Jos,
I should have used it myself in mentioning the use of a copper spreader where
it has
less thermal resistance than aluminum. Thermal resistance comes into play in
the
design of a heatsink also. Wikipedia has some really good info on thermodynamics
with links from one item to the next on each page.
http://en.wikipedia.org/wiki/Convection
http://en.wikipedia.org/wiki/Heat_conduction
http://en.wikipedia.org/wiki/Thermal_radiation
http://en.wikipedia.org/wiki/Thermal_conductivity
http://en.wikipedia.org/wiki/Heat_Transfer
http://en.wikipedia.org/wiki/Thermodynamics
Best,
Will
*********** REPLY SEPARATOR ***********
On 8/18/06 at 8:48 AM hermans wrote:
>Hey Will,
>
>I follow this treat with one eye and one ear...... I wonder why I no one
>used the terminology " termal resistance " used in heath transfer formulas.
>Have a good day Will.
>73
>
>Jos on4kj os5n
>
>
>**************************************************
>
>-----Message d'origine-----
>De : amps-bounces@contesting.com [mailto:amps-bounces@contesting.com] De la
>part de Will Matney
>Envoyé : jeudi 17 août 2006 21:29
>À : garyschafer@comcast.net; amps@contesting.com
>Objet : Re: [Amps] Anodizing aluminum, painting etc.
>
>
>Gary,
>
>Correct, I don't think anyone is saying this isn't so. I know the fins are
>what make up the large surface area and are what dissapate the heat to the
>atmosphere. The mass of the solid portion merely helps as far as heat up
>time and the spreading of the heat through the heatsink. Generally the ones
>used for RF power transistors are around 0.200 to 0.250 thick. One can use
>a
>copper spreader to make the heat spread more quickly to be dissapated. The
>problem arises with the color and the anodized coating which can act as an
>insulator, and also absorb heat from an IR radiating source. I'm going to
>try and investagate this later today, and see what I find about the use of
>black on heatsinks. I'll let everyone know what I dig up.
>
>Best,
>
>Will
>
>*********** REPLY SEPARATOR ***********
>
>On 8/17/06 at 12:42 PM Gary Schafer wrote:
>
>>Some of the confusion about heat sinks I think comes from referring to
>>"mass" of the sink. Mass is really the same thing as weight. Weight of
>>a sink by itself has no real effect on its ability to dissipate heat.
>>If it did then lead would probably be the desired material. Each type
>>of material has its own thermal conducting characteristics. Aluminum
>>happens to be quite good at it.
>>
>>A heat sink is really a heat exchanger just like an air conditioner.
>>Making the heat sink heavier by making it a larger block doesn't
>>necessarily make it a better heat sink. Larger will hold more heat but
>>it is surface area that gets rid of the heat.
>>
>>Think of a heat sink as a surface transformer. It effectively enlarges
>>the surface area of a device.
>>
>>73
>>Gary K4FMX
>>
>>
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>
>
>
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