A little lesson on heatsinks

[EpicHam]

If your concern is runtime, there are other methods that will net an infinite increase in runtime.

Since I know how much you hate analogies, I'll add one. If you want to get better distance on a tank of gas, you could get a bigger gas tank... or you could get a more efficient car.



People often quote these numbers. But they are a bit misleading.

Take a length of wire, for example. Is 1mΩ/m better than 2mΩ/m? Yes, but only by a small amount. Both will work very well as a conductor. Take the reciprocal, however, and you have CONDUCTIVITY: 1000S/m and 500S/m respectively. Surely 1000 is WAY better than 500, right?

look at my earlier maths on the page 1 comment , I've shown that for the same heat sink design (volume fixed , material variable case)
Copper heat sink holds more joules of heat than aluminium.

No , aluminium is not strong. It has a crap young's modulus and modulus of elasticity when you take into account that lasers tend to roll off tables.
Things DO tend to become more stable <----- Nerd joke




Are you sure your university cert isn't something written on a tissue paper? Cos I'm a bit skeptical


The question of whether you should choose a copper or an aluminum heatsink has never been a question of which one has a better performance , its always about the WALLET.
For 2 reason.
1: Higher Thermal Conductivity
2: Higher heat retention per m3 of copper

Facts:

Thermal Conductivity:
Copper: 401 W/(m.K)
Aluminium's : 205 W/(m.K)

Specific Heat Capacity:
Copper's specific capacity ( 0.3850J/g oC) is lower than aluminum by a factor of 3,
Aluminium 's higher specific capacity (0.902J/g oC) makes it "better" at "sinking heat" from the surface but that can't be farther from the truth

Density
Copper : 8940 (kg/m3)
Aluminium : 2712 (kg/m3)




Case Study :

To put things into perspective .

Assuming a given heatsink is the same in design and only differ in material .

Our hypothetical heatsink (can't be arsed to bring out my casio) of has a volume of 1m3 :beer:

Joules needed to increased the heatsink temperature by 1C
Copper : 8940000 x 0.385 = 3441.900kJ
Aluminium :2712000 x 0.902 = 2446.224 kJ


In conclusion.

Better Volumetric heat sinking : COPPER! WINS!
Heat transmissivity : COPPER WINS!

And we aren't even taking into the equilibrium condition where aluminum will just end up trapping heat within the diode




Umm...

I don't think diode lasers face such a problem .
Since the diode will pop first ......


PS: It has been almost 2 semesters since my Thermomechanics course . So if I got anything wrong , please DO point it out. And if you feel like up to it . Do the maths for me





EDIT: Am i being trolled???? Cos I think I am :undecided:

 

[TheDukeAnumber1]

Since I know how much you hate analogies, I'll add one. If you want to get better distance on a tank of gas, you could get a bigger gas tank... or you could get a more efficient car.

Guahhhh he knows my weakness... :scowl:

jk...

 

[Cyparagon]

Copper heat sink holds more joules of heat than aluminium.

And a 15 gallon tank holds more fuel than a 10 gallon tank. It does NOT make the car better.
You forgot to read the first part of my post entirely. That only serves to increase run-time... SLIGHTLY.
If you want to increase runtime, there are better ways of doing that.

 

[EpicHam]

And a 15 gallon tank holds more fuel than a 10 gallon tank. It does NOT make the car better.
You forgot to read the first part of my post entirely. That only serves to increase run-time... SLIGHTLY.
If you want to increase runtime, there are better ways of doing that.

Umm...
Copper holds more heat , higher heat conductivity and thus higher radiation speed

Are we gonna go into one of those arguments again?

 

[EpicHam]

WE got to wrap this up...
ONCE AND FOR ALL!!

This topic has popped up again and again and again and again for like 5 years now!!

Let's TURN THIS INTO HELIUM!!

I am sending this question to a physicist at NASA
cosmicopia@cosmicra.gsfc.nasa.gov

Updates coming.... sooner or later

On second thought , I don't think we need to send an email to NASA anymore lol

In the meantime , please entertain yourself with this research done by QATS Advanced Thermal Solution . Inc
http://www.ecnmag.com/articles/2010...erent-heat-sink-materials-cooling-performance

Copper and aluminium performed similarly under a convective environment, but as the rate of airflow increased .
Copper's lower thermal resistance triumphed.

