[time-nuts] Double ovened 10811-60158 on ebay

Bruce Griffiths bruce.griffiths at xtra.co.nz
Sat Jul 12 23:03:24 EDT 2008


Rick Karlquist wrote:
> Bruce Griffiths wrote:
>   
>> Mark Sims wrote:
>>     
>>> Remember that heat flow is proportional to the FOURTH power of the
>>> temperature difference.  Insulation is generally a linear function.  The
>>> combination makes thermal stabilization over even small ambient
>>> temperature ranges rather problematic.
>>>
>>>
>>>
>>>       
>> Nonsense.
>> The radiative transfer between 2 bodies at different temperatures is
>> proportional to the difference between the 4th powers of their absolute
>> temperatures.
>>     
>
> And this quantity is approximately equal to the THIRD power of
> the temperature difference for small temperature differences.
> (A simple calculus problem!)
>
> Rick Karlquist N6RK
>
>
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>   
Rick

For small temperature differences its always linearly proportional to 
the temperature difference not its third power.

Heat radiation is proportional to (T2)^4 - (T1)^4 which for small T2-T1 
~ (T2-T1)*T^3 where T ~ T1~T2 and T2-T1 is small.


Bruce



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