[barnz0432]

I was just wondering if you have to use copper to build an evap ?

The blacksmith that is going to lathe it for "free" said that aluminum is a better metal for heat transfer then copper.

I was wondering if that were true.


tell me what you think.

[Pf.Farnsworth]

He is wrong.
Copper has a greater heat transfer coefficient.

There are a few substances that are at the top of the thermal conductivity charts, namely:

* Diamond (2300 W/mK)
* Pyrolytic Graphite (1950 W/mK)
* Silver (429 W/mK),
* Pure Copper (401 W/mK), and
* Pure Aluminum (237 W/mK).

http://www.overclockers.com/articles223/index02.asp

At very low temperatures, we are talking -190C and lower, there is a phenomenon with free electrons. Some materials will have increaced thermal conductivity. However there are problems with that as well. Our inquiry in to the matter on xtremesystems ended or paused for now with this conclusion, formulas provided below.

I spent a little tim reading the data and the Wiedemann-Franz Law, basically it says that thermal conductivity is proportional to the free electrons since both electrical conductivity and thermal conductivity use "electron fog" or the available electrons to conduct, However as temperature increases thermal conductivity increases due the available energy level of the electrons peresent and the same applies to electrical conductivity as the free electrons need more potential to be pushed from thier orbit at higher temperatures. At lower temperatures he inverse is true. Ok I got ya I was suprised that the difference betweel 0C and -100C was so small. So the best material to build a block out of would be one that had a negitive temperature coeffecient. where it would increase in electrical conductivity as temperature unfortunatly all these materials currently availaible are also not good conductors to begin with...

[barnz0432]

thank you for your reply

I will pass on the info to him and just order my solid chunk of copper to make my evap

[4GHZ_or_bust]

Why not order silver instead? Better heat transfer according to the numbers. Just grab your grandmother's silverware, melt 'em and use 'em.

just kidding. Silver isn't cheap in any case.

[LabRat23]

Aluminum gives the illusion that it has better heat transfer because if you hold two equally long rods in a flame, aluminium will burn your fingers faster than copper will. What causes this is aluminium's very low heat capacity, so it takes very little heat to make aluminum hot. This doesn't matter in a heatsink because in a heatsink we are dealing with a steady state and it is not how fast it heats up that matters but the volume of heat it will carry.

[Pf.Farnsworth]

I am thinking about making a silver block actually. I was qurious about the price. I can do the work myself but I have never checked what the price is on silver. I can go down to the machine shop I used to work at but I dont feel like going there just to bother them with questions lol.

If its around 100$ for a 3" x 3" bock I wouldnt mind.

[4GHZ_or_bust]

3 inch by 3 inch, assuming one inch thick will set you back about $400 in silver alone!

Silver is currently $7.37/oz and from research on the web, silver is 0.378 pounds per cubic inch.

9 cubic inch = 3.4 pounds of silver * 16 oz/lbs = 54.4 oz. Total: $400.93

.

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[torin3]

Originally Posted by 4GHZ_or_bust

3 inch by 3 inch, assuming one inch thick will set you back about $400 in silver alone!

Silver is currently $7.37/oz and from research on the web, silver is 0.378 pounds per cubic inch.

9 cubic inch = 3.4 pounds of silver * 16 oz/lbs = 54.4 oz. Total: $400.93

.

.

However, silver is sold by the troy ounce, which while it weighs more, is only 12 to the troy pound. Assuming your mass figures were in standard measurements, converting from the ounces it is 49.6 Troy oz. it is $365.55.

[Pf.Farnsworth]

~370, not to shabby. After I will finish my current project I will definetly pick up some silver and get to work. Thanks.

[4GHZ_or_bust]

When you carve out the block, do save all the silver scraps so you could resell and get some $$$ back.

Or just get a thin silver plate (like 1/4") for CPU contact and use copper or acrylia for the rest of the block.

[torin3]

Originally Posted by 4GHZ_or_bust

When you carve out the block, do save all the silver scraps so you could resell and get some $$$ back.

Definately! Hoover and Strong is a good place to do that http://www.hooverandstrong.com/

[Pf.Farnsworth]

I am actually thinking about a block with a diamond bottom. My friend is an electrical engineer, is a manager of the department so he can do some things for me. Apparently they use diamond heat spreader plates to cool their lasers in the lab. There has always been talk about diamond heatsinks and waterblocks but it doesnt occur to most people that just to have the bottom alone would reap dramatic results. Since diamond flows heat so well when you put a lets say a 2" x 2" x 1/16" diamond plate on lets say a mosfet that is 1/2" x 1/2" x 1/16" it saps all the heat out of the mosfet and now you are cooling an area that is 4 times as large which is a lot easier to dissipate heat from since there is 4 times the surface/contact area, something thats bluntly obvious when you talk about air cooling. He said it works great for their lasers and other experiments. He also said that they buy them in bulk mostly little once 1/8" x 1/8" x 1/16", each one costs $10. So not bad at all. He also said they might do a 2" x 2" x 1/16" for about $1000. Now the reason it would be so much is not because its hard to make or expensive. They have a standart that they charge 250$ an hour for their labour, and it takes just about 4 hours to take one of the shelf, package it, enter all the info in to their data base, and take it to the post office to ship. My friend gets theirs for $10 a peace because they buy them in bulk so the price per unit gets cut down hard. I had an idea of how to make good use of the small once to, he might be able to bring me some. We will see. When and if I go though with all this I will make a diamond cooling FAQ/Guide lol, hilarity ensued, making internet forum geek history.

[eobard]

Originally Posted by Pf.Farnsworth

When and if I go though with all this I will make a diamond cooling FAQ/Guide lol, hilarity ensued, making internet forum geek history.

Submit it as a front page article too, maybe you could recoup some of the costs. Also, I do think if you had such a sink that there would be a great demand from the masses to have it tested and ranked on the front page.

[Pf.Farnsworth]

I am very excited myself. Looking forward to alot of sleep-less nights and empty bank accounts. I go to collage full time and work full time so this wont happen tomorrow but I will try my best.

Being usefull to others is rewarding.