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Re: re:Flow of energy



I had no intention of intervening into this discussion, but I
cannot resist to give my opinion, worth maybe 1/2 cent, about the
use and meaning of the word "heat"(the NOUN, and as used in PHYSICS,
not in "slang" or any version which is "in" at the present).
What is wrong in telling students just the simple truth??? For
example, to tell them that in many processes, like heat exchangers,
loss of heat through walls, calorimetric measurements, etc. etc.,
all happens AS IF "heat" would be some kind of fluid which can "flow"
from one object to another, obeying a conservation law? Of course,
in some other processes it does NOT obey the conservation law, as for
example when heat is generated by friction or released by a chemical
reaction. This shows, by the way, that this "heat" is equivalent to
a form of energy (without this equivalence the energy would not obey the law
of conservation!).
After all, students are expected to KNOW all the above and to use it
in all kinds of calculations easily. And they should be aware of the
kinds of processes where it applies and where it DOES NOT apply.
Also notice that the "diffusion" partial differential equation is
the same for the "flow" of heat and for the flow of water through
porous soil ("percolation"). But in this process there really IS a
moving fluid (the water), but it still does NOT percolates uniformly:
it really moves through the space inbetween solid particles, obeying
the Navier-Stokes equation. So, also in this case the macroscopic
description of the process is basically WRONG, but perfectly acceptable.
Regards Emilio