature. The fluid stream has no knowledge of what lies beneath the surface of the material. If an aluminum and copper item have the same precise geometry including microscopic surface details and they have the same temperature then they will have precisely the same convection.

If you are still unconvinced, consider this little thought exercise. Imagine a magic heat sink pin. This magic pin has an adjustable conduction coefficient that allows you to dial the conduction coefficient between a range of zero and infinity. Heat enters the magic pin through its connection to the heat sink. Heat leaves the magic pin through air convection.

When the pin’s conduction coefficient is very near zero, heat has a tough time transferring down the length of the pin. The end near the heat sink gets very hot, while the opposite end remains cool. Convection can only occur with a temperature differential, thus only occurs near the hot end. Most of the pin does no useful work.

When the pin’s conduction coefficient is near infinity, there is little resistance to conduction. The pin will attain a nearly uniform temperature over its entire length and convection will occur over its entire length.

Now let us go back to the aluminum versus copper debate. Copper’s higher conductivity means is that a thinner copper fin can transmit as much heat as a thicker aluminum fin. However, on a weight-basis, aluminum can conduct more heat than copper. If weight was no object, copper holds the edge. When weight is a limitation, aluminum has the advantage. Conductivity multiplied by density is a "weighted" measure of a material’s conduction efficiency. It is this "weighted" efficiency that leads to the use of aluminum in the fins/pins of many heat sinks. It is certainly not because "aluminum gets rid of heat better than copper".

 

[RyanElectro]

Nuuuu. There is no air in aluminum. Actually, being less dense, there would be less aluminum atoms to contact the air than copper =p

haha >.< noo I mean air at a molecular level.

Wouldn't you say a hot, solid metal box suspended in air inside a large room would cool down faster than two hot, solid metal boxes at the same temperature inside the same room. At the particle-level, that's like comparing a less dense material to a denser material. The less dense material has less particles in the same space, when both materials are heated to the same temperature, the less dense material should drop in temperature faster than the denser material.

I think it does... doens't it?

EDIT:
Haha, I was typing my post when foulmist's posted:

False Perception: Weight acts as a “sink” for heat. Since copper is more dense, it absorbs heat well from the die. Since aluminum is light, it gets rid of heat more effectively than copper.

Truth: Density has no direct relationship with steady-state heat transfer.

&

A small volume of aluminum will cool more quickly than an equal volume of copper once the heat source is gone.

Seems like my theory is wrong. But my conclusion is correct? This is very interesting. So it realy is a false perception, but for other reasons, aluminum still "dissipates" faster when the heat source is removed. It is accurate to my experience, where I test the cooling rate after heat source is removed being faster for Al than Cu

Copper’s higher conductivity means is that a thinner copper fin can transmit as much heat as a thicker aluminum fin. However, on a weight-basis, aluminum can conduct more heat than copper. If weight was no object, copper holds the edge. When weight is a limitation, aluminum has the advantage. Conductivity multiplied by density is a "weighted" measure of a material’s conduction efficiency. It is this "weighted" efficiency that leads to the use of aluminum in the fins/pins of many heat sinks. It is certainly not because "aluminum gets rid of heat better than copper.

Very.. freaking.. interesting.

Thanks foulmist, that's a really good informative post. Is it a trusted source though?

 

[Wolfman29]

Foulmist - the source is right, your conclusion is wrong.

While yes, it does cool faster when the heat source is removed, that does not mean that it dissipates energy faster. Because aluminum stores less energy per unit temperature, even if it dissipates less energy per second, it will still drop in temperature more - much more, leading to this misconception.

Ryan: your example would work if the heat capacity of our environment were not near infinite. As it is, heatsinks can dissipate thousands of watts into the air, and, due to the convection, they can continue to dissipate that much without drastically increasing the average temperature of the air.

Like I said, aluminum will not dissipate faster. It will simply cool off faster. Energy is not equal to temperature, rather, it is simply proportional, related by the specific heat. Because aluminum's specific heat is smaller, it will cool off more, but lose less energy, per unit time.

Imagine a copper and aluminum chunk, each heatsinking a 10W source of heat with the same geometry.

For the sake of the example, I won't use real values.

The copper will heat up, for example, 2 degrees in the course of 5 seconds of the source being active. The aluminum, on the other hand, may heat up 4 degrees in the course of 5 seconds of the source being active. This is because aluminum has less specific heat capacity.

Then, the source is turned off.

Now, even though copper can lose that 50J of energy faster than aluminum can, the aluminum may drop to 1 degree at the same time copper can drop to 0 degrees above ambient. Therefore, aluminum has dropped 3 degrees in the time it takes copper to drop 2 degrees. So, it seems that aluminum has cooled off faster, when in reality, it hasn't - it merely needs to lose less energy per unit degree in order to cool off.

 

[foulmist]

ok after reading all of this I think I will never understand how it works so I will just not look into it that much. lol stupid me It's all messed up in my head :crazy:

 

[RyanElectro]

I understand what Wolf is saying, I like his explanations a lot especially with the Al and Cu chunk bit. As far as logic is concerned, he makes perfect sense. "Energy is not equal to temperature" - it's nature's way of tricking our perceptions, is why I felt Al cooling faster.

Though, if Al "merely needs to lose less energy per unit degree in order to cool off", then couldn't it be said it's "more efficient at losing heat"?

I understand energy absorbed doesn't translate to equal temperature increases in both materials, but let's just consider temperature by itself, since that's all we care regarding duty cycles and use. If both materials were heated to 80C, then the heat source turned off... the Al material will reach ambient temperature faster than copper right? But the copper will take longer to reach that 80C in the first place? Am I somewhere in the ball park with this? lol