PS: Its more of a research to sell their Carbon foam , so you really have to dig.

Alumnium heatsink

Copper Heatsink

Comparison of temperature distribution of both heatsink

Final heatsink performance chart

 

[TheDukeAnumber1]

Umm...
Copper holds more heat , higher heat conductivity and thus higher radiation speed

Are we gonna go into one of those arguments again?

He wasn't saying aluminum is better thermally, he knows this. Your jumping the gun there buddy.

 

[EpicHam]

He wasn't saying aluminum is better thermally, he knows this. Your jumping the gun there buddy.

 

[ApexProxy]

I find it funny this argument is going again. It is fact that copper is thermally superior in every aspect to aluminum. The only reasons I use aluminum sometimes is because it is corrosion resistant, easier to work with, cheaper, lighter, and can be anodized to look cool. But thermally copper wins, hands down.

If anyone wants to do their own research look up Volumetric Heat Capacity and Thermal Conductivity.

 

[EpicHam]

I find it funny this argument is going again. It is fact that copper is thermally superior in every aspect to aluminum. The only reasons I use aluminum sometimes is because it is corrosion resistant, easier to work with, cheaper, lighter, and can be anodized to look cool. But thermally copper wins, hands down.

If anyone wants to do their own research look up Volumetric Heat Capacity and Thermal Conductivity.

Trust me , in a few weeks a thread like this is going to pop up again .

 

[ApexProxy]

Trust me , in a few weeks a thread like this is going to pop up again .

I don't doubt that. I'm going to bookmark this thread for when that time comes.

 

[Cyparagon]

copper is thermally superior in every aspect to aluminum.

And 1 gauge wire is electrically superior in every aspect to 26 awg. But there are some obvious reasons why we don't use 1 gauge in everything.

 

[ApexProxy]

And 1 gauge wire is electrically superior in every aspect to 26 awg. But there are some obvious reasons why we don't use 1 gauge in everything.

Which is where this part of that post comes in:
"The only reasons I use aluminum sometimes is because it is corrosion resistant, easier to work with, cheaper, lighter, and can be anodized to look cool."

 

[Leodahsan]

Aluminum better for:
lower cost
smaller heatsinks
enclosed systems
anodizing
better look when exposed

Copper better for:
Convection cooling
Conducting heat on longer heatsink fins (better for bigger heatsinks)
exposed systems
(bad when exposed, tarnishes)

Problem solved? People can figure all of that by theirselves, I can't see why the discussion here... :thinking:
at least lets be more friendly when discussing.

IE, one could get two thick strands of copper and aluminum wire and heat both at a stove and see what conducts heat better.
One could attach power resistors to copper and AL heatsinks and turn both on @ constant power and see what performs better.

Trust me , in a few weeks a thread like this is going to pop up again

Just post there, link to this thread, and forget it. It happens everyday, its the beauty of the forums. People are allowed to post whatever they want! And solving all problems in a single thread and stickying it will not solve the problem.

 

[hwang21]

Sooo... taking a new step in this thread (but not to thread jack), it looks like Rick Trent is getting hold of some copper heatsinks for his 3.5W 445nm's... the current ones use aluminum. I'm assuming that copper is the better option here? Aside from corrosion?

 

[Leodahsan]

For cooled systems, exposed heatsink systems, or some kind of TEC or watercooling systems, it should be.

 

[ApexProxy]

Actually copper is superior for small heatsinks as well as enclosed systems. Its also superior for large heatsinks equally as much. Think about it. It takes longer to heat up and cools faster while pulling heat away from the diode faster as well. In a nutshell, its thermally superior in every way.

Rick Trent using copper in the lasers is an improvement if you do not mind the corrosion tendencies. My favorite solution to that issue is gold plating. The downsides being cost and that gold is not as good at thermal conduction as copper but still superior to aluminum. Its volumetric heat capacity is irrelevant due to the extremely low volume used(still slightly better than aluminum though ).