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

Bruce Griffiths bruce.griffiths at xtra.co.nz
Sat Jul 12 23:19:19 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
The Taylor series expansion gives:

(T+h)^4 - T^4 = 4*h*(T^3) + 6*(h^2)*(T^2) + 4*(h^3)*T + h^4

The largest term of which is 4*h*T^3 for small h, and large T(absolute 

where ^ denotes the power of and * denotes multiplication.

That is for small temperature difference the radiative heat transfer is 
proportional to the PRODUCT of the temperature difference and the THIRD 
power of the absolute temperature.


More information about the time-nuts mailing list