Another question to those who say that energy can not flow. Suppose you
have two identical metallic cubes wrapped in styrofoame. Tiny thermometers
inserted into them indicate different temperatures. Suppose that the inner
energy of the cube A is 10000 J while that of cube B is 9000 J. We all know
what happens when A and B are put in contact with each other, again inside
a thick layer of styrofoam. After some time, perhaps 10 or 100 minutes, the
internal energy of each block is nearly 9500 J.
Why is it bad physics to say that there is a flow of 500 J of energy, from
cube A to cube B, during the equilibrating process? Also give one or two
illustrations in which the "energy flow" term is wrongly used. Seeing
physical situations in which the energy flow idea is not applicable will
help to understand your reservation.
Ludwik Kowalski