>>> No.  The radiation of energy due to heat is proportional to the 
>>> fourth power of the absolute temperature.
> 
> Also your item receives radiation from other objects nearby, and of 
> course the amount depends on the temperature of them.

Which, I presume, means an object at thermal equilibrium emits and 
absorbs equal amounts of radiation.

>> And how about the conduction and/or convection of heat as a function 
>> of temparature difference?
> 
> Conduction is linear with temperature difference, convection is more 
> complex because it involves fluid flow.
> 
> Also, bear in mind that the thermal properties (specific heat, 
> conductivity, emissivity) will change significantly with temperature, so 
> it is really hard to give a straightforward function of temperature.

OK. Well when I did some simple experiments at school, we found that a 
glass of boiling water apporaches thermal equilibrium more or less 
logarithmically. So I think we can safely conclude that thermal losses 
increase at least linearly with temparature - even if the exact function 
is hard to pin down.

-- 
http://blog.orphi.me.uk/
http://www.zazzle.com/MathematicalOrchid*

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