Computer case side fans...

Got my hammer out, and now I'm gonna open the box
JohnT
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Post by JohnT » 07/25/02, 12:10 am

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On 2002-07-17 19:22, Anonymous wrote:
Good scientific explanation but it it bothered me. I know something was a miss. The defination was correct but what you concluded, that "copper had almost twice the thermal conductance of aluminum" is based on analogy and not physics. As I have said the defination was correct but comparing the properties of
copper to aluminum cannot be done by linear scale.
It has to do with the amount current passed at a given voltage. What is true is that copper and Aluminum can be compared at a given voltage with current and it will produce the result you mentioned. Aluminum can handle quite a bit of current @ 120V before it begins to show signs of degradation that you described. Which is why only an improvement of 6 to 15% is achived using copper at working voltage/current levels in your computer case. At lower levels of voltage/current aluminum is almost as stable.

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Hope you don't have a lot of current going through your heatsink. It could prove detrimental. 8)
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Post by AndrewB » 07/25/02, 11:09 am

oh yeah. everyone knows heat sinks cool by sending electricity through themselves directly over the aluminum or copper die of the CPU... {eyes rolling}

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Post by SOD » 07/25/02, 9:24 pm

Andrew before you spout off about one more thing YOU DON"T KNOW take a basic course in physics, then a basic course in electronics. You are very monolithic. Energy can be viewed from different perspectives within the same relm. Volts, Current, Joules, and Watts. Watts (P=IE) are what we are talking here or the ability dissipate energy which in this state is heat you are actually venting an excess ratio of volts to current. Computer chips are not energy efficent. In other words excess voltage and excess current are dissipated (converted) as heat you can measure the device dissipation in this case, the heat sink by increasing the voltage and current of the device the heat sink is attached to and measuring the thermal output of the heat sink. So yes you are passing an electrical current and voltage through the sink just ina different state. And yes you can measure by passing voltage and current through a given material. They do that all the time to design anything that dissipates or interacts with energy.
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Post by AndrewB » 07/26/02, 5:36 am

but as I said, there's no current going through the sink itself.
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Post by SOD » 07/26/02, 7:35 am

Yes there is, it is in a different state. You can't view thermal exchange in a electrical device without first considering that. What happens if the current is in creased to the device? The amount of watts being passed to tthe sink increases. It is all the samething.

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Post by AndrewB » 07/26/02, 8:22 am

ok. you win, I loose, flamewar over.
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Post by JohnT » 07/26/02, 10:09 am

"No, I'm the richest man in the world". (Mel Brooks,Life Stinks)
"A man may be a fool and not know it, but not if he is married."

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Post by SOD » 07/26/02, 10:10 am

No it is not a "flamewar" just science. Here is another example: When you listen to sound in a radio you are listening to the power supply of the circut, volts and amps. They are generated by battery or perhaps 120V @15amps common u.s. household current. I have a sound system that when the preamp is plugged into the wall out of phase or backwards it effects the image of the sound, it becomes flat. I guess the point I am trying to make to you is that when you consider anything electrical go where the source starts. The basic computer supply recomended does not even begin to scrach the surface for filtering and monitoring of supply line both from a quantative or qualatative perspective.

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Post by AndrewB » 07/26/02, 12:25 pm

I guess... But I think there was some confusion. I wasnt referring to how much heat was caused by the electronic unit in question (or if it does at all), I was saying that a live electric current isnt running through the heat sink itself, just the fan if it has one.
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Post by RedRage » 07/26/02, 3:02 pm

I think (some times i do that and i always write it on the calander) the confusion is that SOD is talking bout Energy (in this case heat given off by the chip) and Andy is talking about electricity.

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Post by Guest » 07/27/02, 4:20 am


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Post by Dark Shadow » 07/28/02, 3:37 pm

Anyone want to explain to me why Silver is a better heat conductor than Gold is but Gold is a better electric current conductor? You are limited to two pages or less and no words longer then seven sylables. :)

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Post by JohnT » 07/29/02, 12:16 am

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On 2002-07-28 23:37, Dark Shadow wrote:
Anyone want to explain to me why Silver is a better heat conductor than Gold is but Gold is a better electric current conductor? You are limited to two pages or less and no words longer then seven sylables. :)

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If you'll check out Thermal Conductivity 101 (couple of post above), you might be able to answer your own question.
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Post by bob » 07/29/02, 4:10 am

I love this thread....
WYSIWTF

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Post by SOD » 07/29/02, 1:05 pm

"Many people wonder why copper isn't widely used for heatsinks - copper has a thermal conductivity that's almost twice as high as the thermal conductivity of aluminum (393 W/mK, as opposed to 221 W/mK). However, the performance of a heatsink doesn't only depend on the thermal conductivity of the material, so a copper heatsink certainly won't be twice as efficient as a heatsink made of aluminum. Therefore, the better thermal characteristics of copper do not justify the significantly higher cost and other considerations (rigidity, weight). Also, copper is not very suitable for extrusion (which is the preferred production method for heatsinks - see page 3). However, there are some heatsink models that are made of copper and aluminum. Here, usually the base plate is made of copper (or has a copper inlay), and the fins are made of aluminum"

http://www.anandtech.com/showdoc.html?i=1115&p=2

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