Copper Heatsinks

[mlucitt]

I used water cooling in my computer. It worked well to draw the heat from the CPU. I pulled it out because it required a large fan to blow through the radiator and it was noisy. I went back to a typical CPU mounted fan.

 

[laatsch55]

Thought of Peltier straps??

 

[mlucitt]

I did think about peltier junctions but they didn't have the heat mass. They do make bigger ones but sheesh $$$$$$$.

 

[laatsch55]

Copper plate made it today, the strap didn't. I decided to do a set for a 400 first, just to see if we have any problems.

It will add another 17lbs to the weight of a 400 and 700.

 

[laatsch55]

Got off the phone with Ed a bit ago, and we have to correct thge thermal conductivity rating on copper vs aluminum. Copper is 97% more conductive than aluminum, or twice as conductive , not 5 times as I thought. Still, it's enough that the project is still going forward.

 

[speakerman1]

Got off the phone with Ed a bit ago, and we have to correct thge thermal conductivity rating on copper vs aluminum. Copper is 97% more conductive than aluminum, or twice as conductive , not 5 times as I thought. Still, it's enough that the project is still going forward.

Explain please. Doesn't area and thickness have something to do with it? Heat will also cause a higher rate of corrosion thus limiting the transference of heat. Ever thought of titanium or magnesium. Very good heat dissipation. Joe can you explain the theory of painting them black. Wouldn't you want it as porous as possible?

Larry

 

[laatsch55]

A black olbject radiates heat much better than any other color Larrt. I forget the property that makes it so. Thickness does to a certain extent then goes the other way(iirc), we're talking high school physics and that was awhile ago Larrt. I think copper was chosen for its thermal conductive qualities which, for easily obtainable materials is the best, if not THE best period.

 

[speakerman1]

Paint will fill the pours thus cutting down on its ability to stay cooler. Am I right. I forget the laws of thermodynamics. I did see where you make Vs on it to increase surface area. Black retains heat longer also. Something black will hold the heat longer than a lighter color. These are questions because I am trying to understand.

Larry












/

 

[laatsch55]

Now is the time for Joe to input.

 

[speakerman1]

Got off the phone with Ed a bit ago, and we have to correct thge thermal conductivity rating on copper vs aluminum. Copper is 97% more conductive than aluminum, or twice as conductive , not 5 times as I thought. Still, it's enough that the project is still going forward.

What do you mean the correct thermal conductivity rating? I'm not trying to be a jerk about the painting. I am trying to understand.

Larry

 

[Skratch]

Sometimes at work when we have a mold that we want to run balls out we make it out of beryllium copper instead of aluminum for cooling purposes. It machines well and is a lot stronger than copper and the drawback is cost.

 

[mlucitt]

Beryllium copper is what tools are made of that are required for work on nuclear weapons because they are strong and will not spark. Don't ask me how I know this...

 

[laatsch55]

Got off the phone with Ed a bit ago, and we have to correct thge thermal conductivity rating on copper vs aluminum. Copper is 97% more conductive than aluminum, or twice as conductive , not 5 times as I thought. Still, it's enough that the project is still going forward.

What do you mean the correct thermal conductivity rating? I'm not trying to be a jerk about the painting. I am trying to understand.

Larry

Whoa Larrt, didn't think you were Bud. Ed was wrong about bhow much better copper conducts than aluminum is all. he thought it was 5 times as fast, but after checking his facts it was only 2 times .

 

[Gepetto]

Not painting, black oxide or black anodize for aluminum. Painting will reduce heatsink effectiveness.

 

[Gepetto]

These are chemical treatments, not paint treatments.

 

[laatsch55]

Gotcha.

 

[Gepetto]

Stefan-Boltzman law describes radiative heat transfer:

Prad = 5.7 * 10^-8 * E * A * [(Ts)^4 - (Ta)^4] in watts
where:

E = emissivity
black anodized aluminum E = 0.9
polished aluminum E = 0.05

A = surface area (m2) through which heat radiation emerges

Ts = surface temperature (K) of component
Ta = ambient temperature (K)"

 

[laatsch55]

Big difference in the anodized and polished----WOW.

 

[speakerman1]

Copper heatsinks will help keep semiconductor heat down Lee because copper conducts heat and electrical current better than aluminum but difficult to say without more rigorous analysis whether the improved conductivity benefit is enough to avoid forced air cooling under your conditions. Putting a black oxide finish on the copper will help the copper radiate into the air more efficiently but still don't know whether it will be enough. The copper will help keep all portions of the heatsink at closer to the same temperature than the aluminum (in other words, the aluminum will exhibit a larger temperature gradient from transistor to tips of the heat sink fins)

Sorry Joe I forgot you said oxide. Now that makes a world of difference.

Larry

 

[mlucitt]

Lee,
You could try this stuff:

http://www.dickblick.com/products/liver ... ng.com+Inc.