Doug Miller wrote:
In article , (David
Combs) wrote:
...
I recall from a thermodynaics course eons ago
that whatever the materials, the amount of heat
energy flowing from one to the other, per second,
is 100% *proportional* to the temperature *difference*
between the two.

With respect to conduction, yes...


It is also true for Newton's law of cooling which governs
conventive heat transfer. Radiant floor heating heats your
feet by conduction and the air in the room by convection.
Radiative heat transfer is negligible, the descriptor 'radiant'
is a misnomer, similar to the 'radiator' in a car.

....

This may come as a surprise to you, but if a 98.6-degree human sits
on an
80-degree block of steel, the direction of heat transfer is *from*
the human,
*to* the steel. Not the other way around. After thirty minutes
bareassed on
that block of steel, you're going to be shivering.


Agreed but with the caveat that 98.6 is the normal temp for under
your tongue. I dunno what the normal temperature is for your
butt cheeks.



Then, there's heating via radiation, like by a cast-iron
radiator, an electric (fanless) radiator, the sun, etc.

The first two examples heat by convection. Radiative heat
tranfer is negligible in a convective environment for such
small temperature differences. Even though readiative heat
transfer is proportionate the difference in the Fourth
Power of th eabsolute temperature, the coefficient is
typicall very small compared to the convective heat transfer
coefficient so that free convection dominates unless in a
weightless environment (but still dominates if there is a
fan), or a vaccuum.



Nice thing about cast-iron radiators is that you can
open the window, allowing nice (cold) fresh air to
circulate through the room somewhat, and yet you're
still warm (via the radiation).


I don't think so.

--

FF