[Milsurplus] GRC109/R-1004A arrived!

[J. Forster]

Look, the heat dissipation by convection and radiation isapproximately:

Q/A = (Film Coefficient)(Temp Diff) + (Sigma)(View Factor){(Abs HS
Temp)^^4 - (Abs Amb Temp)^^4}



Film Coefficient varies with air flow speed
Temp Diff = Heat Sink Surface Temp - Ambient Air Temp
Sigma = Stefan-Boltzman constant
View Factor = fraction ofd HS that can see ambient **
Abs HS Temp = Absolute (K or R) of HS
Abs Amb Temp = Absolute (K or R) of environment surfaces (like room walls)


** View Factor of a flat plate is about 0.5; of a finned HS far less.

-John

====================






> According to the AAVID/Thermalloy website:
>
> "Heat sinks cooled by natural convection may benefit from an anodized
> finish, but the added cost of the finish may not be justified when the
> part is used in forced convection cooling.
> Surface emissivity limits the amount of heat transfer due to radiational
> cooling. With 1.0 being perfect (black body) emissivity anodized
> aluminum is 0.85 and unfinished is 0.05."
>
> This could explain why early mobiles like the Motorola T-power had black
> heatsinks and relied solely on convection whereas computers & test
> equipment with fans use plain.
>
> Perhaps the designer of the RS1/GRC109 thought that because the unit was
> sealed that there was enough heat generated by the vacuum tubes to
> warrant better thermal dissipation.
> Then again black is harder to spot. The later replacement RS6 is black
> as well but well ventilated. A lot of the WW2 spy sets were available in
> black only (standard spy colour).
>
> Bruce   ve7mt
>
>
>
> On 9/14/2011 5:15 PM, John Hutchins wrote:
>> All -
>> Black heat sinks seem to dissipate, distribute, suck off, more heat from
>> the device; when looking at the heat sink specifications.
>> I believe units painted  the Black in WW2/Korea/Viet Nam was:
>>    1. cheap paint.
>>    2. for light, reflection, glint, abatement
>> Now I could be wrong.... being anything with a tube ran hot anyway.
>> Hutch
>>
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