In article ,
Martin Brown writes:
| Franz Heymann wrote:
|
| In fact, the cost does not vary exponentially, but is is roughly
| proportional to the desired temperature differential.
|
| Only in the draft proof ideal world of the physics lab.

Hmm. Until you get up to the point where radiation losses start
to be dominant, it is a pretty good approximation. All of the
usual causes of loss (including forced and unforced convection,
conduction, air and other material exchange etc.) are very close
to linear in the differential.

However, the cost CAN increase 'exponentially' when the desired
range is below the maximum external temperature, and there is no
cooling. This isn't because the losses aren't linear, but is an
artifact of the way that the cost is asymmetric.


Regards,
Nick Maclaren.