mm wrote:
In high school physics, the three methods of heat dispersal were
presented as conduction, radiation, and convection?

Is that all there is? Is diffusion a fourth or is it subsumed by
convection?

That's a tricky question to answer. Partly, I don't understand what you
mean by 'dispersal'. In any case, heat can be transported by material
particles or by nonmaterial processes. That is, energy (heat) can be
convected by the motion of hot particles flowing into colder regions,
transported by infrared radiation, or transported by nonmaterial
diffusion (conduction). Hot particles diffusing into colder regions is
not typically found here on Earth due to bouyancy- hot stuff is less
dense and so there is a bouyancy-driven flow of material which convects
the heat.

I could be wrong but:
Conduction seems to be limited to within a solid, or from the surface
of a solid to that part of a liquid or gas in contact with the solid.

Only when bouyancy effects dominate. In space, for example, conduction
occurs in liquids and gases as well. Or if the liquid is of high
viscosity (if the Nusselt number is small). Thermal greases will
conduct heat rather than convect heat. There's also the Grashof number
and Peclet number. If these numbers are large or small, a particular
heat transfer mechanism occurs. For example, if the Grashof number is
large, there will be large bouyancy effects. If the Grashof number is
small, viscous effects dominate and the thermal energy will instead
diffuse.


ICBWB:
Convection seems to be limited to liquids and gases.

Yes, usually. Again, take away gravity and convection doesn't really
occur. There still are some effects like Marangoni flow (surface
tension-driven convection) that occur. It's an open question for
granular media, IIRC.


And ICBWB: radiation seems to be limited to from a solid or maybe a
liquid through a gas to another solid or maybe a liquid.

There's a difference between thermal radiation and radiative heat
transfer. You seem to be thinking about heat transfer here, not thermal
transport.

snip

--
Andrew Resnick, Ph.D.
Department of Physiology and Biophysics
Case Western Reserve University